Method for predicting expansion and shrinkage during solidification of mg-zr based alloys
By constructing a prediction model for expansion and contraction rates based on zirconium content, the problem of inaccurate control of expansion and contraction rates during the solidification of Mg-Zr alloy melts was solved, thereby improving the quality and yield of magnesium alloy castings.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NORTH CHINA UNIVERSITY OF TECHNOLOGY
- Filing Date
- 2022-12-30
- Publication Date
- 2026-07-24
AI Technical Summary
In the existing technology, the expansion rate and shrinkage rate of Mg-Zr alloy melt during solidification cannot be accurately predicted and controlled, which affects the quality and yield of magnesium alloy castings.
By constructing a prediction model for expansion and contraction based on zirconium content, the expansion and contraction rates of magnesium alloys during the liquid phase and solidification processes are predicted, including linear variation models of liquid phase expansion, solidification expansion, liquid phase contraction, and solidification contraction.
It enables accurate prediction of the expansion and shrinkage rates during the solidification process of Mg-Zr alloy melts, supporting the refined formulation and improvement of casting processes, and improving casting quality and yield.
Smart Images
Figure CN116150974B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the fields of metallurgical technology, metallic materials technology, and casting technology, and in particular to a method for predicting the expansion rate and shrinkage rate during the solidification process of Mg-Zr alloys. Background Technology
[0002] Most magnesium alloy products are produced through conventional casting. However, with the expansion of magnesium alloy applications, higher demands are being placed on the production of thin-walled, complex, and large castings. Consequently, the requirements for refined management and improvement of casting processes, especially in the control of casting defects, are gradually increasing.
[0003] Porosity, shrinkage cavities, and hot cracks are common casting defects that significantly affect the quality and yield of magnesium alloy castings. These defects are closely related to solidification behaviors such as liquid feeding and solidification shrinkage during the solidification process of magnesium alloy melts. Therefore, quantitative prediction of the solidification behavior of magnesium alloy melts can support the precise control of the number and probability of casting defects during the solidification process, thus providing technical reference for the formulation and improvement of casting processes.
[0004] On the other hand, the solidification behavior of magnesium alloy melts is closely related to the alloy composition. Adding different types of alloying elements to magnesium melts, as well as varying the content of these elements, will significantly alter the solidification behavior of magnesium alloys. Therefore, establishing a quantitative relationship between the types and contents of alloying elements and the solidification behavior of magnesium alloys is fundamental to accurately and rationally formulating or improving magnesium alloy casting processes and producing high-quality magnesium alloy castings.
[0005] Zirconium (Zr) is one of the important alloying elements added to commercial magnesium alloys such as Mg-Zn-Zr, which are used in various fields. The addition of Zr and different Zr contents have a significant impact on the solidification behavior of magnesium alloy melts. Therefore, it is crucial to quantitatively characterize the effect of Zr content on the solidification behavior of magnesium alloy melts and to develop a method for predicting the solidification behavior of magnesium alloy melts based on the Zr content in the melt.
[0006] The solidification behavior of magnesium alloy melts is mainly manifested in their expansion and contraction during solidification. This invention provides a method for predicting the expansion and contraction rates of magnesium alloys during solidification based on their Zr content. This method can provide technical support and data support for the formulation and improvement of Zr-containing magnesium alloy casting processes, as well as for improving the quality and yield of Zr-containing magnesium alloy castings. Summary of the Invention
[0007] This invention addresses the problem that the expansion and contraction behavior during the solidification process of Zr-containing magnesium alloy melts has not been given sufficient attention, and the corresponding expansion and contraction rates cannot be accurately predicted and controlled. It provides a method for predicting the expansion and contraction rates during the solidification process of Mg-Zr alloys. Based on the Zr content of the magnesium alloy, it achieves quantitative and accurate prediction of the expansion and contraction behavior during the solidification process of the magnesium alloy melt.
[0008] To achieve the above objectives, the present invention provides the following solution:
[0009] Methods for predicting the expansion and shrinkage rates during the solidification of Mg-Zr alloys include:
[0010] The zirconium content in the magnesium alloy is determined, the magnesium alloy is melted, and the melted magnesium alloy is poured into a mold cavity for solidification.
[0011] During the solidification process, expansion rate prediction model and shrinkage rate prediction model are constructed based on the zirconium content, respectively.
[0012] Based on the expansion rate prediction model and the shrinkage rate prediction model, the expansion rate and shrinkage rate of the magnesium alloy are predicted.
[0013] Preferably, determining the zirconium content in the magnesium alloy, melting the magnesium alloy, and pouring the melted magnesium alloy into a mold cavity for solidification includes:
[0014] When the weight percentage of zirconium in the magnesium alloy is not greater than 2.00%, pure magnesium is melted in a crucible at the conventional casting temperature of the magnesium alloy, magnesium-zirconium intermediate alloy block is added to the crucible, stirred, and a protective gas is introduced during the addition and stirring process to obtain the smelted magnesium alloy.
[0015] The smelted magnesium alloy is added to a flux for refining, slag removal is completed, and the protective gas is introduced during the refining and slag removal process to obtain a melt, which is then poured into a mold cavity for solidification.
