稀土Ho对Al-Zn-Mg-Cu系高强铝合金显微组织和力学性能的影响

[目的]为了提高Al-Zn-Mg-Cu系高强铝合金的综合性能,研究了稀土钬(Ho)对Al-Zn-Mg-Cu系高强铝合金显微组织及力学性能的影响。[方法]采用金相显微镜、扫描电镜观察、能谱仪和拉伸试验等方法对稀土钬(Ho)改性Al-Zn-Mg-Cu系高强铝合金显微组织和力学性能进行了研究。[结果]加入Ho能够细化基体组织、净化晶界,使呈网状连续分布的晶界变为断续的岛状和鱼骨状;当稀土Ho的含量为0.5%时,晶粒达到最小最细状态,且合金熔铸缺陷明显减少,合金的抗拉强度为244 MPa,伸长率为2.92%,韧性达到最大值;随着Ho含量的增加,合金中生成了一种新相Al_3Ho,该相较软,析出在晶界,从而降低了合金的硬度。[结论]加入适量稀土元素Ho可以有效细化Al-Zn-Mg-Cu系高强铝合金的组织,显著提高合金的塑性及韧性,但硬度下降。

Effects of Ho on Microstructure and Mechanical Properties of Al-Zn-Mg-Cu High Strength Aluminum Alloy

[Objective] In order to improve the comprehensive of Al-Zn-Mg-Cu high strength aluminum alloy, the effects of holmium (Ho) on the microstructure and mechanical properties of high strength aluminum alloy were investigated.[Methods] Metallographic microscope, scanning electron microscopy(SEM), energy dispersivespectroscopy(EDS)and various testing machines were used to analyze Ho effects on the microstructures and mechanical properties of Al-Zn-Mg-Cu high strength aluminum alloy.[Results] The addition of Ho not only refines matrix organization but also purifies grain boundary, changing the net-like continuous distribution of grain boundary to intermittent island and herringbone.When the Ho is added to 0.5%, fine grain reaches to the minimized state, which significantly reduces the alloy casting defects, resulting in the maximum of tensile strength (244 MPa), elongation percentage (2.92%) and toughness in Al-Zn-Mg-Cu-Ho high strength aluminum alloy.The hardness of alloy reduces with the increase in the addition of Ho, because a new soft phase Al₃Ho is generated.[Conclusion] Appropriate addition of Ho can effectively increase the tensile strength and ductility of Al-Zn-Mg-Cu-Ho high strength aluminum alloy due to the fine-grained strength, but high Ho content can decrease the hardness.