Weldable Al-Ni alloy and preparation method thereof

Abstract

The invention discloses a weldable Al-Ni alloy and a preparation method of the weldable Al-Ni alloy. The weldable Al-Ni alloy comprises nanoscale Ni, Al, Si, nano TiO2 particles and Cr. The preparation method comprises the following steps: after an aluminum ingot is completely molten, adding nanoscale pure nickel powder until the nickel powder is completely molten; silicon powder is mixed, and after refining and degassing, the mixture is cast into an open type small-sized temperature-volume furnace; nano titanium dioxide particles and metal chromium are synchronously added in the gradient cooling process; and after the cooling operation is completed, demolding, crushing and ball-milling powder preparation are performed to obtain a weldable Al-Ni alloy product. In order to solve the problem that an existing nickel-based alloy is prone to generating intergranular cracks during welding, the eutectic reaction characteristic of nickel and aluminum is combined, lattice structure Al3Ni with very high stability is formed, nano TiO2 particles and chromium are used for reinforcing and refining, the plasticity and strength of the alloy are improved through the grain refining effect, and the alloy has the good mechanical property. And therefore, the welding seam repairing capability is better during welding.

Description

Technical Field

[0001] The invention relates to an alloy and a method, and in particular to a weldable Al-Ni alloy and a preparation method thereof. Background Art

[0002] Nickel and nickel-based alloys have special physical, mechanical and corrosion resistance properties and are widely used in high temperature and corrosive environments. However, they have high sensitivity to welding hot cracks during welding and are prone to forming coarse columnar crystals, especially polygonal intergranular cracks at welds, which greatly reduces the performance of the alloy. For intergranular cracks, there is no plastic deformation or the plastic deformation is very small. It is generally believed that when the molten metal solidifies, low-melting-point substances segregate on the grain boundaries, causing part of the liquid to remain at a lower temperature, which causes cracking as the deformation increases. How to reduce the generation of intergranular cracks is one of the key ways to improve the welding performance of nickel-based alloys.

[0003] Aluminum is the third largest nonferrous metal in the world in terms of its reserves in the earth's crust. Its lattice constant (20°C) is 4.0494×10 -10 m, relative density 2.699g / cm 3 , about 1 / 3 of iron or copper, face-centered cubic structure, melting point 660℃, boiling point 2327℃, good plasticity and processing ability. Aluminum has good electrical conductivity and thermal conductivity, second only to silver and copper. It also has good radiation resistance, corrosion resistance and welding performance.

[0004] It is generally known that nickel-aluminum nickel-based alloys have excellent corrosion resistance and high-temperature stability that cannot be replaced by general alloys, and are often used in the automotive, aerospace and other industries. At present, there are few studies on the welding performance of metal nickel-aluminum alloys. It is known that adding nickel elements to pure aluminum ingots can play a certain role in refining grains. Therefore, how to optimize nickel-aluminum nickel-based alloys to make them have excellent welding performance is one of the problems that need to be solved urgently. Summary of the invention

[0005] In order to solve the deficiencies of the above-mentioned technology, the present invention provides a weldable Al-Ni alloy and a preparation method thereof.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a weldable Al-Ni alloy, comprising the following components in parts by weight:

[0007] Nano-grade Ni: 15-20 parts;

[0008] A1: 40-50 parts;

[0009] Si: 5-10 parts;

[0010] Nano-TiO2 particles: 1-3 parts;

[0011] Cr: 1-3 parts.

[0012] A method for preparing a weldable Al-Ni alloy comprises the following steps:

[0013] S1. Hot melting of aluminum ingots: Sprinkle the aluminum ingots with a covering agent and keep them warm at 800°C to melt the aluminum ingots;

[0014] S2. Al-Ni eutectic reaction: After the aluminum ingot is completely melted, add nano-grade pure nickel powder and heat to 1500°C until the nickel powder is completely melted, stir thoroughly and introduce argon gas for degassing;

[0015] S3, metal silicon blending: after nickel powder and aluminum liquid are fully mixed, add silicon powder, continue stirring and introduce argon gas for degassing;

[0016] S4, refining and degassing: press the refining agent into the alloy liquid, refining and degassing, fully stir and slag, let it stand for 10-15 minutes, and repeat once;