[0016] Preferably, the solidification process includes:
[0017] The magnesium alloy undergoes expansion, and after the expansion ends, it begins to contract until the solidification process of the magnesium alloy is completely finished.
[0018] The expansion behavior includes liquid phase expansion behavior and solidification expansion behavior, and the contraction behavior includes liquid phase contraction behavior and solidification contraction behavior.
[0019] Preferably, based on the expansion rate prediction model, predicting the expansion rate of the magnesium alloy undergoing liquid phase expansion includes:
[0020] Based on the first extreme point of the expansion rate variation range, the second extreme point of the expansion rate variation range, the slope of the linear change of expansion rate with zirconium content, and the intercept of the linear change of expansion rate with zirconium content, an expansion rate prediction model for the liquid phase expansion behavior is constructed. When the weight percentage of zirconium in the magnesium alloy is not greater than 0.35%, the linear change of expansion rate in the liquid phase expansion behavior is obtained through the expansion rate prediction model for the liquid phase expansion behavior, and the expansion rate of the magnesium alloy undergoing liquid phase expansion behavior is predicted.
[0021] The first extreme point of the expansion rate variation range is 0.350‰, the second extreme point of the expansion rate variation range is 0.250‰, the slope of the linear change of expansion rate with zirconium content is -28.994, and the intercept of the linear change of expansion rate with zirconium content is 0.360‰.
[0022] Preferably, based on the expansion rate prediction model, predicting the expansion rate of the magnesium alloy during solidification expansion further includes:
[0023] Based on the first extreme point of the expansion rate variation range, the second extreme point of the expansion rate variation range, the slope of the linear change of the expansion rate with zirconium content, and the intercept of the linear change of the expansion rate with zirconium content, an expansion rate prediction model for the solidification expansion behavior is constructed. When the weight percentage of zirconium in the magnesium alloy is greater than 0.35% and less than or equal to 1.10%, the linear change of the expansion rate in the solidification expansion behavior is obtained through the expansion rate prediction model for the solidification expansion behavior, and the expansion rate of the magnesium alloy undergoing solidification expansion behavior is predicted.
[0024] The first extreme point of the expansion rate variation range is 0.250‰, the second extreme point of the expansion rate variation range is 0.510‰, the slope of the linear change of expansion rate with zirconium content is 27.041, and the intercept of the linear change of expansion rate with zirconium content is 0.207‰.
[0025] Preferably, predicting the expansion rate of the magnesium alloy during solidification expansion further includes:
[0026] Based on the first extreme point of the expansion rate variation range, the second extreme point of the expansion rate variation range, the slope of the linear change of the expansion rate with zirconium content, and the intercept of the linear change of the expansion rate with zirconium content, an expansion rate prediction model for the solidification expansion behavior is constructed. When the weight percentage of zirconium in the magnesium alloy is greater than 1.10% and less than or equal to 2.00%, the linear change of the expansion rate in the solidification expansion behavior is obtained through the expansion rate prediction model for the solidification expansion behavior, and the expansion rate of the magnesium alloy undergoing solidification expansion behavior is predicted.
[0027] The first extreme point of the expansion rate variation range is 0.510‰, the second extreme point of the expansion rate variation range is 0.090‰, the slope of the linear change of expansion rate with zirconium content is -44.231, and the intercept of the linear change of expansion rate with zirconium content is 0.977‰.
[0028] Preferably, the method for obtaining the linear change of the expansion rate in the liquid phase expansion behavior or the solidification expansion behavior is as follows:
[0029] ye = kex + be
[0030] Among them, y e Let x be the expansion rate, x be the zirconium content in the magnesium alloy, and k be the expansion coefficient. e b is the slope of the linear model of expansion rate with zirconium content. e This is the intercept of the linear expansion rate model with zirconium content.
[0031] Preferably, based on the shrinkage prediction model, predicting the shrinkage rate of the magnesium alloy undergoing liquid phase shrinkage includes:
[0032] Based on the first extreme point of the shrinkage rate variation range, the second extreme point of the shrinkage rate variation range, the slope of the linear change of shrinkage rate with zirconium content, and the intercept of the linear change of shrinkage rate with zirconium content, a shrinkage rate prediction model for the liquid phase shrinkage behavior is constructed. When the weight percentage of zirconium in the magnesium alloy is not greater than 0.35%, the linear change of shrinkage rate in the liquid phase shrinkage behavior is obtained through the shrinkage rate prediction model for the liquid phase shrinkage behavior, and the shrinkage rate of the magnesium alloy undergoing liquid phase shrinkage behavior is predicted.
[0033] The first extreme point of the shrinkage rate variation range is 0.450‰, the second extreme point of the shrinkage rate variation range is 0.750‰, the slope of the linear change of the shrinkage rate with zirconium content is 12.800, and the intercept of the linear change of the shrinkage rate with zirconium content is 0.596‰.
