Y元素对铸造Al-2.2Li-1.5Cu合金晶粒细化和力学性能的影响

Effects of Element Y on Grain Refinement and Mechanical Properties of Cast Al-2.2Li-1.5Cu-Based Alloy

摘要:

探究了微量0.1wt% Y元素的加入对于铸造Al-2.2Li-1.5Cu-0.5Mg-1Zn-0.2Zr-0.2Sc合金在铸态及热处理态下晶粒细化和力学性能的影响。结果表明：添加0.1wt% Y元素到Al-2.2Li-1.5Cu-0.5Mg-1Zn-0.2Zr-0.2Sc合金中，能够提升Al₃(Sc, Zr)相的形核温度，导致Al₃(Sc, Zr)相优先析出，增加了其在基体中的分布数量。并且，Al₃(Sc, Zr)相作为α-Al基体中的非均质形核位点，能够加速形核，细化晶粒。Y元素的加入改变了铸态合金晶界处的析出相特征，使得初始在晶界呈连续粗大条状分布的第二相转变为了断续点状、棒状分布，并且尺寸更小、数量更多。在细晶强化和沉淀强化的共同作用下，经过175 ℃/10 h时效处理后Al-2.2Li-1.5Cu-0.5Mg-1Zn-0.2Zr-0.2Sc-0.1Y合金极限抗拉伸强度达到了412 MPa，延伸率为6.3%，相较于未加入Y元素的合金抗拉伸强度和延伸率分别提高了16.1%和53.7%。

Abstract:

The effect of trace addition of 0.1wt% Y on the grain refinement and mechanical properties of Al-2.2Li-1.5Cu-0.5Mg-1Zn-0.2Zr-0.2Sc alloys at as-cast and heat-treated states was investigated. Results show that the addition of 0.1wt% Y into the Al-2.2Li-1.5Cu-0.5Mg-1Zn-0.2Zr-0.2Sc alloys can elevate the nucleation temperature of the Al₃(Sc, Zr) phase, leading to the preferential precipitation of the Al₃(Sc, Zr) phase and increasing the amount of Al₃(Sc, Zr) phase in the matrix. Al₃(Sc, Zr) phase can also act as a heterogeneous nucleation site in the α-Al matrix to promote nucleation and refine grains. The addition of element Y changes the precipitation phase characteristics at the grain boundaries in the as-cast alloy, which changes the distribution characteristics of secondary phases from initially continuous and coarse strip-like distribution at grain boundaries into the discontinuous dot-like and rod-like distribution. Besides, the size of secondary phases becomes smaller and their amount increases. Under the combined effects of grain refinement strengthening and precipitation strengthening, the Al-2.2Li-1.5Cu-0.5Mg-1Zn-0.2Zr-0.2Sc-0.1Y alloy after 175 °C/10 h aging treatment achieves an ultimate tensile strength of 412 MPa and an elongation of 6.3%. Compared with those of the alloy without Y addition, the ultimate tensile strength and elongation of the added alloy increase by 16.1% and 53.7%, respectively.