摘要
实验合金中 Bi的加入量为 0 .5%～ 2 % ,合金在 SF61 % /CO2 混合气体保护下熔炼 ,通入氩气精炼后在预热至 2 50°C的金属型中浇铸成 2 30 mm× 40 mm× 2 0 mm的板状试样 ,浇铸温度 72 0°C.将铸态试样经过固溶处理 (42 0°C,1 2 h)后 ,在 2 0 0°C进行时效 .实验结果表明 ,Bi的加入延长了合金的时效进程 ,有效地抑制了时效组织中非连续析出相的形成 ,促进了连续沉淀相的析出 .电子束微区分析 (EDAX)和透射电镜 (TEM)研究表明 ,Bi的加入使 AZ91合金中形成了组成较复杂的连续析出相 Mg17(Al,Bi) 12 ,该析出相与基体之间具有复杂的半共格位向关系 ,提高了强化相的热稳定性 ,从而有助于合金高温力学性能的改善 .
The bismuth additive contents cover a range of 0.5%~2%. A mixture of CO 2/1% SF 6 is used as a protective gas during melting process. The melt is homogenized with argon bubbling before pouring. The test sample plates (230 mm×40 mm×20 mm) are cast at the pouring temperature of 720 °C in a permanent mold preheating to about 250 °C. All the specimens are heated at 420 °C for 12 h followed by quenching, then aged at 200 °C for different times. The results show that the bismuth addition to AZ91 retards the aging process, suppresses the discontinuous precipitation and accelerates the formation of continuous precipitates. EDAX and TEM study indicates that the continuous precipitate in the Bi bearing magnesium alloys has a stoichiometric composition of Mg 17 (Al, Bi) 12 , which has semicoherent orientation relationship with matrix and increases the thermal stability of the precipitates. Accordingly, the heat resistance of magnesium alloy at elevated temperature could be increased by addition of bismuth.
出处
《上海交通大学学报》
EI
CAS
CSCD
北大核心
2001年第3期451-456,共6页
Journal of Shanghai Jiaotong University
