Zn层添加AZ31/7075合金复合成形工艺及组织与性能研究EI北大核心CSCD

通过在异种材料界面添加厚度为100μm的Zn箔,采用预挤压与孔型轧制复合工艺成功制备出AZ31/7075复合材料,并利用光学显微镜(OM)、扫描电子显微镜(SEM)、能谱分析(EDS)对复合界面进行表征及显微硬度测试,探究Zn过渡层在挤压复合孔型轧制过程中对产品的影响。结果表明:7075硬质铝合金芯部可细化AZ31镁合金,引入Zn过渡层可减少或者避免镁铝系金属间化合物生成;挤压及变形温升使Mg-Zn互扩散形成的低熔点共晶相熔化,同时加速元素自固相向液相扩散;然而降温冷却使Mg-Zn扩散层易出现不连续裂缝,但后续孔型轧制可显著改善;Mg-Zn扩散层经变形生成的MgZn_(2)金属间化合物具备较高的显微硬度(161HV),但Mg-Zn扩散层变形后厚度则较薄,结合层整体硬度变化不明显。

Fabrication,microstructure and property of AZ31/7075 composites with Zn intermediate layer

AZ31/7075 composite with the addition of Zn foil (about 100 μm in thickness) in the dissimilar material interface was successfully fabricated by pre-extrusion+caliber rolling composite process. The microstructure evolution especially for the composite interface was characterized by optical microscopy (OM), scanning electron microscopy (SEM) with energy dispersive spectrometer (EDS) and the microhardness test was also performed. The effect of the Zn intermediate layer on the product during the extrusion and caliber rolling was explored. The results show the hard 7075 Al alloy as the core can refine the grain size of AZ31 alloy. In addition, introducing Zn intermediate layer can reduce or completely avoid the formation of Mg-Al intermetallic compounds. The temperature increased by extrusion and deformation results in the remelting of eutectic Mg-Zn phase, and the diffusion of both elements from the solid to the liquid phase are accelerated. However, discontinuous cracks can be observed in the Mg-Zn diffusion layer but will be healed after caliber rolling. The MgZn₂ intermetallic compound generated at Mg-Zn diffusion layer has high hardness (161HV), but the overall hardness of bonding layer is not changed a lot due to thinner thickness of the Mg-Zn diffusion layer after deformation.