[0017] S5. Alloy transfer: The refined alloy products are cast into open small-sized temperature-capacity furnaces, and the furnace walls are pre-coated with a release agent;

[0018] S6, gradient cooling: cooling from 100°C to 900°C, adding nano-titanium dioxide particles and metallic chromium simultaneously during the gradient cooling process; after the cooling operation is completed, the alloy product is in a solidified state;

[0019] S7, alloy product demoulding: demoulding the alloy in the small holding furnace;

[0020] S8, crushing: placing the demoulded alloy product into an alloy crusher for crushing to obtain a primary alloy product;

[0021] S9. Ball milling: After drying the primary alloy product at 200°C, send it into a ball mill for ball milling to obtain a weldable Al-Ni alloy product.

[0022] Preferably, the Al content in the aluminum ingot is above 98%.

[0023] Preferably, the covering agent is used to prevent oxidation and is composed of potassium chloride and sodium chloride in a mass ratio of 1:1.

[0024] Preferably, hexachloroethane is used as the refining agent, and the amount of the refining agent added is 0.7%-0.8% of the total weight of the alloy.

[0025] Preferably, during the gradient cooling process, the temperature is kept at 50°C for 1 hour after each cooling, and equal amounts of nano-titanium dioxide particles and metallic chromium are added in batches, that is, equal amounts of nano-titanium dioxide particles and metallic chromium are added each time according to the number of cooling times. The nano-titanium dioxide particles and metallic chromium play a role in the process of Al-Ni alloy transforming from liquid to solid.

[0026] Preferably, the open small temperature-capacity furnace is preheated to 1400° C. for transferring the alloy product.

[0027] Preferably, during the ball milling process, argon gas is introduced for protection.

[0028] The invention discloses a weldable Al-Ni alloy and a preparation method thereof. Aiming at the problem that the existing nickel-based alloy is prone to generate intergranular cracks during welding, the eutectic reaction characteristics of nickel and aluminum are combined to form a lattice structure Al3Ni with high stability. In addition, nano-TiO2 particles and chromium are used for strengthening and refining, so as to improve the plasticity and strength of the alloy by refining the grains, thereby being able to show better weld repair ability during welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a flow chart of the preparation method. DETAILED DESCRIPTION

[0030] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0031] Embodiment 1

[0032] This embodiment discloses a weldable Al-Ni alloy, comprising the following components in parts by weight:

[0033] Nano-grade Ni: 15 parts;

[0034] A1: 45 parts;

[0035] Si: 5 parts;

[0036] Nano TiO2 particles: 3 parts;

[0037] Cr:1 part.

[0038] The Al-Ni alloy product is prepared by the following method, and each material component is prepared according to the above weight parts; the preparation steps are as follows:

[0039] S1. Hot melting of aluminum ingots: Sprinkle the aluminum ingots with a covering agent and keep them warm at 800°C to melt the aluminum ingots;

[0040] S2. Al-Ni eutectic reaction: After the aluminum ingot is completely melted, add nano-grade pure nickel powder and heat to 1500°C until the nickel powder is completely melted, stir thoroughly and introduce argon gas for degassing;

[0041] S3, metal silicon blending: after nickel powder and aluminum liquid are fully mixed, add silicon powder, continue stirring and introduce argon gas for degassing;

[0042] S4, refining and degassing: press the refining agent into the alloy liquid, refining and degassing, fully stir and slag, let it stand for 10-15 minutes, and repeat once;

[0043] S5. Alloy transfer: The refined alloy products are cast into open small-sized temperature-capacity furnaces, and the furnace walls are pre-coated with a release agent;

[0044] S6, gradient cooling: cooling from 100°C to 900°C, adding nano-titanium dioxide particles and metallic chromium simultaneously during the gradient cooling process; after the cooling operation is completed, the alloy product is in a solidified state;

[0045] S7, alloy product demoulding: demoulding the alloy in the small holding furnace;

[0046] S8, crushing: placing the demoulded alloy product into an alloy crusher for crushing to obtain a primary alloy product;

[0047] S9. Ball milling: After drying the primary alloy product at 200°C, send it into a ball mill for ball milling to obtain a weldable Al-Ni alloy product.

