第三组元对Mg-Sn合金铸态组织与力学性能的影响

Effects of Third Constituent on As-cast Microstructures and Mechanical Properties of Mg-Sn Alloy

利用光学显微镜、扫描电子显微镜和X射线衍射仪分析Mg-3.52Sn-xM和Mg-6.54Sn-xM(M=Al,Zn,Nd,Gd)合金的铸态组织和相组成,测试其拉伸力学性能。结果表明:在Mg-3.52Sn合金中分别添加0.91%(质量分数,下同)Al和1.03%Zn后,粗大树枝晶有所细化,小块状Mg2Sn相极少;分别添加0.92%Nd和1.10%Gd后,树枝晶明显弱化,出现较多的小块状或细短杆状化合物Mg-Sn-Nd和Mg-Sn-Gd。在Mg-6.54Sn合金分别添加0.93%Al和1.08%Zn后,树枝晶明显细化,原先趋于连续网状分布的Mg2Sn相有所破碎;分别添加0.86%Nd和0.74%Gd后,树枝晶亦明显弱化,Mg2Sn相已完全破碎成小块状并呈弥散分布或出现明显破碎,同样出现较多的小块状或细短杆状化合物Mg-SnNd和Mg-Sn-Gd。在Mg-3.52Sn和Mg-6.54Sn二元合金中添加约1%的Al和Zn能有效提高其室温和高温拉伸力学性能,而分别添加约1%的Nd和Gd则不能有效提高其室温和高温拉伸力学性能,且Nd的弱化效果更明显。

As-cast microstructures and phase compositions of Mg-3.52Sn-xM and Mg-6.54Sn-xM(M=Al,Zn,Nd,Gd)alloys were investigated by optical microscope,scanning electron microscope and X-ray diffraction.Meanwhile,the tensile mechanical properties were tested.The results show that the coarse dendrite is refined slightly and few block Mg2 Sn phase still exists when 0.91%(mass fraction,the same below)Al and 1.03%Zn are added into Mg-3.52 Sn alloy,respectively.When0.92%Nd and 1.10%Gd are added respectively,the dendrite weakens obviously and many small block or fine short rod-shaped compounds Mg-Sn-Nd and Mg-Sn-Gd can be observed.When 0.93%Al and1.08%Zn are added into Mg-6.54 Sn respectively,the dendrite is refined obviously and Mg2 Sn phase tending to precipitate in the state of continuous net begins to break slightly.When 0.86%Nd and0.74%Gd are added respectively,the dendrite weakens significantly and Mg2 Sn phase has already broken into small block completely or significantly.Meanwhile,many small block or fine short rodshaped compounds Mg-Sn-Nd and Mg-Sn-Gd can also be observed.The respective addition of about1%Al and Zn into the Mg-3.52 Sn and Mg-6.54 Sn binary alloys respectively can enhance the tensile mechanical properties namely the ambient and elevated temperatures effectively,while the respective addition of about 1%Nd and Gd cannot enhance them effectively,especially for the addition of Nd.