Ti reinforced magnesium matrix composite material with bimodal distribution of reinforcement phases and method for producing same

Abstract

The application belongs to the technical field of metal matrix composite material, and particularly relates to a Ti reinforced phase bimodal distribution magnesium matrix composite material and a preparation method thereof. The preparation method comprises the following steps: mechanical alloying of titanium powder and magnesium matrix powder to obtain mixed powder A; mixing of the mixed powder A and titanium powder to obtain mixed powder B; forming of the mixed powder B to obtain a magnesium matrix composite material; and heat treatment of the magnesium matrix composite material to obtain the Ti reinforced phase bimodal distribution magnesium matrix composite material. The micron / submicron Ti phase dispersedly distributed at the magnesium grain boundary, the nanoscale Ti phase uniformly precipitated in the grain and at the grain boundary after heat treatment, the strength of the magnesium matrix composite material is significantly improved under the action of Orowan strengthening and load strengthening. The application has low material cost, simple preparation process flow, low requirement on equipment, high production efficiency, high product stability, and good industrialization prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of preparation of metal matrix composites, and particularly relates to a Ti-reinforced bimodal distribution magnesium matrix composite and a preparation method thereof. BACKGROUND

[0002] The information disclosed in this Background section is only for the purpose of increasing an understanding of the general background of the application and does not necessarily constitute an admission or a recognition that the information forms part of the prior art that is already known in any country in the world.

[0003] Magnesium alloy has many advantages such as small density, high specific strength, large specific stiffness, easy recycling, and has extremely important application value and prospect in the fields of aerospace, automobile, optical instruments and the like. However, magnesium alloy still has problems such as low absolute strength and elastic modulus, which seriously limit its development and application. In response to the above constraints, it is an effective means to solve the above problems by introducing a reinforcing body to prepare a magnesium matrix composite with higher absolute strength and elastic modulus. Therefore, the research and development of magnesium matrix composite has attracted great attention.

[0004] Compared with ceramic particles, Cu, Ni, Fe and Ti have high strength, excellent plasticity and elastic modulus. However, Cu, Ni and Fe are easy to form brittle intermetallic compounds with Mg, which has an adverse effect on the corrosion resistance of Mg matrix, and are not suitable for the preparation of magnesium matrix composite. Among the many metal materials, Ti is an ideal reinforcing metal material for magnesium matrix composite. The elastic modulus of Ti is almost 2.5 times that of Mg or Mg alloy, reaching 110 GPa, which is conducive to improving the elastic modulus of magnesium matrix composite. Ti is almost insoluble in Mg and does not form intermetallic compounds with Mg, which is an ideal second-phase dispersion strengthening material for Mg. Ti and Mg have similar crystal structures at room temperature, both of which are hexagonal close-packed crystal structures, which is conducive to the formation of coherent interfaces and the improvement of interface bonding strength. Moreover, compared with ceramic particles, Ti is deformable. During plastic deformation, Ti may deform cooperatively with the Mg matrix, which helps to improve the plasticity of magnesium matrix composite.

[0005] The existing public literature reports that Ti particle reinforced magnesium matrix composite is prepared by stirring casting, semi-solid and powder metallurgy process, realizing uniform dispersion of Ti particles in magnesium matrix, but there are the following shortcomings: (1) According to the Orowan dispersion strengthening model, sub-micron and micron Ti particles have no obvious strengthening effect on magnesium matrix; (2) Nano Ti particles are very active, and there is titanium oxide on the surface, which affects the bonding strength in the matrix; (3) Nano Ti particles are difficult to achieve uniform dispersion, and generally distribute along the magnesium grain boundary, which is difficult to achieve ideal strengthening effect. SUMMARY

[0006] In order to solve the problems of the prior art, the purpose of the present application is to provide a magnesium-based composite material with bimodal distribution of Ti reinforcing phase and a preparation method thereof. By mechanical alloying and mechanical mixing, bimodal distribution of Ti phase in the magnesium matrix is obtained, and the strength of the magnesium-based composite material is improved by Orowan strengthening and load bearing strengthening. The process flow of the present application is simple, the equipment requirement is low, the production efficiency is high, the product stability is good, the cost is low, and it has good industrialization prospect.

