Microstructure and Mechanical Properties of Mg-6Al-5Zn-xCa(x=4, 5, 6, 7)-5Gd Alloys

作者：Zhang Daidong^*; Shi Xiaobao; Cai Yancen; Fang Daqing; Chai Yuesheng

来源：Rare Metal Materials and Engineering, 2016, 45(4): 1054-1059.

• Mg-6Al-5Zn-xCa-5Gd alloys
• heat treatment
• beta-Mg-25(Al, Zn)(37.5)
• microstructure and mechanical properties

The effects of different high Ca contents and heat treatment on microstructure and mechanical properties of the as-cast Mg-6Al-5Zn-xCa-5Gd alloys were investigated. The results indicate that with the addition of Ca in as-cast condition, the beta-Mg-25(Al, Zn)(37.5) phase which continuously distributes in grain boundary becomes finer. The granular Al2Gd and the block CaZn5 phase gradually dissolve in the matrix more uniformly. Hence the tensile strength and yield strength increase firstly and then decrease, while the elongation decreases all the way. After the solid solution treatment, most of beta-Mg-25(Al, Zn)(37.5) phase is dissolved in the matrix, and the strength and the elongation increase obviously. With the increase of Ca content, much more granular and lump phase distribute in the surface. And the ultimate tensile strength and yield strength increase firstly and then decrease, but little change has happened with the elongation. After solid solution treatment and aging treatment, the age-hardening of alloys reaches the peak at 12 h. Then the hardness tends towards stability after slight lowering, which shows that the alloy has significant thermal stability. Fracture analysis shows that with the increase of calcium and the different heat treatment, fracture mechanism of the alloys transforms from brittle to ductile. With the content of Ca increasing to 6 wt%, dimples can be observed obviously. After the heat treatment, the dimples increase and their sizes are uniform. The Mg-6Al-5Zn-6Ca-5Gd alloy with solid solution treatment at 390 degrees C/8 h and aging treatment at 200 degrees C /12 h gets optimal mechanical properties.

• 出版日期2016-4
• 单位太原科技大学