热挤压对铸态Mg-3.5Al-3.5Ca-0.6Mn合金组织与性能的影响

Influence of Hot Extrusion on Microstructure and Properties of As-casted Mg-3.5Al-3.5Ca-0.6Mn Alloy

研究了热挤压对铸态Mg-3.5Al-3.5Ca-0.6Mn合金显微组织、力学性能和耐蚀性能的影响。结果表明:热挤压能够明显细化铸态合金的组织,挤压后晶粒尺寸由80μm减小至6μm左右,沿晶界呈连续网状分布的粗大第二相被破碎成微米甚至纳米颗粒,并呈条带状分布于基体中;热挤压态合金的抗拉强度和伸长率分别达到313.9 MPa和9.3%,较铸态合金的分别提高了153.8%和564.3%;热挤压态合金的自腐蚀电位升高,高频容抗弧半径增大,自腐蚀电流密度和平均析氢速率下降;晶粒细化导致基体特别是晶界耐蚀性能的提高,呈条带状分布的第二相对腐蚀起到了屏障作用,晶粒细化后可形成相对稳定和致密的腐蚀产物膜,这些都是热挤压态合金耐蚀性能提高的主要原因。

The influence of hot extrusion on the microstructure, mechanical properties and corrosion resistance of as-casted Mg-3.5Al-3.5Ca-0.6Mn alloy was investigated. The results show that hot extrusion could refine the structure of as-casted alloy with grain size from 80μm to 6μm after hot extrusion. The continuous network-like large second phases on grain boundaries were severely broken into micron even nanoscale particles and distributed like ribbons in the matrix. The ultimate tensile strength and elongation of hot extruded alloy were 313.9 MPa and 9.3%, which was higher than that of as cast alloy by 153.8% and 564.3%, respectively. After hot extrusion, the self-corrosion potential and arc radius of high-frequency capacity increased, while the self-corrosion current density and average hydrogen evolution rates decreased. The good corrosion resistance of matrix and grain boundaries caused by grain refinement, corrosion barrier caused by ribbon-like secondary phases and relatively stable and dense corrosion product film after grain refinement were responsible for higher corrosion resistance of hot extruded alloy.