摘要
This study focused on modifying heat treatment schemes to enhance the mechanical properties of sand cast Al−2Li−2Cu−0.5Mg−0.2Sc−0.2Zr alloy.Different three-stage solution treatment schemes((460℃,32 h)+(520℃,24 h)+(530/540/550℃,4/12/24/32 h))and aging temperatures(125,175,225℃)were designed for comparison.The microstructure evolutions were analyzed by optical microscopy(OM),scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The results showed that the three-stage solution treatment of(460℃,32 h)+(520℃,24 h)+(530℃,12 h)could dissolve most of the secondary phases.The TEM results illustrated that fineδ'(Al_(3)Li)particles were homogeneously distributed in the matrix after aging at 175℃for 8 h,accompanied by a small amount of lath-shaped S′(Al_(2)CuMg)and plate-like T_(1)(Al_(2)CuLi)phases.The best comprehensive properties of yield strength of 376 MPa,ultimate tensile strength of 458 MPa and elongation of 4.1%were obtained by the optimal heat treatment scheme((460℃,32 h)+(520℃,24 h)+(530℃,12 h)+(175℃,8 h)).
研究不同热处理工艺对砂型铸造Al−2Li−2Cu−0.5Mg−0.2Sc−0.2Zr合金显微组织和力学性能的影响。设计三级固溶处理方案((460℃,32 h)+(520℃,24 h)+(530/540/550℃,4/12/24/32 h))和不同温度(125,175,225℃)时效处理方案用于比较。采用光学显微镜(OM)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)分析显微组织演变过程。结果表明,最佳固溶处理((460℃,32 h)+(520℃,24 h)+(530℃,12 h))可溶解大部分晶界第二相。透射电镜结果表明,经175℃时效8 h后,δ′(Al_(3)Li)颗粒均匀分布于基体中,并伴有少量板条状S′(Al_(2)CuMg)和片状T_(1)(Al_(2)CuLi)相。采用最佳热处理方案((460℃,32 h)+(520℃,24 h)+(530℃,12 h)+(175℃,8 h))可获得屈服强度为376 MPa、极限抗拉强度为458 MPa和伸长率为4.1%的最佳综合性能。
基金
the National Natural Science Foundation of China(Nos.51871148,51821001)
the United Fund of National Department of Education and Equipment Development,China(No.6141A02033245).