[0007] The design idea of the present application for improving the strength of the heterogeneous Ti particle reinforced magnesium-based composite material is to:

[0008] The titanium powder and the magnesium-based powder are mixed by mechanical alloying to achieve supersaturation of titanium elements in the magnesium matrix, and then the titanium elements dissolved in the magnesium matrix are precipitated by heat treatment process to obtain nanoscale titanium particles uniformly distributed in the magnesium matrix and well combined with the matrix. The micron-sized titanium particles added by mechanical mixing form a bimodal distribution of titanium particles in the magnesium matrix, which improves the absolute strength of the composite material while ensuring the elastic modulus of the composite material.

[0009] In order to achieve the above purpose, the present application is realized by the following technical scheme:

[0010] In a first aspect, the present application provides a preparation method of a magnesium-based composite material with bimodal distribution of Ti reinforcing phase, comprising the following steps:

[0011] S1, mechanically alloying titanium powder and magnesium-based powder to obtain mixed powder A;

[0012] S2, mixing the mixed powder A with titanium powder to obtain mixed powder B;

[0013] S3, shaping the mixed powder B to obtain a magnesium-based composite material;

[0014] S4, heat treating the magnesium-based composite material to obtain a magnesium-based composite material with bimodal distribution of Ti reinforcing phase.

[0015] Preferably, in step S1, the magnesium-based powder is pure magnesium powder or magnesium alloy powder with an average particle size of 10-2mm.

[0016] Preferably, in step S1, the purity of the titanium powder is greater than 99.5wt.%, and the average particle size is 1-2μm.

[0017] Preferably, in step S1, the mass of the titanium powder is 1-5% of the total mass of the titanium powder and the magnesium-based powder.

[0018] Preferably, in step S1, the mechanical alloying method comprises ball milling, the ball milling ball-to-material ratio is 50-70:1, the ball milling time is 12-20h, and the ball milling rotation speed is 250-350rpm.

[0019] Preferably, in step S2, the purity of the titanium powder is greater than 99.5wt.%, the average particle size is 2-20μm, and the mass of the titanium powder is 5%-20% of the total mass of the titanium powder and the mixed powder A.

[0020] Preferably, in step S3, the forming comprises room temperature press forming or powder extrusion forming.

[0021] Further preferably, the pressure of the room temperature press forming is 1.2-1.4GPa, and the pressure holding time is 5-10min; the extrusion ratio of the powder extrusion forming is 9-11:1, the extrusion temperature is 290-310℃, and the holding time of the extrusion billet is 0.9-1.1h.

[0022] Preferably, in step S4, the temperature of the heat treatment is 300-450℃, and the heat treatment time is 0.5-10h.

[0023] In a second aspect, the present application provides a Ti-reinforced phase bimodal distribution magnesium-based composite material, which is obtained by the preparation method as described in the first aspect.

[0024] The beneficial effects achieved by the one or more technical solutions of the present application are as follows:

[0025] (1) The present application realizes the bimodal distribution of titanium particles in the magnesium matrix based on mechanical alloying and mechanical mixing, effectively improves the absolute strength of the magnesium-based composite material by using the Orowan strengthening and load-bearing strengthening of nanoparticles without increasing the content of titanium phase, has the advantages of low cost, simple material preparation process, high production efficiency, and good product stability.

[0026] (2) The present application realizes the uniform and dispersed distribution of nanoscale titanium particles in the magnesium matrix by mechanical alloying and heat treatment process, improves the thermal stability of the magnesium matrix by using pinning effect to prevent the movement of magnesium matrix grain boundary atoms in the thermal environment, and is conducive to the maintenance of fine-grain strengthening effect, and has good product stability. BRIEF DESCRIPTION OF DRAWINGS

[0027] The drawings accompanying the specification of the present application form a part thereof, serve to provide further understanding of the present application, and together with the description of the exemplary embodiments of the present application and their description serve to explain the present application, and do not constitute an improper limitation of the present application.

[0028] Figure 1 The transmission electron microscope images of the magnesium-based composite material (a) prepared in Example 1 of the present application and the Ti-reinforced phase bimodal distribution magnesium-based composite material (b).

[0029] Figure 2 A schematic diagram of the microstructure of the magnesium matrix composite with bimodal distribution of Ti reinforcing phase in Example 1 of the present application. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below in combination with specific examples and comparative examples.

[0031] Example 1

[0032] In this example, a magnesium matrix composite with bimodal distribution of Ti reinforcing phase and a preparation method thereof are provided, and the preparation method comprises the following steps:

[0033] (1) Mechanical alloying of titanium powder and magnesium-based powder to obtain mixed powder A.

