Al-Zn-Ni-Mg-Cu变形铝合金的共晶强化效应

在Al-Zn-Mg-Cu变形铝合金中加入质量分数3%～5%的Ni元素,通过共晶反应形成了大量的Al_3Ni相,除MgZn_2相时效强化以外还增加了Al_3Ni相的弥散强化作用。Ni含量的增加既改善了Al-Zn-Mg-Cu变形铝合金的铸造性能和可焊性,又提高了抗拉强度和屈服强度。Al-Zn-Ni-Mg-Cu铝合金较佳的成分为Al-5.6Zn-3.5Ni-2Mg-1Cu,其抗拉强度、屈服强度和断后伸长率分别为650 MPa、572 MPa和7.5%,焊接接头的抗拉强度和断后伸长率分别为323 MPa、2%。随着强度的增加,Al_3Ni相由界面撕裂转变为自身断裂,Ni含量的增加提高了Al_3Ni的强化效果,但不宜超过共晶点。降低Al_3Ni相的长径比能抑制Al_3Ni相的自身断裂,Al_3Ni相的均匀分布能阻碍再结晶晶粒的异常长大。

EUTECTIC STRENTHENING EFFECT OF AL-ZN-NI-MG-CU ALUMINUM ALLOY

3%~5% Ni element is added to the Al-Zn-Mg-Cu deformed aluminum alloy, and a large amount of Al3Ni phases are formed by eutectic reaction, the particle strengthening effect of the Al3Ni phases is added besides of MgZn2 aging strengthening. The increase of Ni content not only improves the casting performance and weldability of the Al-Zn-Mg-Cu deformed aluminum alloy, but also increases the tensile strength and yield strength. The preferred composition of Al-Zn-Ni-Mg-Cu aluminum alloy is Al-5.6Zn-3.5Ni-2Mg-1Cu. Its tensile strength, yield strength and elongation are 650MPa, 572MPa and 7.5%, respectively. The tensile strength and elongation of its welded joint were 323 MPa and 2%, respectively. With the increase of Zn content, the Al3Ni phase changes from interfacial tear to self-fracture. Increasing the content of Ni helps to increase the strengthening effect of Al3Ni phases, but the content of Ni cannot beyond the eutectic point.Decreasing the aspect ratio of Al3Ni particles helps to suppress the self-fracture of Al3Ni phases. Uniform distribution of Al3Ni phase helps to prevent the abnormal growing of recrystallized grains.