Zn含量对Al-Si-Mg合金中Mg_(2)Si时效析出行为的影响

Effects of Zn Content on the Aging Precipitation Behavior of Mg_(2)Si in Al-Si-Mg Alloy

采用金相显微镜(OM)、扫描电镜(SEM)、拉伸试验机及硬度测试仪,研究了不同Zn含量Al-Si-Zn-Mg合金的微观组织和力学性能。采用差示扫描量热法(DSC)研究了Mg_(2)Si相的时效析出行为,并结合Avrami-Johnson-Mehl(AJM)方程分析了Zn含量对合金时效析出动力学的影响。结果表明,随着Zn含量增加,Al-Si-Zn-Mg合金的峰值时效硬度和强度逐渐提高,伸长率逐渐降低,而峰值时效时间逐渐缩短。Zn均匀地分布在合金中,加Zn对合金的微观组织无明显影响。但Zn阻碍了Mg原子向Si团簇的迁移,提高了Mg-Si溶质原子团簇和G.P.区的析出激活能,并在随后的升温过程中加速了Mg-Si溶质原子团簇和G.P.区的溶解,使得Mg-Si团簇的尺寸减小。同时Zn的加入增加了基体的晶格畸变能,促进了Mg、Si原子从基体迁移形成更多Mg-Si团簇和Mg-Zn-Si团簇,增加了β″相的形核质点,促进了β″相的析出,提高了时效响应速率。

The microstructure and mechanical properties of Al-Si-Zn-Mg alloys with different Zn contents were investigated by metallographic microscope(OM),scanning electron microscope(SEM),tensile testing machine and microhardness tester.The effects of Zn contents on aging precipitation behavior of Mg_(2)Si phase in Al-Si-Mg alloy were analyzed by differential scanning calorimetry(DSC),combined with Avrami-Johnson-Mehl(AJM)equation.The results indicate that peak aging strength and hardness of Al-Si-Zn-Mg alloys are gradually increased with the increase of Zn contents,while elongation is decreased and peak aging time is gradually shortened correspondingly.Zn is evenly distributed in the alloy,and addition of Zn has little effect on the microstructure,which,however,improves the precipitation activation energy of Mg-Si solute atomic clusters and G.P.zone by hindering the migration of Mg atoms to Si clusters,and accelerates the dissolution of Mg-Si solute atomic clusters and G.P.zone during the subsequent heating process,resulting in the dimension reduction of Mg-Si clusters.Furthermore,the lattice distortion energy of the matrix is increased,and the migration of Mg and Si atoms from the matrix to form more Mg-Si and Mg-Zn-Si clusters is promoted after Zn addition,which increase the nucleation particles of the β″phase,promoting the precipitation ofβ″phase and aging response rate.