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采用光学显微镜(OM)、扫描电镜(SEM)、能谱分析(EDS)以及X射线衍射分析(XRD)等手段,研究了Ni含量对Mg98-xGd2Nix(摩尔分数,下同,x=0,0.5,1.0)合金组织的影响。结果表明,铸态下,不含Ni的Mg98Gd2合金组织由初生树枝状α-Mg和分布在树枝间的少量共晶第二相Mg5Gd相组成;添加0.5%的Ni后,合金中Mg5Gd相消失而出现第二相X-Mg12GdNi相,其面积分数达到27%;Ni含量增加至1%时,合金相组成未发生变化,X相面积分数增至42%。在500℃固溶热处理时,随着固溶时间延长,Mg98Gd2合金中第二相Mg5Gd相逐渐溶入基体,而固溶时间达到20h,含Ni的Mg97.5Gd2Ni0.5和Mg97Gd2Ni1合金中第二相X相未发生明显溶解,且基体α-Mg的二次枝晶臂未见明显长大,表明X相具有优良的热稳定性并能有效抑制基体α-Mg的长大。
The effect of Ni content on the microstructure of Mg98-xGd2Nix (molar fraction, the same below, x = 0, 0.5) was studied by OM, SEM, EDS and XRD. , 1.0) the effect of the alloy structure. The results show that the as-cast Ni-free Mg98Gd2 alloy consists of primary dendritic α-Mg and a small amount of eutectic second-phase Mg5Gd phase distributed between the dendrites. When 0.5% Ni is added, the Mg5Gd phase in the alloy disappears The second phase X-Mg12GdNi phase, the area fraction of 27%; Ni content increased to 1%, the alloy phase composition did not change, X-phase area fraction increased to 42%. At 500 ℃, the second phase Mg5Gd gradually dissolves into the matrix and the solution time reaches 20h with increasing solution time, and the second phase in Mg97.5Gd2Ni0.5 and Mg97Gd2Ni1 alloys containing Ni The phase X did not dissolve obviously, and the secondary dendritic arm of the matrix α-Mg did not grow obviously, indicating that the phase X has excellent thermal stability and can effectively inhibit the growth of matrix α-Mg.