How is the research and development progress of magnesium-based composite castings?

 

Magnesium-based composite castings have made considerable progress in research and development. In some specific areas, there is a trend to replace traditional magnesium alloys, but they cannot be completely replaced at present. The following are the specific situations:

Research and development progress
Performance improvement: By adding various non-metallic materials, such as ceramics or carbon materials, to magnesium or magnesium alloys as reinforcing phases, magnesium-based composite materials have greatly improved strength and modulus while having the lightweight advantages of magnesium alloys. For example, a study has prepared a magnesium-based composite deep-cavity cylindrical casting with a tensile strength of 320-340MPa, a yield strength of 240-260MPa, an elongation of 3%-4%, and a modulus of 68GPa.

Preparation process: New preparation methods and processes are constantly emerging and improving. For example, the method of preparing particle-reinforced magnesium alloy composites by semi-solid vacuum hot pressing, the method of preparing mixed carbon fiber-reinforced magnesium alloy composites, and the method of preparing magnesium-based composite materials reinforced with magnesium borate whiskers can improve the hardness and strength of the magnesium alloy matrix to a certain extent. In addition, there are studies to solve the problems in the preparation process by making specific proportions of raw materials, pre-treating the reinforcement phase, optimizing the melting and casting process parameters, etc. For example, by preheating the reinforcement phase particles, ensuring its bonding with the composite metal liquid and reducing defects such as holes; using low-pressure casting to make the magnesium-based composite material mixed slurry fill the mold evenly, smoothly and completely, and obtain a denser organization.

R&D cooperation: According to reports, the international expert group for cooperative research on high-performance rare earth magnesium alloys and magnesium-based composite materials conducted technical exchanges at Dongqing Company. The specifications of high-performance rare earth magnesium alloys and magnesium-based composite material casting rods produced by Dongqing are the largest in the world, reaching the standards of Japanese products of this model. The experiment achieved the expected results, which shows that certain results have been achieved in international cooperative research and development.

Replacement of traditional magnesium alloys
Advantages make it substitutable in some fields
High-performance demand fields: In aerospace, automotive and other fields with strict requirements on material performance, magnesium-based composite castings can meet the requirements of these fields for the use of materials under harsh and heavy load conditions due to their higher strength, modulus and better wear resistance. Therefore, it is possible to gradually replace traditional magnesium alloys in these fields. For example, in the preparation of aerospace parts and automotive parts, deep-cavity cylindrical castings of magnesium-based composite materials have shown good application prospects.
Special environment application fields: Magnesium-based composite materials have excellent comprehensive properties such as low thermal expansion coefficient, high Young’s modulus and good wear resistance. In some special environments such as high temperature and high wear, they are more advantageous than traditional magnesium alloys, so they have the potential to replace traditional magnesium alloys in these specific environmental application scenarios.

Restrictive factors lead to inability to completely replace
High preparation cost: The preparation process of magnesium-based composite materials is relatively complicated, requiring the addition of special reinforcement phases, and the preparation process requirements are high, resulting in its cost being usually much higher than that of traditional magnesium alloys. This makes traditional magnesium alloys still have great advantages in some cost-sensitive fields, such as some civilian ordinary product fields, because these fields pay more attention to the cost performance of materials.
Difficulty in forming: With the addition of reinforcement phase particles, the viscosity of the composite melt increases significantly, and the convective heat transfer of the melt in the crucible is weakened during the smelting process, resulting in an increase in the non-uniformity of the melt temperature field, which directly affects the formability of complex castings. At the same time, there is a large gap between the thermophysical properties of magnesium alloys and reinforcing phases such as inorganic ceramic particles. Casting defects are easily introduced during the molding process of complex castings, thereby affecting the mechanical properties of complex components of magnesium-based composite materials, which also limits its replacement of traditional magnesium alloys in some complex structural parts.

Technical maturity needs to be improved: Despite progress in research and development, the production process of magnesium-based composite castings is still not mature and stable enough, and large-scale industrial production still faces some technical challenges, such as the uniform dispersion of reinforcing phases in the matrix, while the production technology of traditional magnesium alloys is relatively mature, which also makes it impossible for magnesium-based composite materials to completely replace traditional magnesium alloys at this stage.