[0034] The magnesium-based powder is AZ91 magnesium alloy powder with an average particle size of 45 μm. The titanium powder has an average particle size of 1 μm and a mass of 4% of the total mass of the titanium powder and the magnesium-based powder. Mechanical alloying is achieved by ball milling at a ball-to-material ratio of 60:1 for 16 h at a rotation speed of 300 rpm.

[0035] (2) Mechanical mixing of mixed powder A and titanium powder to obtain mixed powder B.

[0036] The titanium powder has an average particle size of 2 μm and a mass of 14% of the total mass of the titanium powder and the mixed powder A.

[0037] (3) Forming of powder B by room temperature pressing to obtain a magnesium matrix composite.

[0038] The room temperature pressing pressure is 1.3 GPa, and the pressure holding time is 5 min.

[0039] (4) Obtaining a magnesium matrix composite with bimodal distribution of Ti reinforcing phase by a heat treatment process.

[0040] The heat treatment temperature is 300 °C, and the holding time is 1 h.

[0041] The magnesium matrix composite obtained in step (3) is observed by transmission electron microscopy, and the results are shown in Fig. a. The Ti particles are dispersedly distributed in the magnesium matrix, and no precipitated phase is observed. The magnesium matrix composite with bimodal distribution of Ti reinforcing phase obtained in step (4) is observed by transmission electron microscopy, and the results are shown in Fig. b. A large number of nanoscale Ti precipitated phases are observed to be distributed in the magnesium grains and at the grain boundaries, with an average particle size of about 15 nm. The Ti particles and the nanoscale Ti precipitated phases are uniformly distributed in the magnesium matrix. Figure 1 Figure 1 ​​

[0042] A schematic diagram of the microstructure of the magnesium matrix composite with bimodal distribution of Ti reinforcing phase is shown in Figure 2 The magnesium matrix composite with bimodal distribution of Ti reinforcing phase was obtained by mechanical alloying and powder mixing.

[0043] The hardness of the magnesium matrix composite with bimodal distribution of Ti reinforcing phase was tested, and the material hardness reached 175HV. Therefore, the magnesium matrix composite with bimodal distribution of Ti reinforcing phase has high strength.

[0044] The magnesium matrix composite with bimodal distribution of Ti reinforcing phase was heat treated at a temperature of 450℃ for 10h. The microstructure of the material after heat treatment was observed, and the average grain size of the magnesium matrix was 200nm. Therefore, the magnesium matrix composite with bimodal distribution of Ti reinforcing phase has excellent microstructure thermal stability.

[0045] Comparative Example 1

[0046] The method is basically the same as that of Example 1, except that no titanium powder is added in step (1). The specific steps are as follows:

[0047] (1) The magnesium matrix powder was mechanically alloyed to obtain powder A.

[0048] The magnesium matrix powder was AZ91 magnesium alloy powder with an average particle size of 45μm. Mechanical alloying was carried out by ball milling at a ball-to-material ratio of 60:1 for 16h at a rotation speed of 300rpm.

[0049] (2) A and titanium powder were mechanically mixed to obtain mixed powder B.

[0050] The average particle size of the titanium powder was 2μm, and the mass of the titanium powder was 14% of the total mass of the titanium powder and the mixed powder A.

[0051] (3) The powder B was formed by room temperature pressing to obtain a magnesium matrix composite.

[0052] The room temperature pressing pressure was 1.3GPa, and the holding time was 5min.

[0053] (4) A heterogeneous Ti particle reinforced magnesium matrix composite was obtained by heat treatment process.

[0054] The heat treatment temperature was 300℃, and the holding time was 1h.

[0055] The hardness of the heterogeneous Ti particle reinforced magnesium matrix composite obtained in step (4) was tested, and the material hardness was 135HV.

[0056] Comparative Example 2

[0057] The method is basically the same as that in Example 1, except that in step (1) no titanium powder is added, and in step (2) the mass of the titanium powder is 18% of the total mass of the titanium powder and the mixed powder A. The specific steps are as follows:

[0058] (1) The magnesium-based powder is mechanically alloyed to obtain powder A.

[0059] The magnesium-based powder is AZ91 magnesium alloy powder with an average particle size of 45 μm. Mechanical alloying is performed by ball milling at a ball-to-material ratio of 60:1 for 16 h at a rotation speed of 300 rpm.

[0060] (2) A is mechanically mixed with titanium powder to obtain mixed powder B.

