显微缩松缺陷对ZL114A热处理合金力学性能的影响

Influence of Porosity Defect on Mechanical Properties of Heat Treated ZL114A Alloy

通过光学和电子显微镜(SEM/EDS)观察,研究了缩松缺陷对石膏型精铸ZL114A合金铸态和热处理态力学性能的影响。结果表明,试样的拉伸裂纹源于缩松边缘,并沿晶界向邻近缩松扩展;T5处理有助于改善ZL114A合金拉伸时缩松缺陷的敏感性,T5处理后,缩松边缘变得光滑,缩松边缘富Fe相圆整,共晶Si进一步球化,Mg2Si弥散析出,均增加了拉伸时裂纹形核和扩展阻力,从而使ZL114A合金的力学性能大幅提高。

Through the plaster-mold precision casting and T5 heat treatment, the effects of the porosity defect on the tensile properties of ZL114A alloy have been investigated by optical microscope and scanning electron microscopes （SEM/EDS）. The results show that the tensile crack of the specimen is derived from the porosity defect, and then propagates along the grAln boundary to the adjacent porosity. The T5 heat treatment helps to improve the porosity susceptibility of ZL114A alloy under a uniaxial extension. After T5 heat treatment, the walls of the shrinkage porosity are smoothed, the Fe-rich phases in the vicinity of shrinkage porosity are rounded, the eutectic Si phase is further spheroidized, and the Mg2Si phase is precipitated in the alloy. As a result, the resistance of the nucleation and propagation of the cracks is increased. Thus, the mechanical properties ofZL114A alloy are greatly improved.