Many components of modern automobiles are made of magnesium alloys cast in molds. For automotive applications, the vast majority of magnesium alloy castings are manufactured from Mg-Al base alloys or Mg-Al-Zn base alloys. At room temperature, these alloys have outstanding castability and mechanical qualities, and they are corrosion resistant. The low creep resistance of commercial magnesium alloys including aluminum and a tiny amount of manganese or zinc beyond 120°C, on the other hand, limits their use in high-temperature applications.
A new creep resistance alloy containing strontium (AJ alloys) has been discovered, which exhibits excellent creep performance and tensile strength at temperatures as high as 175 degrees Celsius. These alloys are widely utilized in the automotive industry because of their high creep resistance and great castability characteristics. BMW, for example, used it in the production of its
magnesium & aluminum die casting composite engine block.
High-pressure die casting is the primary method of producing magnesium alloy components for use in the automobile industry, as well as for a wide range of other uses and industries. The mechanical qualities of a die cast product are primarily influenced by the temperature of the die, the velocity of the metal at the gate, and the amount of casting pressure applied to it. The temperature of the die, the filling of the die by the molten metal, the geometrical complexity of the parts, and the cooling rate associated with the die casting process all contribute to the formation of a complex set of potential defects in the finished components. Die casting is a complex process that results in a complex set of potential defects in the finished components. But at this time, it is difficult to determine the relative importance of the various die casting process parameters in terms of the quality of the finished goods.
The work of Tomasz Rzychon and colleagues was motivated by the desire to gain better understanding. The microstructure and mechanical properties of a typical magnesium alloy were investigated by a Polish research team who looked at the effects of hot-chamber die casting conditions on the alloy. During the die casting process, they took into account piston speed, pressure, die temperature, and casting temperature. The porosity of the pressure die cast alloy products has an impact on the mechanical qualities of the alloy products. According to the findings of the study, the applied pressure and the velocity of the plunger, which is a critical component of the shot sleeve, have the greatest impact on gas porosity during the die casting process.
In die castings, a high level of consolidation pressure minimizes the amount of gas porosity present. In the experiment, the following relationship was observed between plunger velocity and area fraction of pores: An increase in the molten metal velocity at the gate induces an increase in the area fraction of pores. The pores in samples that were cast with a lower plunger velocity are smaller in size than the pores in samples that were cast with a greater plunger velocity. Besides that, a low plunger velocity increases the thickness of the skin, which is the porosity-free surface layer of the die cast magnesium alloy, which in turn increases the tensile strength of the die cast magnesium alloy further.