[0034] Preferably, the shrinkage rate for predicting the solidification shrinkage behavior of the magnesium alloy includes:
[0035] Based on the first extreme point of the shrinkage rate variation range, the second extreme point of the shrinkage rate variation range, the slope of the linear change of the shrinkage rate with zirconium content, and the intercept of the linear change of the shrinkage rate with zirconium content, a shrinkage rate prediction model for the solidification shrinkage behavior is constructed. When the weight percentage of zirconium in the magnesium alloy is greater than 0.35% and less than or equal to 2.00%, the linear change of the shrinkage rate in the solidification shrinkage behavior is obtained through the shrinkage rate prediction model for the solidification shrinkage behavior, and the shrinkage rate of the magnesium alloy undergoing solidification shrinkage behavior is predicted.
[0036] The first extreme point of the shrinkage rate variation range is 0.100‰, the second extreme point of the shrinkage rate variation range is 0.780‰, the slope of the linear change of the shrinkage rate with zirconium content is 23.609, and the intercept of the linear change of the shrinkage rate with zirconium content is 0.306‰.
[0037] Preferably, the linear change in the shrinkage rate during the liquid phase shrinkage behavior is as follows:
[0038] yls = klsx + bls
[0039] Among them, y ls k is the shrinkage rate of the liquid phase shrinkage behavior. ls Let be the slope of the linear model of shrinkage rate as a function of zirconium content in the liquid phase shrinkage behavior, where x is the zirconium content in the magnesium alloy, and b is the zirconium content. ls The intercept of the model for the linear change of shrinkage rate with zirconium content in the liquid phase shrinkage behavior;
[0040] The linear change in the shrinkage rate during solidification shrinkage is as follows:
[0041] yss=kssx+bss
[0042] Among them, y ss k is the shrinkage rate of solidification shrinkage behavior. ss Let x be the slope of the linear model of solidification shrinkage as a function of zirconium content, and b be the zirconium content in the magnesium alloy. ss The intercept of the model for the linear variation of shrinkage rate with zirconium content in solidification shrinkage behavior.
[0043] The beneficial effects of this invention are as follows:
[0044] This invention is applicable to the smelting and casting processes of conventional commercial magnesium alloys. By using the actual Zr content of the Mg-Zr alloy, it enables accurate prediction of the expansion and contraction rates during the solidification process of the alloy melt. This provides technical data support for refining or improving magnesium alloy casting processes, enhancing the quality and yield of cast products. This prediction method is not limited by the dimensions of the mold cavity, casting, or ingot. Attached Figure Description
[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0046] Figure 1 This is a flowchart illustrating the method for predicting the expansion and contraction rates during the solidification process of Mg-Zr alloys according to an embodiment of the present invention. Detailed Implementation
[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0048] Methods for predicting the expansion and shrinkage rates during the solidification of Mg-Zr alloys include:
[0049] The zirconium content in the magnesium alloy is determined, the magnesium alloy is melted, and the melted magnesium alloy is poured into a mold cavity for solidification.
[0050] During the solidification process, expansion rate prediction model and shrinkage rate prediction model are constructed based on the zirconium content, respectively.
[0051] Based on the expansion rate prediction model and the shrinkage rate prediction model, the expansion rate and shrinkage rate of the magnesium alloy are predicted.
[0052] Further, determining the zirconium content in the magnesium alloy, melting the magnesium alloy, and pouring the melted magnesium alloy into a mold cavity for solidification includes:
[0053] When the weight percentage of zirconium in the magnesium alloy is not greater than 2.00%, pure magnesium is melted in a crucible at the conventional casting temperature of the magnesium alloy, magnesium-zirconium intermediate alloy block is added to the crucible, stirred, and a protective gas is introduced during the addition and stirring process to obtain the smelted magnesium alloy.
[0054] The smelted magnesium alloy is added to a flux for refining, slag removal is completed, and the protective gas is introduced during the refining and slag removal process to obtain a melt, which is then poured into a mold cavity for solidification.
[0055] Furthermore, the solidification process includes:
[0056] The magnesium alloy undergoes expansion, and after the expansion ends, it begins to contract until the solidification process of the magnesium alloy is completely finished.
[0057] The expansion behavior includes liquid phase expansion behavior and solidification expansion behavior, and the contraction behavior includes liquid phase contraction behavior and solidification contraction behavior.
[0058] Furthermore, based on the expansion rate prediction model, the expansion rate predicted for the magnesium alloy exhibiting liquid phase expansion behavior includes:
[0059] The first extreme point A based on the range of expansion rate variation. e The second extreme point B in the range of expansion rate variation e The slope and intercept of the linear change of expansion rate with zirconium content are used to construct an expansion rate prediction model for the liquid phase expansion behavior. When the weight percentage of zirconium in the magnesium alloy is not greater than 0.35%, the linear change of expansion rate in the liquid phase expansion behavior is obtained through the expansion rate prediction model, and the expansion rate of the magnesium alloy when liquid phase expansion behavior occurs is predicted.
[0060] Wherein, the first extreme point A of the range of expansion rate variation e The second extreme point B of the expansion rate variation range is 0.350‰. e The slope of the linear change of the expansion rate with zirconium content is -28.994, and the intercept of the linear change of the expansion rate with zirconium content is 0.360‰.
