Effects of processing parameters on microstructure and ultimate tensile strength of thixoformed AM60B magnesium alloy

Abstract

The effects of processing parameters, such as the punch speed, reheating duration and reheating temperature, on microstructure and ultimate tensile strength (UTS) of thixoformed AM60B magnesium alloy have been investigated. The results indicate that low punch speed, short reheating duration or low reheating temperature often produces the defect of cold shuts or shrinkage porosities. On the contrary, gas pores can easily form. In addition, the reheating duration or temperature also has obvious effects on the primary particle size, fraction and morphology. The three parameters can significantly affect the UTS due to their effects on the formation of pores (cold shuts, shrinkage porosities and gas pores). But they can not alter the fracture path during tensile testing and the path is always along the secondarily solidified structures between the primary particles. The effect of pore amount on the UTS is lager than that of the primary particle size, fraction or morphology. In view of their effects on the microstructure compactness and the resultant UTS, the optimized parameters are reheating for 130 minutes at 610 °C and punch speed of 3 m/s.

Effects of reheating temperature and time on microstructure and tensile properties of thixoforged AZ63 magnesium alloy

“…As for the increase of the primary particle size with the reheating temperature, the other one important reason is that the primary particles in the semisolid ingots before forming originally coarsen with rising reheating temperature. 18,21,22 It is just this reason that the primary particles in the alloy formed under 605uC are obviously larger than those in the alloys formed under 590 and 595uC (comparing Fig. 3a-c), although they are separated by the secondarily solidified structures.…”

“…During thixoforging, the secondarily primary a-Mg phase preferentially directly grows up from the surfaces of the primary particles without renucleation. [21][22][23] The eutectic a-Mg phase then also preferentially forms on the secondarily primary a-Mg phase and only the eutectic b phase is left in the finally solidified regions. For Mg-Al alloys, the Al element is a necessary constituent for forming eutectic b phase (Mg 17 Al 12 ).…”

Effect of Microstructures and Mechanical Properties of Large Deformation High Entropy Alloy CoCrCuFeNi in Semi-solid Isothermal Heat Treatment

“…The semi-solid metal process (SSM), as the most promising material-forming process in the 21st century, combined with the advantages of solidification and plastic processing, such as the good flowing ability, low resistance to deformation, and easy formation of complex and high precision parts [9,10] .The key to the SSM process is to obtain a semisolid slurry with a uniform, small non-dendritic structure. The required spherical microstructure can be generated by either a liquid or a solid route.…”

High-Frequency Induction Heating of Al-Si-Cu-Mg aluminum alloy in Thixoforming

“…The process involves two stages, namely, reheating and forming 1 . Reheating the billet in a semisolid state is a particularly crucial stage in thixoforming and is mainly achieved by induction heating to obtain a uniform nondendritic microstructure [2][3][4][5][6][7][8][9] . This inductive heating system is non-contact, clean, precise and rapid in heating 7,8 .…”