(1. 中国铝业郑州研究院 绿色冶金与材料研究所，郑州 450041；
2. 中南大学 材料科学与工程学院，长沙 410083)
摘 要: 对Mg-9Gd-4Y-0.6Zr合金挤压态和挤压T5态在275~350 ℃的高温下时效0~96 h，测试两种状态在时效过程中的硬度变化，并用透射电镜观察析出相的组织演变。结果表明：合金挤压T5态比挤压态在275~350 ℃高温时效中的硬度高，并具有较好的耐热性。合金挤压T5态在275~350 ℃的高温二次时效过程中产生回归现象，二次时效的温度越高，回归现象越明显，形成β1相的速度越快，达到平衡相(β相)所需的时间也越短。β′相向β1相转变所需的相变时间最长；β1相向β相转变所需相变时间最短，组织内会出现β′相、β1相和β相三相共存；因此，β′相向β1相的转变一旦完成，合金的硬度和耐热性急剧地下降。
关键字: Mg-Gd-Y-Zr合金；二次时效；析出相；耐热性
（1. Green Metallurgy and Materials Division, Zhengzhou Research Institute of Chalco, Zhengzhou 450041, China;
2. School of Materials Science and Engineering, Central South University, Changsha 410083, China）
Abstract:The as-extruded and extruded-T5 Mg-9Gd-4Y-0.6Zr alloys were aged in the temperature range of 275−350 ℃ for 0−96 h, the hardness was tested and the microstructure evolution was studied by transmission electron microscope. The results show that the extruded-T5 alloy has higher hardness and better heat resistance than the as-extruded alloy during high temperature ageing. The retrogression phenomenon occurs during the secondary ageing of the extruded-T5 alloy. The higher the secondary ageing temperature is, the more significant the retrogression phenomenon is, the faster the β1 formation is, the shorter the time of transforming to the equilibrium phase β is. The time of β′ phase transforming into β1 phase is the longest during secondary ageing, while that of β1 phase transforming to β phase is the shortest and three phases of β′, β1 and β can co-exist in the aged microstructure. The hardness and heat resistance drop sharply once the β′ phase transforms to β1 phase.
Key words: Mg-Gd-Y-Zr alloy; secondary ageing; precipitate; heat-resistance