[0048] The Al content in the aluminum ingot must be above 98% to minimize impurities. The covering agent is used to prevent oxidation and is composed of potassium chloride and sodium chloride in a mass ratio of 1:1. Hexachloroethane is used as a refining agent, and the amount of the refining agent added is 0.7%-0.8% of the total weight of the alloy.

[0049] During the gradient cooling process, the temperature is kept at 50°C for 1 hour after each cooling, and equal amounts of nano-titanium dioxide particles and metallic chromium are added in batches, that is, equal amounts of nano-titanium dioxide particles and metallic chromium are added each time according to the number of cooling times, so that the refinement process can be effectively completed.

[0050] Furthermore, nickel is a transition element with low solubility in aluminum. Therefore, when pure nickel powder is added to hot-melt aluminum liquid, it is easy to saturate and precipitate Ni-rich phase particles in the aluminum matrix. The aluminum liquid is high-purity aluminum with an aluminum content of more than 98%, which reacts with Ni eutectic to form Al3Ni, improving the alloy performance. Al3Ni has a highly stable lattice structure with a lattice constant of 4.104×10 -10 m, which can be coherent with the aluminum matrix, thus hindering the formation and growth of grains, refining the grains and strengthening the alloy.

[0051] Furthermore, since the main impurity in aluminum ingots is metallic Fe, the excessive addition of Ni can form precipitation phases such as Al9FeNi with Fe element. As a nickel-rich phase, the precipitation phase has the characteristics of good dispersibility, thermal stability, distribution and morphology, which improves the mechanical properties of the alloy.

[0052] The addition of silicon can reduce the grain size of nickel-based alloys, increase the grain boundary area, form a finer and more uniform microstructure, and improve the fatigue resistance and wear resistance of the alloy. At the same time, at high temperatures, the solid solubility of nickel in silicon is very large, and the addition of silicon can also form a eutectic alloy with the nickel that has not reacted with aluminum.

[0053] Further, the cooling rate is faster under non-equilibrium solidification conditions after nickel and aluminum are mixed, and, because the alloy structure has less alloying element content in the central nucleation zone when crystallizing, and the more outward solute concentration is higher, the alloying element content at the grain boundary is the highest, resulting in component segregation. Therefore, the present invention is continuously cooled in a gradient temperature mode to avoid too fast solidification rate, and, in each gradient cooling cycle, nano titanium dioxide particles and metallic chromium are added to achieve the refinement of the alloy structure. Specifically, the addition of chromium element can refine the solidification structure of Al-Ni alloy, and can also increase the hardness of the alloy. After nano-TiO2 is added to the alloy, it exists in the form of Ti2O3, which can make the precipitated phase segregated along the grain boundary be in the form of small pieces and small short rods in the weld structure, thereby effectively refining the solidification structure of Al-Ni alloy.

[0054] Therefore, for the weldable Al-Ni alloy and its preparation method disclosed in this embodiment, by optimizing the ratio design of nickel and aluminum alloy, Al3Ni is formed by eutectic reaction of Al and Ni, which hinders the formation of grains. In addition, the addition of silicon and chromium can improve the fatigue resistance of the alloy while also improving the hardness, which is the basis for the welding performance of the alloy; further, chromium and nano-titanium dioxide particles can play a role in further refinement, and the refinement of the alloy structure makes the element distribution uniform, so that the number of precipitated phases increases, the size decreases, and the phases are dispersed in the alloy, which is the result of the combined effects of solid solution strengthening, fine grain strengthening and lattice distortion, which greatly improves the welding performance of the alloy and avoids the generation of polygonal intergranular cracks.

[0055] Embodiment 2

[0056] This embodiment discloses a weldable Al-Ni alloy, comprising the following components in parts by weight:

[0057] Nano-grade Ni: 20 parts;

[0058] A1: 40 parts;

[0059] Si: 7.5 parts;

[0060] Nano TiO2 particles: 1 part;

[0061] Cr: 3 parts.

[0062] The material components are prepared according to the weight proportions of this embodiment, and a weldable Al-Ni alloy is prepared by the same method as in Embodiment 1 (except for the weight proportions of the material components being different, the rest are the same).