[0061] Furthermore, based on the expansion rate prediction model, predicting the expansion rate of the magnesium alloy during solidification expansion also includes:
[0062] Based on the first extreme point A of the expansion rate variation range e The second extreme point B of the expansion rate variation range e The slope of the linear change of the expansion rate with zirconium content and the intercept of the linear change of the expansion rate with zirconium content are used to construct an expansion rate prediction model for the solidification expansion behavior. When the weight percentage of zirconium in the magnesium alloy is greater than 0.35% and less than or equal to 1.10%, the linear change of the expansion rate in the solidification expansion behavior is obtained through the expansion rate prediction model for the solidification expansion behavior, and the expansion rate of the magnesium alloy when solidification expansion behavior occurs is predicted.
[0063] Wherein, the first extreme point A of the range of expansion rate variation e The second extreme point B of the expansion rate variation range is 0.250‰. e The slope of the linear change of the expansion rate with zirconium content is 27.041, and the intercept of the linear change of the expansion rate with zirconium content is 0.207‰.
[0064] Furthermore, predicting the expansion rate of the magnesium alloy during solidification expansion also includes:
[0065] Based on the first extreme point A of the expansion rate variation range e The second extreme point B of the expansion rate variation range eThe slope of the linear change of the expansion rate with zirconium content and the intercept of the linear change of the expansion rate with zirconium content are used to construct an expansion rate prediction model for the solidification expansion behavior. When the weight percentage of zirconium in the magnesium alloy is greater than 1.10% and less than or equal to 2.00%, the linear change of the expansion rate in the solidification expansion behavior is obtained through the expansion rate prediction model for the solidification expansion behavior, and the expansion rate of the magnesium alloy when solidification expansion behavior occurs is predicted.
[0066] Wherein, the first extreme point A of the range of expansion rate variation e The second extreme point B of the expansion rate variation range is 0.510‰. e The slope of the linear change of the expansion rate with zirconium content is -44.231, and the intercept of the linear change of the expansion rate with zirconium content is 0.977‰.
[0067] Furthermore, the method for obtaining the linear change of the expansion rate in the liquid phase expansion behavior or the solidification expansion behavior is as follows:
[0068] ye = kex + be
[0069] Among them, y e Let x be the expansion rate, x be the zirconium content in the magnesium alloy, and k be the expansion coefficient. e b is the slope of the linear model of expansion rate with zirconium content. e This is the intercept of the linear expansion rate model with zirconium content.
[0070] Furthermore, A e and B e Which value is larger depends on whether the linear change is linearly increasing or linearly decreasing. If it's linearly increasing, then A... e e If it decreases linearly, then A e >B e In short, A e and B e The values refer to the two endpoints of the expansion rate variation range, or extreme points. Further, based on the shrinkage rate prediction model, the predicted shrinkage rate of the magnesium alloy undergoing liquid phase shrinkage includes:
[0071] The first extreme point A based on the range of shrinkage variation. ls The second extreme point B in the range of shrinkage rate variation ls The slope and intercept of the linear change in shrinkage rate with zirconium content are used to construct a shrinkage rate prediction model for the liquid phase shrinkage behavior. When the weight percentage of zirconium in the magnesium alloy is not greater than 0.35%, the linear change in shrinkage rate in the liquid phase shrinkage behavior is obtained through the shrinkage rate prediction model, and the shrinkage rate of the magnesium alloy when liquid phase shrinkage behavior occurs is predicted.
[0072] Wherein, the first extreme point A of the shrinkage rate variation range ls The second extreme point B of the shrinkage rate variation range is 0.450‰. ls The slope of the linear change in shrinkage rate with zirconium content is 12.800, and the intercept of the linear change in shrinkage rate with zirconium content is 0.596‰.
[0073] Furthermore, the shrinkage rate for predicting the solidification shrinkage behavior of the magnesium alloy includes:
[0074] Based on the first extreme point A of the shrinkage rate variation range ss The second extreme point B of the shrinkage rate variation range ss The slope of the linear change in shrinkage rate with zirconium content and the intercept of the linear change in shrinkage rate with zirconium content are used to construct a shrinkage rate prediction model for the solidification shrinkage behavior. When the weight percentage of zirconium element in the magnesium alloy is greater than 0.35% and less than or equal to 2.00%, the linear change in shrinkage rate in the solidification shrinkage behavior is obtained through the shrinkage rate prediction model for the solidification shrinkage behavior, and the shrinkage rate of the magnesium alloy when solidification shrinkage behavior occurs is predicted.
[0075] Wherein, the first extreme point A of the shrinkage rate variation range ss The second extreme point B of the shrinkage rate variation range is 0.100‰. ss The shrinkage rate is 0.780‰, the slope of the linear change of the shrinkage rate with zirconium content is 23.609, and the intercept of the linear change of the shrinkage rate with zirconium content is 0.306‰.
