Nd对Mg-6Al铸态合金拉伸性能的影响

Effects of Nd on Tensile Properties of Mg-6Al As-Cast Alloy

研究Nd对Mg-6Al铸态合金拉伸性能的影响。结果表明:室温和175℃下,Mg-6Al-xNd(x=0,2,4,6,质量分数,下同)合金的屈服强度随Nd含量增加而增加,在6.0%Nd时达到最大;抗拉强度和延伸率在4.0%Nd时达到最大,当Nd含量上升至6.0%时,两者均有少量下降。组织分析表明,Nd在Mg-6Al中以针状Al11Nd3和多边形状Al2Nd相存在,其中前者含量明显高于后者,为主要析出相。Al11Nd3相析出于枝晶界和晶界,有效细化了枝晶间距和晶粒度。通过建立软硬体复合模型对合金拉伸过程进行力学分析,并结合拉伸断口观察,综合认为Mg-6Al-xNd合金拉伸性能的提高主要归结于Al11Nd3相引起的细晶强化和第二相强化作用。Nd含量达到6.0%时合金抗拉强度和延伸率出现少量下降,主要归结于大块脆性相Al2Nd含量的增加。

The effects of Nd on the tensile properties of Mg-6Al as-cast alloy were studied. Results show that the yielding strengths of Mg-6Al-xNd (x=0, 2, 4, 6; mass fraction) alloys at room temperature and 175°C increased with the Nd content increasing and reached the maximum value at the content of 6.0%Nd. The ultimate tensile strengths and elongations of these alloys at room temperature and 175°C reached their maximum values at the content of 4.0%Nd. Both the ultimate strength and the elongation decreased slightly when the content of Nd increased from 4.0% to 6.0%, which is mainly due to the increase in the brittle phase of Al2Nd. The microstructure analysis indicates that Nd exists in the Mg-6Al alloy in the form of needle-like Al11Nd3 phase and polygonal Al2Nd phase and the amount of Al11Nd3 is much more than that of Al2Nd. The Al11Nd3 phase precipitates at the dendritic and grain boundaries resulting in the obvious refinement of the interdendritic space and grains. The improvement in tensile properties of Mg-6Al-xNd (x=2, 4, 6) alloys is mainly attributed to the grain refinement strengthening and the second phase strengthening caused by the Al11Nd3 phase, which is concluded from the mechanics analysis of the tensile process by hard-soft section model and the tensile fracture observation.