Abstract
A distinctive solutionizing process parameter was developed and performed to significantly enhance strength and ductility of aged AZ80 Mg alloy. The microstructure-processing-properties relationship was studied to help elucidate the mechanism. Microstructure and mechanical properties were studied by using optical microscopy, Field Emission Scanning Electron Microscopy, Transmission Electron Microscopy, X-ray diffraction, hardness and tensile testing. The results show that the solutionization at 380°C/10h followed by 420°C/10h promoted significant dissolution of eutectic Mg17Al12 and intermetallic phases. After standard aging at 200°C/10h, the formation of high-density precipitates Mg17Al12 with more spheroidization precipitates and lesser discontinuous precipitates morphology, which was not observed in conventional heat treatment for aged AZ80 Mg alloy. Fine precipitates Mg17Al12 resulted in a significant increase in ultimate tensile strength (50.3%), yield strength (35%), elongation (106%) and hardness (40%) compared to conventional heat treated cast AZ80 Mg alloy. These properties are comparable to the commonly used aerospace grade cast aluminium alloy A356.
Highlights
In today’s market, demand for cast magnesium (Mg) alloys is considered one of the largest and fastest-growing due to their wide usage and application
Homogenization treatment helps to increase the uniformity of the material by eliminating composition segregation, non-equilibrium phases and stresses induced during casting solidification
Studies showed that homogenization treatment can effectively improve microstructure uniformity and distribution of the Mg17Al12 phase, as well as enhance mechanical properties of magnesium alloys [26,27]
Summary
In today’s market, demand for cast magnesium (Mg) alloys is considered one of the largest and fastest-growing due to their wide usage and application. Researchers have been trying to enhance the strengthening effect through micro-alloying elements such as Lithium [6], Yttrium [7], Neodymium [8], and Cerium [9] etc Even though those processes can strengthen the properties of the material with good results, their production costs are comparatively higher and cycle time is longer. This has driven efforts to achieve strength enhancement through various heat treatment processes in order to expand its applications. Zhang et al [15] studied heat treatment effects on the mechanical properties of cast AZ80 Mg alloy and achieved a tensile strength of 196-197 MPa and yield strength of 126-129 MPa, but ductility (3.66-4.42%) is still relatively low after aging. Several studies have been devoted to the development of better mechanical performance in as-cast AZ80 with different solutionizing times to enhance the dissolu-
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