Zn含量对Mg-10Gd-6Y-xZn-0．6Zr合金显微组织、力学和阻尼性能的影响

Effects of Zn content on microstructure, mechanical properties and damping capacities of Mg-10Gd-6Y-xZn-0.6Zr alloys

采用扫描电子显微镜、能谱分析仪、X射线衍射仪和动态机械热分析仪等研究Zn含量对Mg-10Gd-6Y-xZn-0.6Zr(x=0.6,1.6,2.6,3.6,质量分数,%)合金显微组织、力学和阻尼性能的影响。结果表明:铸态下,Mg-10Gd-6Y-0.6Zn-0.6Zr合金中第二相主要为Mg5(Gd,Y,Zn),在Mg基体中,由晶界处向晶内平行生长出大量层状相;随Zn含量的增加,Mg5(Gd,Y,Zn)相减少,Mg12Zn(Y,Gd)相增多;当Zn含量达到3.6%时,第二相主要以Mg12Zn(Y,Gd)相存在,Mg基体中的层状相几乎消失。对于挤压态的Mg-10Gd-6Y-1.6Zn-0.6Zr合金,其基体中呈现大量扭曲的层状相,合金抗拉强度达到400 MPa,随着Zn含量的增加,合金强度呈下降趋势,但塑性得到改善。铸态合金的阻尼性能随Zn含量的增加先下降后上升,采用Granato-Lücke(G-L)理论和G-L图对合金阻尼性能进行了分析和讨论。

SEM, EDS, XRD and DMA （dynamic mechanical analysis） techniques were applied to investigating the effect of Zn content on microstructure, mechanical properties and damping capacities of Mg-10Gd-6Y-xZn-O.6Zr alloys （x=0.6, 1.6, 2.6, 3.6, mass fraction, %）. The results show that the major second phase in the as-cast Mg-10Gd-6Y-0.6Zn-0.6Zr alloy is Mgs（Gd, Y, Zn）. Besides, a mass of lamellar phases grow parallelly with each other from the grain boundary to the grain interior. With the increase of Zn content, Mgs（Gd, Y, Zn） phase decreases and Mgl2Zn（Y, Gd） increases continuously. When the Zn content is 3.6%, Mgl2Zn（Y, Gd） exists as the major second phase, and the lamellar phases almost disappear. The numerous distorted lamellar phases precipitate in the grain interior of the as-extruded Mg-10Gd-6Y-1.6Zn-0.6Zr alloy, whose tensile strength reaches 400 MPa. And with the increase of Zn content, the strength of the alloy decreases while the ductility is improved. Finally, the damping capacities of the as-cast Mg-10Gd-6Y-xZn-0.6Zr alloys decrease firstly and increase afterwards, which were analyzed and discussed in terms of the Granato-Lticke （G-L） theories and G-L plots.