Mg-Y-Sm-Zn-Zr合金的原位合金化成形工艺研究

In-situ Alloying Forming Process of Mg-Y-Sm-Zn-Zr Alloy

摘要:

原位合金化通过成分设计将现有商业粉进行混合配比作为粉末原料进行选区激光熔化（SLM）制造合金零件，该技术有望解决预合金粉末制备难的问题。本研究以Mg、Y、Sm、Zn、Zr单质粉末为原材料，采用SLM原位合金化方法制备了Mg-3.4Y-3.6Sm-2.6Zn-0.8Zr多组元稀土镁合金熔道和块体样品。对不同工艺参数下样品的成形性、相对致密度、表面形貌、微观组织和显微硬度进行了研究，并与预合金试样进行了对比。结果表明，单道次熔道在激光功率80 W时可获得稳定光滑熔道，熔池为传导模式。块体样品在激光功率为80 W、扫描速度300 mm/s时相对致密度最大为98.71%，孔隙和未熔颗粒最少，显微硬度为98.97 HV。原位合金化样品的物相由Mg基体、Y-Zr-O稀土氧化物和共晶相(Mg,Zn)₃(Y,Sm)组成，微观组织为细小的等轴晶。

Abstract:

In-situ alloying employs compositional design to mix commercially available powders in specific ratios as feedstock for fabricating alloy components by selective laser melting (SLM), potentially addressing challenges in preparation of pre-alloyed powder. Melt-track and bulk samples of multi-component rare-earth Mg-3.4Y-3.6Sm-2.6Zn-0.8Zr magnesium alloy were fabricated by SLM in-situ alloying method using Mg, Y, Sm, Zn, and Zr commercial powders as raw materials. The formability, relative density, surface morphology, microstructure and microhardness of the samples under different process parameters were investigated and compared with those of the pre-alloyed powder formed samples. The results show that single melt-track can obtain a stable and smooth melt-track at a laser power of 80 W, and the melt pool is in conduction mode. The bulk sample has the maximum relative density of 98.71% at a laser power of 80 W, and a scanning speed of 300 mm/s, with the fewest pores and unmelted particles and a microhardness of 98.97 HV. The phase composition of the in-situ alloyed samples is composed of Mg matrix, Y-Zr-O rare-earth oxides, and eutectic phase (Mg,Zn)₃(Y,Sm), and the microstructures are mostly fine equiaxed grains.