挤压态Mg-xZn-2.8Nd-0.6Zr-0.6Cd合金组织与拉伸力学性能

Study on microstructure and tensile mechanical properties of as-extruded Mg-xZn-2.8Nd-0.6Zr-0.6Cd alloy

采用金相显微镜、扫描电子显微镜、透射电子显微镜、万能拉伸试验机对Mg-xZn-2.8Nd-0.6Zr-0.6Cd合金的微观组织和拉伸力学性能进行研究,讨论不同Zn含量对合金力学性能的影响。研究结果表明:随着Zn含量的增加,合金的晶粒逐渐细化,双峰晶组织明显,强度总体呈上升趋势。合金B的屈服强度明显比合金C的屈服强度高,因为晶界上第二相成份的Zn/Nd原子数比发生变化,合金B(3.85%Zn,质量分数,下同)中的Zn/Nd原子数比只为1.2左右,但是其理论值为3.10,合金C(5.20%Zn)中的Zn/Nd原子数比为3.03左右,理论比值为4.11,导致了挤压过程中动态分解产物β1′相的数量在合金B中要比合金C中密集,使得合金B的屈服强度要比合金C的高。挤压后,合金D(6.54%Zn)获得了最高的屈服强度和抗拉强度,分别为340 MPa和363 MPa,而且保持了高达9%的伸长率。

To investigate the effect of Zn on microstructures, tensile mechanical properties of extruded Mg-xZn- 2.8Nd-0.6Zr-0.6Cd alloy, the optical microscope （OM）, scanning electron microscope （SEM）, transmission electron microscope （TEM） and universal tensile test machine were introduced. The mechanical properties of alloys with different Zn contents were compared and discussed. The results show that the grain size decreases as the content of Zn increases, followed with a bimodal grain microstructure, and the tensile strength is increased in general. The yield strength of alloy B is higher than that of alloy C because of the change of atomic ratio of Zn/Nd. The ratio of Zn/Nd in alloy B is 1.2 and the nominal ratio is 3.10, but it is 3.03 and 4.11 in alloy C respectively, which causes the number of ill＇ phase precipitation in alloy B to be more than that in alloy C. Alloy D shows the highest yield strength and ultimate tensile strength, which are 340 MPa and 363 MPa, respectively, and the elongation is kept up to 9%.