[0063] Embodiment 3

[0064] This embodiment discloses a weldable Al-Ni alloy, comprising the following components in parts by weight:

[0065] Nano-grade Ni: 17.5 parts;

[0066] A1: 42.5 parts;

[0067] Si: 5 parts;

[0068] Nano TiO2 particles: 2 parts;

[0069] Cr:2 parts.

[0070] The material components were prepared according to the weight proportions of the present embodiment, and a weldable Al-Ni alloy was prepared by the same method as in the first embodiment (except for the weight proportions of the material components being different, the rest being the same).

[0071] In summary, the present invention improves the plasticity and strength of the alloy by refining the grains, so that the stress of the alloy is more evenly distributed when used for welding, and the impact resistance and fatigue resistance are improved. Fine grains can reduce the grain boundary area and reduce the generation of intergranular cracks, thereby improving the welding performance of the alloy.

[0072] The above implementation modes are not limitations of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the scope of the technical solution of the present invention also belong to the protection scope of the present invention.

Claims

1. A weldable Al-Ni alloy, characterized in that: The composition comprises the following components in parts by weight: Nano-grade Ni: 15-20 parts; A1: 40-50 parts; Si: 5-10 parts; Nano-TiO2 particles: 1-3 parts; Cr: 1-3 parts.

2. The method for preparing a weldable Al-Ni alloy according to claim 1, characterized in that: The preparation method comprises the following steps: S1. Hot melting of aluminum ingots: Sprinkle the aluminum ingots with a covering agent and keep them warm at 800°C to melt the aluminum ingots; S2. Al-Ni eutectic reaction: After the aluminum ingot is completely melted, add nano-grade pure nickel powder and raise the temperature to 1500°C until the nickel powder is completely melted, stir thoroughly and introduce argon gas for degassing; S3, metal silicon blending: after nickel powder and aluminum liquid are fully mixed, add silicon powder, continue stirring and introduce argon gas for degassing; S4, refining and degassing: press the refining agent into the alloy liquid, refining and degassing, fully stir and slag, let it stand for 10-15 minutes, and repeat once; S5. Alloy transfer: The refined alloy products are cast into open small-sized temperature-capacity furnaces, and the furnace walls are pre-coated with a release agent; S6, gradient cooling: cooling from 100°C to 900°C, adding nano-titanium dioxide particles and metallic chromium simultaneously during the gradient cooling process; after the cooling operation is completed, the alloy product is in a solidified state; S7, alloy product demoulding: demoulding the alloy in the small holding furnace; S8, crushing: placing the demoulded alloy product into an alloy crusher for crushing to obtain a primary alloy product; S9. Ball milling: After drying the primary alloy product at 200°C, send it into a ball mill for ball milling to obtain a weldable Al-Ni alloy product.

3. The method for preparing a weldable Al-Ni alloy according to claim 2, characterized in that: The Al content in the aluminum ingot is above 98%.

4. The method for preparing a weldable Al-Ni alloy according to claim 3, characterized in that: The covering agent is used to prevent oxidation and is composed of potassium chloride and sodium chloride in a mass ratio of 1:

1.

5. The method for preparing a weldable Al-Ni alloy according to claim 4, characterized in that: Hexachloroethane is used as a refining agent, and the amount of the refining agent added is 0.7%-0.8% of the total weight of the alloy.

6. The method for preparing a weldable Al-Ni alloy according to claim 2, characterized in that: During the gradient cooling process, the temperature is kept at 50°C for 1 hour after each cooling, and equal amounts of nano-titanium dioxide particles and metallic chromium are added in batches, that is, equal amounts of nano-titanium dioxide particles and metallic chromium are added each time according to the number of cooling times. The nano-titanium dioxide particles and metallic chromium play a role in the process of Al-Ni alloy transforming from liquid to solid.

7. The method for preparing a weldable Al-Ni alloy according to claim 6, characterized in that: The open small temperature-capacity furnace is preheated to 1400°C for the transfer of alloy products.

8. The method for preparing a weldable Al-Ni alloy according to claim 7, characterized in that: During the ball milling process, argon gas was introduced for protection.

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