Microstructure evolution and mechanical properties of rheo-squeeze casting AZ91-Ca alloy during heat treatment

• Published in: China foundry Vol. 14; no. 6; pp. 485 - 491
• Main Authors: Zhang, Yang, Li, Xiao-ping, Sun, Shun-ping, Lu, Ya-lin, Wu, Guo-hua
• Format: Journal Article
• Language: English
• Published: Singapore Springer Singapore 01.11.2017; Foundry Journal Agency; School of Materials Engineering, Jiangsu University of Technology, Changzhou 213001, China%National Engineering Research Center of Light Alloy Net Forming, Shanghai Jiao Tong University, Shanghai 200240, China
• Subjects: Alloys; Casting (Metal); Engineering; Hardness (Materials); heat treatment; Machines; Magnesium alloys; Manufacturing; Materials Engineering; Mechanical properties; Metallic Materials; Metals (Materials); microstructure; Precipitation (Meteorology); Processes; Research & Development; semisolid processing; Specialty metals industry; A; magnesium alloys; microstructure; semisolid processing; heat treatment; mechanical properties; TG146.22
• ISSN: 1672-6421; 2365-9459; 1672-6421
• DOI: 10.1007/s41230-017-7025-y

The rheo-squeeze casting（RSC）process is a newly-developed casting process for high-performance components.In order to further improve the mechanical properties of magnesium alloys,AZ91-2wt.%Ca（AZX912）alloy was prepared by the RSC process and then subjected to heat treatment.The microstructure evolution and mechanical properties of AZX912 alloy during heat treatment were investigated.It was found that during solid solution treatment at 410°C,β-Mg_（17）Al_（12） phase with low melting point dissolves intoα-Mg matrix,while the connected network-like Al_2Ca phase with high melting point tends to separate gradually,and the tips of Al_2Ca phase is partially spheroidized.With the increase of solid solution time,the yield strength（YS）of AZX912 alloy decreases gradually while the ultimate tensile strength（UTS）and elongation to failure（E_f）increase continuously.Isothermal ageing at 225°C promotes the precipitation ofβ-Mg_（17）Al_（12） phase in the matrix of AZX912 alloy.The hardness reaches the peak after ageing for 96 h and the increase in hardness is about 24.8%.The precipitation ofβ-Mg_（17）Al_（12） phase during ageing treatment is beneficial to YS but harmful to E_f.The mechanism of microstructure evolution during heat treatment and its effect on mechanical properties are discussed.