铸态Al-Mg-Sc-Zr合金退火过程中的硬化行为

来源期刊：金属学报2011年第3期

论文作者：杜刚 杨文 闫德胜 戎利建

文章页码：311 - 316

关键词：Al-Mg-Sc-Zr合金； 退火； 沉淀强化； 显微组织

Key words：Al-Mg-Sc-Zr alloy； annealing； precipitation strengthening； microstructure

摘    要：采用透射电镜、电子探针、拉伸和硬度测试等方法对铸态Al-6Mg-0.2Sc-0.15Zr(质量分数,%)合金在等温退火过程中的硬化行为进行了研究.结果表明,退火过程中Mg分布的变化对合金强度影响不大,细小、弥散的Al₃(Sc,Zr)沉淀相的析出产生了显著的沉淀强化作用.合金在300℃下退火,Al₃(Sc,Zr)沉淀相粗化速率较慢,经过24 h处理后其直径为5 nm,合金屈服强度相对退火前提高约90 MPa;随着退火温度的升高,Al₃(Sc,Zr)相在退火过程中发生不同程度的粗化.450℃/24 h处理后沉淀相直径增大至约30 nm,Al₃(Sc,Zr)相引起的沉淀强化作用下降至30 MPa.铸态Al-6Mg-0.2Sc-0.15Zr合金经过300℃/3 h退火处理后可获得最大的沉淀强化效果.

Abstract: Addition of minor Sc and Zr to the Al-Mg alloys can effectively improve the recrystallization temperature and strength of the alloys due to the formation of L1₂ structured Al₃(Sc, Zr) precipitates.To optimize the mechanical properties of the Al-Mg-Sc-Zr alloys,it is important to understand the precipitation behavior of the Al₃(Sc,Zr) precipitates and the corresponding strengthening effect during the annealing of Al-Mg-Sc-Zr alloys.In this work,isothermal annealing at the temperatures between 250 and 450℃ was conducted to study the precipitation behavior of Al₃(Sc,Zr) particles in the as-cast Al-6Mg-0.2Sc-0.15Zr alloy (mass fraction,%).The results show that dramatic precipitation hardening occurred with the formation of the coherent Al₃(Sc,Zr) precipitates during the annealing.Precipitation process of the Al₃(Sc,Zr) accelerates with the increase of the annealing temperature.After the sample was annealed at 300℃ for 24 h,the Al₃(Sc,Zr) particles were in a size of 5 nm and the yield strength of the as-cast alloy can be increased by 90 MPa.Severe coarsening of Al₃(Sc,Zr) occurred when the annealing temperature is above 400℃.After annealed at 450℃ for 24 h,average particle size of Al₃(Sc,Zr) particles was found increase to 30 nm,with the corresponding precipitation strengthening effect to be about 30 MPa.