[0076] Furthermore, the linear change in the shrinkage rate during the liquid phase shrinkage behavior is as follows:
[0077] yls = klsx + bls
[0078] Among them, y ls k is the shrinkage rate of the liquid phase shrinkage behavior. ls Let be the slope of the linear model of shrinkage rate as a function of zirconium content in the liquid phase shrinkage behavior, where x is the zirconium content in the magnesium alloy, and b is the zirconium content. ls The intercept of the model for the linear variation of shrinkage rate with zirconium content in the liquid phase shrinkage behavior;
[0079] The linear change in the shrinkage rate during the solidification shrinkage behavior is as follows:
[0080] yss = kssx + bss
[0081] where y ss is the shrinkage rate of the solidification shrinkage behavior, k ss is the slope of the linear change model of the shrinkage rate of the solidification shrinkage behavior with respect to the zirconium content, x is the content of zirconium element in the magnesium alloy, and b ss is the model intercept of the linear change of the shrinkage rate of the solidification shrinkage behavior with respect to the zirconium content.
[0082] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0083] As Figure 1 ) shown, a method for predicting the expansion rate and shrinkage rate during the solidification process of Mg-Zr alloy system includes:
[0084] Determine the content of zirconium element in the magnesium alloy, melt the magnesium alloy, and pour the melted magnesium alloy into a cavity for solidification; during the solidification process, based on the content of the zirconium element, construct an expansion rate prediction model and a shrinkage rate prediction model respectively; based on the expansion rate prediction model and the shrinkage rate prediction model, predict the expansion rate and shrinkage rate of the magnesium alloy, specifically:
[0085] Further, the values of A e ), B e ), k e ), and b e vary according to the change of the Zr content x value of the alloy and are divided into the following cases:
[0086] When x ≤ 0.35% (weight percentage), A e is 0.350‰, B e is 0.250‰, k e is -28.994, and b is 0.360‰. At this time, the total expansion rate y e is the liquid phase expansion rate.
[0087] When 0.35% < x ≤ 1.10% (weight percentage), A e is 0.250‰, B e is 0.510‰, k e is 27.041, and b is 0.207‰. At this time, the total expansion rate y e is the solidification expansion rate.
[0088] When 1.10% < x ≤ 2.00% (weight percentage), A e is 0.510‰, B eis 0.090‰, k e is -44.231, b e is 0.977‰. At this time, the total expansion rate y e is the solidification expansion rate.
[0089] A e and B e respectively refer to the first extreme point and the second extreme point of the expansion rate change range.
[0090] Furthermore, the total shrinkage rate y ls ( / ‰) of the alloy liquid phase shrinkage stage changes linearly with the Zr content x (x ≤ 0.35% (weight percentage)) of the alloy. Among them, A ls and B ls , k ls and b ls values are 0.450‰, 0.750‰, 12.800 and 0.596‰ respectively. A ls and B ls [[ID=(2) A conventional pit-type resistance furnace is used to melt Mg-Zr magnesium alloys. Pure magnesium is melted in a covered iron crucible, with the crucible lid kept closed. After heating to 760–800°C, the lid is opened and the Mg-Zr master alloy block is added, preferably at 760–770°C. During the addition of the Mg-Zr master alloy block, stirring is required 2–4 times, and a protective gas (carbon dioxide or a mixture of carbon dioxide and sulfur hexafluoride) is circulated throughout the addition and stirring process to prevent oxidation, combustion, and burn-off of the furnace charge.
[0095] Furthermore, the stirring time in step (2) is 10 to 60 seconds each time.
[0096] (3) Hold the crucible at 750–800℃ for 10–20 minutes, with the lid closed during the holding period. After that, open the lid, add flux for refining, and then remove the slag. Protective gas is used throughout the refining and slag removal process to protect the melt from burning.
[0097] (4) When the crucible lid is closed, let the melt stand in the iron crucible for 5 to 20 minutes. When the melt temperature reaches 650°C to 800°C, open the lid and pour the melt. It is preferable to open the lid and pour the melt when the melt temperature is 680°C to 720°C.
[0098] (5) When pouring the melt described in step (4) into the mold cavity, a protective gas is passed through the entire process to protect the melt from burning and oxidation.
[0099] Furthermore, the casting mold described in step (5) is preheated to 200-300°C before casting.
[0100] Furthermore, in step (5), before casting, a protective gas is introduced into the cavity of the casting mold for 1 to 10 minutes.
[0101] Furthermore, the size of the casting mold cavity described in step (4) is not limited in this invention.
[0102] Furthermore, the protective gas mentioned above is carbon dioxide gas or a mixture of carbon dioxide and sulfur hexafluoride.
[0103] The prediction of the expansion and shrinkage rates during the solidification process of the Mg-Zr magnesium alloy prepared above includes the following:
[0104] After the melt is poured into the cavity of the casting mold, expansion and contraction behaviors will occur sequentially during the solidification process. This expansion behavior is not solely due to the decrease in melt temperature and the escape of gases, but is also primarily related to the crystallization evolution of the alloy's as-cast microstructure during solidification. The aforementioned expansion and contraction behaviors vary depending on the actual Zr content of the alloy (x, x≤2.00%).
[0105] (1) During the solidification process of the Mg-Zr series magnesium alloy melt, an expansion phenomenon occurs first.
