热压层合镁锂合金片材制备与组织性能研究

Research on Preparation,Microstructures and Mechanical Properties of Hot-Pressed Laminated Mg-Li Alloy Sheets

采用自行设计制备的LAY821合金,通过挤压和轧制工艺获得热压层合增材制造用LAY821合金片材,并对挤压和轧制变形方式下合金的显微组织和力学性能进行研究,为拓展Mg-Li合金在增材制造领域的应用,提供一定的理论与技术支持。分别用金相显微镜、扫描电镜观察合金的微观形貌,使用能谱仪检测相的成分,X射线衍射仪(XRD)分析合金的相组成,通过拉伸试验测试合金的力学性能。结果表明,LAY821合金主要由α-Mg、β-Li相与分布于晶界和α-Mg相中的Al_(2)Y颗粒构成。经过挤压、轧制和中间退火处理后,合金形成均匀的双相等轴晶结构,平均粒径由11.6μm减小至7.0μm。Al_(2)Y颗粒呈弥散分布,平均粒径由2.2μm减小至1.0μm,XRD检测结果未发现任何新相。合金的极限抗拉强度最高达到290.26 MPa,硬度提高到54.74HV,伸长率达30%以上。力学性能的改善得益于细化的等轴晶结构和Al_(2)Y颗粒的弥散强化作用。LAY821合金片材设计用于热压层合增材制造,制备过程中组织结构可控,其力学性能未产生明显的各向异性。

The LAY821 alloy self-designed is to used to prepare LAY821 alloy sheets for hot-pressing laminated additive manufacturing via extrusion and rolling processes.The microstructures and mechanical properties of the alloy are investigated to provide theoretical and technical foundations for expanding the application of Mg-Li alloy in additive manufacturing.The microstructures are observed by metallurgical microscope and SEM.The phase compositions of the alloy are analyzed by XRD and detected using EDS.The mechanical properties of the alloy are tested by tensile test.The results indicate that the LAY821 alloy as-cast and as-deformed are composed of α-Mg and β-Li phases,and Al_(2)Y phase distributed along the grain boundaries and among the α-Mg phase.After extrusion,rolling and intermediate annealing treatment,the alloy develops a homogeneous doublephase equiaxial crystal structure,with an average diameter reduction from 11.6 μm to 7.0 μm.The Al_(2)Y particles are diffusely distributed,with an average diameter reduction from 2.2 μm to 1.0 μm.No new phases are found in the XRD test results.The tensile property of the alloy exhibit 290.26 MPa of UTS,54.74HV of hardness,and more than 30% of elonga-tion.The improvement of the mechanical properties is due to the refined equiaxial crystalline structure and the dispersion strengthening effect of Al_(2)Y.The structure of the LAY821 alloy sheet for the hot-press laminated additive manufacturing is controllable,and the mechanical properties show no obvious anisotropy.