[0061] The titanium powder has an average particle size of 2 μm and a mass of 18% of the total mass of the titanium powder and the mixed powder A.

[0062] (3) Powder B is formed by room temperature pressing to obtain a magnesium-based composite material.

[0063] The room temperature pressing pressure is 1.3 GPa, and the pressure holding time is 5 min.

[0064] (4) A heterogeneous Ti particle reinforced magnesium-based composite material is obtained by a heat treatment process.

[0065] The heat treatment temperature is 300°C, and the holding time is 1 h.

[0066] The hardness of the heterogeneous Ti particle reinforced magnesium-based composite material obtained in step (4) is tested, and the material hardness is 145 HV.

[0067] Example 2

[0068] A Ti reinforced phase bimodal distribution magnesium-based composite material and a preparation method thereof are provided in this example, and the preparation method comprises the following steps:

[0069] (1) Titanium powder is mechanically alloyed with magnesium-based powder to obtain mixed powder A.

[0070] The magnesium-based powder is AZ91 magnesium alloy powder with an average particle size of 2 mm. The titanium powder has an average particle size of 1 μm and a mass of 4% of the total mass of the titanium powder and the magnesium-based powder. Mechanical alloying is performed by ball milling at a ball-to-material ratio of 60:1 for 16 h at a rotation speed of 300 rpm.

[0071] (2) A is mechanically mixed with titanium powder to obtain mixed powder B.

[0072] The titanium powder has an average particle size of 2 μm and a mass of 14% of the total mass of the titanium powder and the mixed powder A.

[0073] (3) Powder B is formed by powder extrusion to obtain a magnesium-based composite material.

[0074] The extrusion ratio of the powder extrusion was 10:1, the extrusion temperature was 300°C, and the holding time of the extrusion blank was 1 h.

[0075] (4) A heat treatment process was used to obtain the Ti-reinforced magnesium-based composite material with bimodal distribution of reinforcing phases.

[0076] The heat treatment temperature was 300°C, and the holding time was 1 h.

[0077] The hardness and compressive mechanical properties of the Ti-reinforced magnesium-based composite material with bimodal distribution of reinforcing phases obtained in step (4) were tested, and the material hardness was 205 HV, and the yield strength was 680 MPa. Therefore, the Ti-reinforced magnesium-based composite material with bimodal distribution of reinforcing phases prepared in this embodiment has high strength.

[0078] Comparative Example 3

[0079] The method was basically the same as that in Example 2, except that the composite material was not subjected to heat treatment in the comparative example, and the specific steps were as follows:

[0080] (1) Titanium powder and magnesium-based powder were mechanically alloyed to obtain mixed powder A.

[0081] The magnesium-based powder was AZ91 magnesium alloy powder with an average particle size of 2 mm. The titanium powder had an average particle size of 1 μm and a mass of 4% of the total mass of the titanium powder and the magnesium-based powder. Mechanical alloying was performed by ball milling at a ball-to-material ratio of 60:1 for 16 h at a ball milling speed of 300 rpm.

[0082] (2) A and titanium powder were mechanically mixed to obtain mixed powder B.

[0083] The titanium powder had an average particle size of 2 μm and a mass of 14% of the total mass of the titanium powder and the mixed powder A.

[0084] (3) Powder extrusion was used to form powder B to obtain a magnesium-based composite material.

[0085] The extrusion ratio of the powder extrusion was 10:1, the extrusion temperature was 300°C, and the holding time of the extrusion blank was 1 h.

[0086] The hardness and compressive mechanical properties of the magnesium-based composite material obtained in step (3) were tested, and the material hardness was 185 HV, and the yield strength was 620 MPa, both of which were lower than those of the Ti-reinforced magnesium-based composite material with bimodal distribution of reinforcing phases prepared in Example 2.

[0087] Example 3

[0088] The present embodiment provides a Ti-reinforced magnesium-based composite material with bimodal distribution of reinforcing phases and a preparation method thereof, and the preparation method comprises the following steps:

[0089] (1) Mechanical alloying of titanium powder and magnesium-based powder to obtain mixed powder A.

[0090] The magnesium-based powder is pure magnesium powder with an average particle size of 10 μm. The titanium powder has an average particle size of 2 μm and a mass of 1% of the total mass of the titanium powder and the magnesium-based powder. Mechanical alloying is performed by ball milling at a ball-to-material ratio of 60:1 for 16 h at a rotation speed of 300 rpm.