[0106] When the Zr content x of the alloy ≤ 0.35% (weight percentage), the total expansion rate y of the alloy e ( / ‰) varies linearly within the range of 0.350‰ to 0.250‰. When the Zr content of the alloy melt is x1, the total expansion rate y during the solidification process of the alloy melt can be predicted e1 to be -28.994x1 + 0.360‰. At this time, this expansion behavior occurs in the liquid phase region, which is called the liquid phase expansion behavior; the corresponding total expansion rate is called the liquid phase expansion rate.
[0107] When the Zr content x of the alloy is: 0.35% < x ≤ 1.10% (weight percentage), the total expansion rate y of the alloy e ( / ‰) varies linearly within the range of 0.250‰ to 0.510‰. When the Zr content of the alloy melt is x2, the total expansion rate y during the solidification process of the alloy melt can be predicted e2 to be 27.041x2 + 0.207‰. At this time, this expansion behavior occurs in the solid-liquid two-phase region, which is called the solidification expansion behavior or the two-phase region expansion behavior; the corresponding total expansion rate is called the solidification expansion rate.
[0108] When the Zr content x of the alloy is: 1.10% < x ≤ 2.00% (weight percentage), the total expansion rate y of the alloy e ( / ‰) varies linearly within the range of 0.510‰ to 0.090‰. When the Zr content of the alloy melt is x3, the total expansion rate y during the solidification process of the alloy melt can be predicted e3 to be -44.231x3 + 0.977‰. At this time, this expansion behavior occurs in the solid-liquid two-phase region, which is called the solidification expansion behavior or the two-phase region expansion behavior; the corresponding total expansion rate is called the solidification expansion rate.
[0109] Furthermore, the predicted expansion rate mentioned above is not restricted by the corresponding cavity of the casting mold, the size of the casting, or the ingot.
[0110] (2) After the expansion behavior during the solidification process of the Mg-Zr series magnesium alloy melt ends, a contraction behavior begins to occur.
[0111] When the Zr content x of the alloy ≤ 0.35% (weight percentage), the contraction behavior of the melt mainly occurs in the liquid phase region, which is called the liquid phase contraction behavior, and the corresponding total contraction rate is called the liquid phase expansion rate y ls ( / ‰). The liquid phase contraction rate y during the liquid phase contraction stage ls( / ‰) varies linearly within the range of 0.454‰ to 0.750‰. When the Zr content in the alloy melt is x1, the liquid shrinkage rate y during the solidification process of the alloy melt can be predicted. ls1 is 12.800x1 + 0.596‰.
[0112] When the Zr content x of the alloy is 0.35% < x ≤ 2.00% (weight percentage), the shrinkage behavior of the melt only occurs in the solid-liquid two-phase region, which is called the solidification shrinkage behavior or two-phase region shrinkage behavior, and the corresponding total shrinkage rate is called the solidification shrinkage rate or two-phase region shrinkage rate y. ss ( / ‰). The total shrinkage rate y during the solidification shrinkage stage ss ( / ‰) varies linearly within the range of 0.100‰ to 0.780‰. When the Zr content in the alloy melt is x4, the solidification shrinkage rate y during the solidification process of the alloy melt can be predicted. ss4 is 23.609x4 + 0.306‰.
[0113] Furthermore, the predicted shrinkage rate mentioned above is not restricted by the corresponding cavity of the casting mold, the size of the casting, and the ingot.
[0114] (3) When the shrinkage behavior during the solidification process of the Mg-Zr series magnesium alloy melt ends, the alloy solidification process ends and enters the solid-state shrinkage stage.
[0115] Prediction method for the expansion rate and shrinkage rate during the solidification process of Mg-Zr series alloys, specific implementation:
[0116] (1) Select 300 g of industrial pure magnesium blocks and place them in a covered iron crucible to melt in a pit-type resistance furnace. The crucible lid is always in the closed state;
[0117] (2) Weigh 7 g of Mg-30Zr master alloy blocks with a Zr content of 30% (weight percentage) to prepare Mg-Zr magnesium alloy with a Zr content of 0.23% (weight percentage).
[0118] (3) After heating the pure magnesium melt to 760 °C, open the lid and add Mg-30Zr (weight percentage) master alloy blocks. During the period of adding the Mg-30Zr master alloy blocks with the lid open, stir 3 times, 15 seconds each time. During the whole process of adding and stirring, pass a mixed gas of carbon dioxide + sulfur hexafluoride to protect the melt;
[0119] (4) After keeping the melt covered and holding it at 750 °C for 10 minutes, open the lid and add RJ-2 flux for refining, and then skim the slag. During the whole process of refining and skimming the slag, pass a mixed gas of carbon dioxide + sulfur hexafluoride to protect the melt.
[0120] (5) When the crucible lid is closed, let the melt stand in the iron crucible for 10 minutes. When the melt temperature reaches 710℃, open the lid and pour the melt into a rectangular casting mold.
[0121] (6) Before casting, the casting mold needs to be preheated to 250-300°C, and the mixture of carbon dioxide and sulfur hexafluoride gas should be introduced into the mold cavity 5 minutes before casting.
