铸造发动机用Mg-3.5Al-RE镁合金的组织与性能研究

Study on the Microstructures and Properties of Mg-3.5Al-RE Magnesium Alloys for Casting Engine

采用真空熔炼+压铸的方法制备了Mg-3.5Al-RE镁合金(RE=La、Ce和Nd)和Mg-3.5Al-3Nd-0.9Zn-0.15Mn镁合金,研究了稀土元素和微量Zn、Mn元素对压铸镁合金物相组成、显微组织、力学性能、导热性能和流动性能的影响。结果表明,压铸Mg-3.5Al-RE镁合金主要由α-Mg基体、短棒状/鱼骨状Al_(11)RE_(3)或颗粒状Al_(2)RE相组成,平均晶粒尺寸从大至小顺序为:RE=La>RE=Ce>RE=Nd,抗拉强度、断后伸长率从高至低顺序为:RE=Nd>RE=Ce>RE=La,导热系数从高至低顺序为RE=Ce>RE=La>RE=Nd,RE=Nd时压铸镁合金具有最佳的综合拉伸性能。在Mg-3.5Al-RE镁合金中添加Zn和Mn元素后,镁合金中短棒状/鱼骨状Al_(11)Nd_(3)相明显较压铸Mg-3.5Al-3Nd镁合金少、颗粒状Al_(2)Nd相尺寸增大,室温拉伸性能与Mg-3.5Al-3Nd镁合金相当,显微硬度提高了7.02%,导热系数减小,流动长度增大。

Mg-3.5Al-RE(RE=La,Ce,and Nd)and Mg-3.5Al-3Nd-0.9Zn-0.15Mn magnesium alloys were prepared by vacuum melting and die casting.The effects of rare earth elements,trace zinc and manganese elements on the phase composition,microstructure,mechanical properties,thermal conductivity,and flow properties of die-casting magnesium alloys were studied.The results show that the die-cast Mg-3.5Al-RE magnesium alloys are mainly composed ofα-Mg matrix,short rod like/fishbone like Al(11)RE3 or granular Al2RE phase,and the average grain size from large to small is:RE=La>RE=Ce>RE=Nd.The order of tensile strength and elongation of die-cast Mg-3.5Al-RE magnesium alloys from high to low is RE=Nd>RE=Ce>RE=La,and the order of thermal conductivity from high to low is RE=Ce>RE=La>RE=Nd.When RE=Nd,the die-cast magnesium alloy has the best comprehensive tensile properties.After adding Zn and Mn elements to Mg-3.5Al-RE magnesium alloys,the short rod/fishbone like Al_(11)Nd3 phase in magnesium alloy is significantly less than that in die-cast Mg-3.5Al-3Nd magnesium alloy,and the size of the granular Al2Nd phase increases,the room temperature tensile property is equivalent to that of Mg-3.5Al-3Nd magnesium alloy,the microhardness increases by 7.02%,the number of thermal conductivity systems decreases,and the flow length increases.