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300W,扫描速度900mm/s;优化的时效工艺参数为:时效温度325℃,时效时间4h。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℃/4h时效处理后,合金的抗拉强度达565MPa,屈服强度达520MPa,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。
The ultra-fine structured Ni?Al?WC layer with interlocking bonding was fabricated on austenitic stainless steel by combination of laser clad and friction stir processing (FSP). Laser was initially applied to Ni?Al elemental powder preplaced on the austenitic stainless steel substrate to produce a coating for further processing. The as-received coating was subjected to FSP treatment, processed by a rotary tool rod made of WC?Co alloy, to obtain sample for inspection. Microstructure, phase constitutions, hardness and wear property were investigated by methods of scanning electronic microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX) microanalysis, and X-ray diffraction (XRD), hardness test alongside with dry sliding wear test. The results show that the severe deformation effect exerted on the specimen resulted in an ultra-fine grain layer of about 100μmin thickness and grain size of 1?2μm. Synergy between introduction of WC particles to the deformation layer and deformation strengthening contributes greatly to the increase in hardness and friction resistance. An interlocking bonding between the coating and matrix which significantly improves bonding strength was formed due to the severe deformation effect.