[0122] After the mold cavity is filled with the alloy melt, the solidification process begins. The total liquid phase expansion rate of the alloy melt during solidification is 0.285‰ (this value is a measured value including error). After the expansion ends and before the solidification ends, the alloy melt mainly undergoes liquid phase contraction, with a corresponding liquid phase contraction rate of 0.623‰ (this value is a measured value including error).
[0123] Changes in steps:
[0124] 1. The only difference is that in step (2), the Mg-30Zr intermediate alloy block is weighed at 33g to prepare a Mg-Zr magnesium alloy with a Zr content of 1% (by weight).
[0125] After the alloy melt fills the mold cavity, the solidification process begins. The total solidification expansion rate of the alloy melt during solidification is 0.480‰ (this value is a measured value including error). After the expansion ends and before the solidification ends, the alloy melt only undergoes solidification shrinkage, corresponding to a solidification shrinkage rate of 0.540‰ (this value is a measured value including error).
[0126] 2. The only difference is that in step (2), the Mg-30Zr intermediate alloy block is weighed at 56g to prepare a Mg-Zr magnesium alloy with a Zr content of 1.63% (by weight).
[0127] After the alloy melt fills the mold cavity, the solidification process begins. The total solidification expansion rate of the alloy melt during solidification is 0.256‰ (this value is a measured value including error). After the expansion ends and before the solidification ends, the alloy melt only undergoes liquid phase shrinkage, corresponding to a liquid phase shrinkage rate of 0.685‰ (this value is a measured value including error).
[0128] 3. The only difference is that in step (2), the Mg-30Zr intermediate alloy block is weighed at 76g to prepare a Mg-Zr magnesium alloy with a Zr content of 2.09% (by weight).
[0129] After the alloy melt fills the mold cavity, the solidification process begins. The total solidification expansion rate of the alloy melt during solidification is 2.280‰ (this value is a measured value including error). After the expansion ends and before the solidification ends, the alloy melt only undergoes liquid phase shrinkage, corresponding to a liquid phase shrinkage rate of 0.372‰ (this value is a measured value including error).
[0130] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.
Claims
1. A method for predicting the expansion and shrinkage rates during the solidification of Mg-Zr alloys, characterized in that, include: The zirconium content in the magnesium alloy is determined, the magnesium alloy is melted, and the melted magnesium alloy is poured into a mold cavity for solidification. During the solidification process, expansion rate prediction model and shrinkage rate prediction model are constructed based on the zirconium content, respectively. Based on the expansion rate prediction model and the shrinkage rate prediction model, the expansion rate and shrinkage rate of the magnesium alloy are predicted; Determining the zirconium content in the magnesium alloy, melting the magnesium alloy, and pouring the melted magnesium alloy into a mold cavity for solidification include: When the weight percentage of zirconium in the magnesium alloy is not greater than 2.00%, pure magnesium is melted in a crucible at the conventional casting temperature of the magnesium alloy, magnesium-zirconium intermediate alloy block is added to the crucible, stirred, and a protective gas is introduced during the addition and stirring process to obtain the smelted magnesium alloy. The smelted magnesium alloy is added to flux for refining, slag removal is completed, and the protective gas is introduced during the refining and slag removal process to obtain a melt. The melt is then poured into a mold cavity for solidification. The solidification process includes: The magnesium alloy undergoes expansion, and after the expansion ends, it begins to contract until the solidification process of the magnesium alloy is completely finished. The expansion behavior includes liquid phase expansion behavior and solidification expansion behavior, and the contraction behavior includes liquid phase contraction behavior and solidification contraction behavior. Based on the expansion rate prediction model, the expansion rate of the magnesium alloy undergoing liquid phase expansion behavior is predicted as follows: Based on the first extreme point of the expansion rate variation range, the second extreme point of the expansion rate variation range, the slope of the linear change of expansion rate with zirconium content, and the intercept of the linear change of expansion rate with zirconium content, an expansion rate prediction model for the liquid phase expansion behavior is constructed. When the weight percentage of zirconium in the magnesium alloy is not greater than 0.35%, the linear change of expansion rate in the liquid phase expansion behavior is obtained through the expansion rate prediction model for the liquid phase expansion behavior, and the expansion rate of the magnesium alloy undergoing liquid phase expansion behavior is predicted. Wherein, the first extreme point of the expansion rate variation range is 0.350‰, the second extreme point of the expansion rate variation range is 0.250‰, the slope of the linear change of expansion rate with zirconium content is -28.994, and the intercept of the linear change of expansion rate with zirconium content is 0.360‰; Based on the aforementioned expansion rate prediction model, predicting the expansion rate of the magnesium alloy exhibiting solidification expansion behavior further includes: Based on the first extreme point of the expansion rate variation range, the second extreme point of the expansion rate variation range, the slope of the linear change of the expansion rate with zirconium content, and the intercept of the linear change of the expansion rate with zirconium content, an expansion rate prediction model for the solidification expansion behavior is constructed. When the weight percentage of zirconium in the magnesium alloy is greater than 0.35% and less