高强Al-Ni系铸造铝合金的挤压铸造及强化机制

Squeeze Casting and Strengthening Mechanism of High-strength Al-Ni Cast Aluminum Alloys

为了开发新的高强铸造铝合金材料,分别采用3种铸造工艺,砂型铸造、金属型铸造和挤压铸造,制备了一种以Al-Ni共晶体系为基础的AlZn6Ni4Mg2Cu铸造铝合金材料。研究了Ni元素、热处理和铸造工艺对其微观组织、力学性能的影响规律,揭示了其强化机制。结果表明:4%(质量分数)的Ni在该铝合金中形成了大量的共晶组织(α-Al+Al_3Ni),同时改善其力学性能和铸造性能,起到了共晶强化的作用;固溶和时效热处理导致Al_3Ni相的球化和MgZn_2相的时效析出,提高了该铝合金的强度;相比砂型铸造和金属型铸造,挤压铸造时该铝合金的晶粒和Al3Ni相最细小,力学性能最佳,抗拉强度为586 MPa,断后伸长率为3.5%。由此得出:AlZn6Ni4Mg2Cu铸造铝合金的强化机制为η(MgZn_2)相的时效强化和Al_3Ni相的弥散强化,挤压铸造加T6热处理后,该铝合金的力学性能达到最佳值。

In order to develop new high-strength cast aluminum alloys, AlZn6Ni4Mg2Cu cast aluminum alloys based on Al-Ni eutectic system were prepared by sand casting, permanent-mold casting and squeeze casting processes. The influence of Ni element, casting process and heat treatment on the microstructure and mechanical properties was studied. The results indicate 4% Ni（mass fraction） forms a great deal of eutectic structure（α-Al＋Al_3Ni） in the aluminum alloy. Al_3Ni improves casting properties and mechanical properties of the alloy and plays a role of eutectic strengthening. Solution and aging treatment cause globalization of Al_3Ni phases and aging precipitation of MgZn_2 and Al_2Cu phases; as a result, the strength of AlZn6Ni4Mg2Cu cast aluminum alloy is increased. Compared to the samples by sand casting and permanent-mold casting, the sample by squeeze casting possesses the finest grain and Al_3Ni phase, as well as the optimum mechanical properties, whose tensile strength is 586 MPa, and the elongation percent is 3.5%. It is concluded that the strengthening mechanism of AlZn6Ni4Mg2Cu cast aluminum alloy is aging strengthening of η（MgZn_2） phases and dispersion strengthening of Al_3Ni phases. The mechanical properties reach their highest values by squeeze casting and T6 heat treatment.