热浸镀Zn11Al3Mg0.2Si合金镀层微观组织实验研究

主要研究了热浸镀Zn11Al3Mg0.2Si合金镀层的微观结构及组织特征,利用扫描电镜SEM及其能谱附件EDX观察分析了锌铝镁镀层表面以及截面的微观结构、合金层的形貌、镀层中各相的成分组成,利用辉光放电发射光谱仪GD-OES分析了镀层中各元素沿深度方向的分布,利用电子探针EPMA分析了镀层中各元素的分布,利用X-射线衍射仪分析了镀层的相组成。结果表明:镀层中各元素沿镀层的深度方向呈现不均匀分布,Mg元素在镀层表面严重富集,镀层组织呈现多相混合结构,以MgZn2和Zn共晶为主,同时存在块状锌以及一层较薄的合金层。

Effect of Al addition on microstructure and mechanical properties of Mg-Gd-Zn alloys

The microstructure evolution and mechanical properties of Mg−15.3Gd−1Zn alloys with different Al contents(0,0.4,0.7 and 1.0 wt.%)were investigated.Microstructural analysis indicates that the addition of 0.4 wt.%Al facilitates the formation of 18R-LPSO phase(Mg12Gd(Al,Zn))in the Mg−Gd−Zn alloy.The contents of Al11Gd3 and Al2Gd increase with the increase of Al content,while the content of(Mg,Zn)_(3)Gd decreases.After homogenization treatment,(Mg,Zn)_(3)Gd,18R-LPSO and some Al11Gd3 phases are transformed into the high-temperature stable 14H-LPSO phases.The particulate Al−Gd phases can stimulate the nucleation of dynamic recrystallization by the particle simulated nucleation(PSN)mechanism.The tensile strength of the as-rolled alloys is improved remarkably due to the grain refinement and the fiber-like reinforcement of LPSO phase.The precipitation of theβ′phase in the peak-aged alloys can significantly improve the strength.The peak-aged alloy containing 0.4 wt.%Al achieves excellent mechanical properties and the UTS,YS and elongation are 458 MPa,375 MPa and 6.2%,respectively.

Gd含量对Al-Zn-Mg-Cu-Zr合金微观组织与力学性能的影响

采用铸锭冶金工艺制备6种Gd含量不同的A1-Zn-Mg-Cu-Zr-xGd合金。采用金相观察、力学性能测试、扫描电镜、电子探针及透射电镜等分析手段,研究质量分数x,分别为0%、0.10%、0.15%、0.20%、0.25%和0.30%的Gd对基体合金铸态及时效态显微组织和力学性能的影响。结果表明:Gd含量对A1-Zn-Mg-Cu-Zr合金的微观组织和力学性能的影响显著,当Gd含量低于0.25%时,随Gd含量的增加细化效果、强度以及伸长率都增加;当Gd含量为0.25%时,铸态组织中基体晶粒最小,达到32μm左右;此时T6态合金组织的强度和伸长率达到最高,抗拉强为624.54 MPa,屈服强度为595.00 MPa,伸长率为13.3%,且固溶组织具有良好的抗再结晶作用;而当Gd含量超过0.25%时,合金的微观的组织与力学性能变差。