than or equal to 1.10%, the linear change of the expansion rate in the solidification expansion behavior is obtained through the expansion rate prediction model for the solidification expansion behavior, and the expansion rate of the magnesium alloy undergoing solidification expansion behavior is predicted. Wherein, the first extreme point of the expansion rate variation range is 0.250‰, the second extreme point of the expansion rate variation range is 0.510‰, the slope of the linear change of the expansion rate with zirconium content is 27.041, and the intercept of the linear change of the expansion rate with zirconium content is 0.207‰; The expansion rate for predicting the solidification expansion behavior of the magnesium alloy also includes: Based on the first extreme point of the expansion rate variation range, the second extreme point of the expansion rate variation range, the slope of the linear change of the expansion rate with zirconium content, and the intercept of the linear change of the expansion rate with zirconium content, an expansion rate prediction model for the solidification expansion behavior is constructed. When the weight percentage of zirconium in the magnesium alloy is greater than 1.10% and less than or equal to 2.00%, the linear change of the expansion rate in the solidification expansion behavior is obtained through the expansion rate prediction model for the solidification expansion behavior, and the expansion rate of the magnesium alloy undergoing solidification expansion behavior is predicted. Wherein, the first extreme point of the expansion rate variation range is 0.510‰, the second extreme point of the expansion rate variation range is 0.090‰, the slope of the linear change of expansion rate with zirconium content is -44.231, and the intercept of the linear change of expansion rate with zirconium content is 0.977‰; The method for obtaining the linear change of the expansion rate in the liquid phase expansion behavior or the solidification expansion behavior is as follows: ye =k ex +b e in, y e For expansion rate, x k represents the zirconium content in magnesium alloys. e b is the slope of the linear model of expansion rate with zirconium content. e This is the intercept of the linear expansion rate model with zirconium content.
2. The method for predicting the expansion and shrinkage rates during the solidification of Mg-Zr alloys according to claim 1, characterized in that, Based on the shrinkage rate prediction model, the predicted shrinkage rate of the magnesium alloy undergoing liquid phase shrinkage includes: Based on the first extreme point of the shrinkage rate variation range, the second extreme point of the shrinkage rate variation range, the slope of the linear change of shrinkage rate with zirconium content, and the intercept of the linear change of shrinkage rate with zirconium content, a shrinkage rate prediction model for the liquid phase shrinkage behavior is constructed. When the weight percentage of zirconium in the magnesium alloy is not greater than 0.35%, the linear change of shrinkage rate in the liquid phase shrinkage behavior is obtained through the shrinkage rate prediction model for the liquid phase shrinkage behavior, and the shrinkage rate of the magnesium alloy undergoing liquid phase shrinkage behavior is predicted. The first extreme point of the shrinkage rate variation range is 0.450‰, the second extreme point of the shrinkage rate variation range is 0.750‰, the slope of the linear change of the shrinkage rate with zirconium content is 12.800, and the intercept of the linear change of the shrinkage rate with zirconium content is 0.596‰.
3. The method for predicting the expansion and shrinkage rates during the solidification of Mg-Zr alloys according to claim 2, characterized in that, The shrinkage rate for predicting the solidification shrinkage behavior of the magnesium alloy includes: Based on the first extreme point of the shrinkage rate variation range, the second extreme point of the shrinkage rate variation range, the slope of the linear change of the shrinkage rate with zirconium content, and the intercept of the linear change of the shrinkage rate with zirconium content, a shrinkage rate prediction model for the solidification shrinkage behavior is constructed. When the weight percentage of zirconium in the magnesium alloy is greater than 0.35% and less than or equal to 2.00%, the linear change of the shrinkage rate in the solidification shrinkage behavior is obtained through the shrinkage rate prediction model for the solidification shrinkage behavior, and the shrinkage rate of the magnesium alloy undergoing solidification shrinkage behavior is predicted. The first extreme point of the shrinkage rate variation range is 0.100‰, the second extreme point of the shrinkage rate variation range is 0.780‰, the slope of the linear change of the shrinkage rate with zirconium content is 23.609, and the intercept of the linear change of the shrinkage rate with zirconium content is 0.306‰.
4. The method for predicting the expansion and shrinkage rates during the solidification of Mg-Zr alloys according to claim 3, characterized in that, The linear change in the shrinkage rate during the liquid phase shrinkage behavior is as follows: yls =k lsx +b ls in, yls k is the shrinkage rate of the liquid phase shrinkage behavior. ls Let be the slope of the linear model of shrinkage rate as a function of zirconium content in the liquid phase shrinkage behavior, where x is the zirconium content in the magnesium alloy, and b is the zirconium content. ls The intercept of the model for the linear change of shrinkage rate with zirconium content in the liquid phase shrinkage behavior; The linear change in the shrinkage rate during solidification shrinkage is as follows: yss =k ssx +b ss in, yss k is the shrinkage rate of solidification shrinkage behavior. ss Let x be the slope of the linear model of solidification shrinkage as a function of zirconium content, and b be the zirconium content in the magnesium alloy. ss The intercept of the model for the linear variation of shrinkage rate with zirconium content in solidification shrinkage behavior.