采用激光粉末床熔融(laser powder bed fusion, LPBF)技术成形的Al-Mg-Sc-Zr合金不易开裂、力学性能好,但Sc价格昂贵,因此寻找能替代Sc的元素十分必要。本文以气雾化粉末为原料,采用LPBF技术制备Al-Mg-Sc-Er-Zr合金。通过流体静力天平测量密度和使用金相显微镜观察缺陷,以优化激光工艺参数;采用维氏硬度计测量硬度和使用万能力学试验机进行拉伸实验,以优化时效工艺参数;采用扫描电镜、透射电镜对合金组织进行表征并研究其强化机理。结果表明:优化的LPBF工艺参数为:激光功率300 W,扫描速度900 mm/s;优化的时效工艺参数为:时效温度325 ℃,时效时间4 h。LPBF制备的Al-Mg-Sc-Er-Zr合金呈典型双峰晶粒结构,熔池边界为细小等轴晶,熔池内为粗大柱状晶。经325 ℃/4 h时效处理后,合金的抗拉强度达565 MPa,屈服强度达520 MPa,伸长率为14.5%,硬度(HV)由时效前的118提升至163。时效处理后形成的Mg2Si粒子和纳米Al3(Sc,Zr)粒子能够协同钉扎晶界,提高合金强度。
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