增材制造Al-Zn-Mg-Cu铝合金热压缩变形及原位拉伸研究

Research on Thermal Compression Deformation and In-situ Tension of Al-Zn-Mg-Cu Aluminum Alloy by Additive Manufacturing

采用热模拟试验机(Gleeble-3500)对增材制造Al-Zn-Mg-Cu铝合金厚板进行热压缩变形试验,建立了该合金的热变形本构方程,其中变形温度75~225℃、应变速率0.01~10 s^(-1)、真应变为0.693。结果表明,增材制造Al-Zn-Mg-Cu合金的流变应力与应变速率呈正相关,而与变形温度呈负相关。该合金热压缩流变应力可用包含Z(Zener-Hollomon)参数的双曲线正弦关系来描述,该方程可用于指导增材制造Al-Zn-Mg-Cu合金板的热加工工艺。对增材制造Al-Zn-Mg-Cu合金板进行扫描电镜原位拉伸试验,发现裂纹均起源自增材制造过程中形成的脆性第二相,而非缺陷空洞。合金断口形态为增材制造逐层打印形成的片层状组织,断口表面伴有大小相间分布的等轴韧窝,断裂属于明显的韧性断裂。

The hot compression deformation test of the additive manufacturing Al-Zn-Mg-Cu aluminum alloy thick plate was carried out by thermal simulation test machine(Gleeble-3500), and the hot deformation constitutive equation of the alloy was established. The deformation temperature is 75-225 ℃, the strain rate is 0.01-10 s^(-1), and the true strain is 0.693. The results show that the flow stress of Al-Zn-Mg-Cu alloy is positively correlated with the strain rate and negatively correlated with the deformation temperature. The hot compression flow stress of the alloy can be described by hyperbolic sinusoidal relationship including Z(Zener-Hollomon) parameters. The equation can be used to guide the additive manufacturing of the alloy plate. The in-situ tensile test of the additive manufacturing Al-Zn-Mg-Cu alloy plate was carried out by SEM. The results show that the cracks originate from the brittle second phase formed in the process of additive manufacturing, rather than the defect cavity. The fracture morphology of the alloy is lamellar structure formed by layer by layer printing made of additive.There are equiaxed dimples with alternating size on the fracture surface. The fracture belongs to obvious ductile fracture.