原位观察共晶硅对Al-20%Si合金裂纹形成与扩展的影响

Effect of eutectic silicon on crack formation and propagation of Al-20%Si alloy by in-situ observation

采用共聚焦激光扫描显微镜原位观察了Al-20%Si合金在拉伸过程中裂纹形成与扩展过程,研究了共晶硅对Al-20%Si合金裂纹形成、扩展的影响。结果发现:随固溶温度升高,Al-20%Si合金共晶硅粒化效果显著。铸态Al-20%Si合金拉伸过程中在针状共晶硅处容易产生裂纹,且裂纹主要在共晶硅之间扩展。经560℃固溶6 h,190℃时效10 h后,合金中针状共晶硅完全转变为颗粒状,有效降低了裂纹扩展速度,合金的抗拉强度和塑性明显提高。

Crack formation and propagation of Al-20%Si alloy were observed in-situ by using confocal laser scanning microscope,the effect of eutectic silicon on crack formation location and crack propagation mode of Al-20%Si alloy were studied.The results show that with the increase of solution temperature,the eutectic silicon phase in the Al-20%Si alloy changes into particles.During the tensile process,cracks easily occur at the needle-shaped eutectic silicon of the as-cast Al-20%Si alloy,and the cracks mainly propagate between the eutectic silicon.After solution at 560℃for 6 h and aging at 190℃for 10 h,the acicular eutectic silicon in the microstructure of the alloy transforms completely into granular silicon,the propagation rate is decreased,and the tensile strength and plasticity of the alloy are improved obviously.