[0091] (2) Mechanical mixing of A and titanium powder to obtain mixed powder B.

[0092] The titanium powder has an average particle size of 20 μm and a mass of 20% of the total mass of the titanium powder and the mixed powder A.

[0093] (3) Shaping of powder B by room temperature pressing to obtain a magnesium-based composite material.

[0094] The room temperature pressing is performed at a pressure of 1.3 GPa for 5 min.

[0095] (4) Heat treatment process to obtain a magnesium-based composite material with bimodal distribution of Ti reinforcing phase.

[0096] The heat treatment is performed at a temperature of 300 °C for 1 h.

[0097] Hardness testing of the magnesium-based composite material with bimodal distribution of Ti reinforcing phase obtained in step (4) shows a material hardness of 110 HV.

[0098] Comparative Example 4

[0099] The procedure is essentially the same as in Example 3, except that no titanium powder is added in steps (1) and (2) in the comparative example. The procedure is as follows:

[0100] (1) Mechanical alloying of magnesium-based powder to obtain powder A.

[0101] The magnesium-based powder is pure magnesium powder with an average particle size of 10 μm. Mechanical alloying is performed by ball milling at a ball-to-material ratio of 60:1 for 16 h at a rotation speed of 300 rpm.

[0102] (2) Mechanical mixing of powder A to obtain powder B.

[0103] (3) Shaping of powder B by room temperature pressing to obtain a magnesium-based material.

[0104] The room temperature pressing is performed at a pressure of 1.3 GPa for 5 min.

[0105] (4) Heat treatment process to obtain a magnesium-based material.

[0106] The heat treatment is performed at a temperature of 300 °C for 1 h.

[0107] The magnesium-based material obtained in step (4) is subjected to hardness test, and the material hardness is 70 HV.

[0108] The above examples and comparative examples show that the present application realizes the bimodal distribution of Ti reinforcement in the magnesium matrix by mechanical alloying and mechanical mixing, effectively improves the absolute strength of the magnesium-based composite material without increasing the content of titanium phase by using the Orowan strengthening and load strengthening of nanoparticles, improves the thermal stability of the magnesium matrix by using the pinning effect, and has the potential for large-scale application due to the simple preparation process and high production efficiency.

[0109] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a magnesium-based composite material with a Ti-reinforced phase bimodal distribution, characterized in that, Includes the following steps: S1. Mechanically alloy titanium powder with magnesium-based powder to obtain mixed powder A; S2. Mix the mixed powder A with titanium powder to obtain mixed powder B; S3. The mixed powder B is shaped to obtain a magnesium-based composite material; S4. Heat-treat the magnesium-based composite material to obtain a magnesium-based composite material with a Ti-reinforced phase bimodal distribution; In step S1, the average particle size of the titanium powder is 1-2 μm; In step S1, the mechanical alloying method includes ball milling, with a ball-to-material ratio of 50-70:1, a milling time of 12-20 hours, and a milling speed of 250-350 rpm. In step S1, the purity of the titanium powder is greater than 99.5 wt.%. In step S1, the mass of the titanium powder is 1%-5% of the total mass of the titanium powder and the magnesium-based powder; In step S2, the average particle size of the titanium powder is 2-20 μm; In step S2, the purity of the titanium powder is greater than 99.5 wt.%, and the mass of the titanium powder is 5%-20% of the total mass of the titanium powder and the mixed powder A. In step S4, the heat treatment temperature is 300-450℃ and the heat treatment time is 0.5-10 h.

2. The method for preparing magnesium-based composite material with Ti-reinforced phase dual-modal distribution as described in claim 1, characterized in that, In step S1, the magnesium-based powder is pure magnesium powder or magnesium alloy powder with an average particle size of 10 μm-2 mm.

3. The method for preparing magnesium-based composite material with Ti-reinforced phase dual-modal distribution as described in claim 1, characterized in that, In step S3, the forming process includes room temperature pressing or powder extrusion forming.

4. The method for preparing magnesium-based composite material with Ti-reinforced phase dual-modal distribution as described in claim 3, characterized in that, The room temperature pressing pressure is 1.2-1.4 GPa, and the holding time is 5-10 min; the powder extrusion molding extrusion ratio is 9-11:1, the extrusion temperature is 290-310 ℃, and the extruded billet holding time is 0.9-1.1 h.

5. A magnesium-based composite material with a Ti-reinforced phase bimodal distribution, characterized in that, Obtained by the preparation method according to any one of claims 1-4.

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