Cu元素和RE含量对耐热铝硅合金组织及力学性能的影响

Effects of the Cu and RE Contents on the Microstructure and Mechanical Properties of Heat-resistant Al-Si Alloys

过共晶铝硅合金因其优良的耐热性而受到汽车领域的广泛关注,但随着材料服役环境的日益严苛,进一步提升过共晶铝硅合金综合性能至关重要。针对过共晶Al-14Si-xCu-1Ni-0.5Mg-0.5Mn-yRE合金(简称Al-14Si-xCu-1Ni-yRE合金,x=2、3、4,y=0.1、0.3、0.5,质量分数,%),通过X射线衍射仪(XRD)、光学显微镜(OM)、扫描电子显微镜(SEM)、拉伸测试等表征手段研究了不同Cu含量和RE(La+Ce混合稀土)含量对T6态合金微观组织及力学性能的影响规律。结果表明,随着Cu含量的增加,Al-14Si-xCu-1Ni-0.5RE合金中富Cu相(如Al_(2)Cu、Al CuNi相等)数量不断增多,特别是当Cu含量添加至4%时,合金中甚至存在大量的长针状AlSiCuNiRE相,从而割裂基体,合金伸长率不断下降,无法满足实际应用需求。当Cu含量为3%时,Al-14Si-3Cu-1Ni-0.5RE合金表现出最佳力学性能,合金的室温抗拉强度为348.2 MPa、高温抗拉强度为180.3 MPa、室温伸长率为1.91%。此外,随着RE含量的不断增加,Al-14Si-3Cu-1Ni-yRE合金中共晶Si的变质效果有所优化,但长针状富RE相也不断增多。当RE含量为0.3%时,Al-14Si-3Cu-1Ni-0.3RE合金的室温抗拉强度、高温抗拉强度和室温伸长率分别达到354.3 MPa、185.5 MPa和2.1%。

Hypereutectic Al-Si alloys have received much attention in the automotive field due to their excellent heat resistance,but as the service environment of these materials becomes increasingly demanding,it is crucial to further improve the overall performance of hypereutectic Al-Si alloys.In this paper,the effects of different Cu contents and RE(La+Ce mixed rare earth)contents on the microstructures and mechanical properties of hypereutectic Al-14Si-xCu-1Ni-0.5Mg-0.5Mn-yRE alloys(referred to as Al-14Si-xCu-1Ni-yRE alloys;x=2,3,4 wt.%;y=0.1,0.3,0.5 wt.%)in the T6 state were investigated via analytical methods,including XRD,OM,SEM,and tensile tests.The results show that the number of Cu-rich phases(e.g.,Al_(2)Cu and AlCuNi phases)in the Al-14Si-xCu-1Ni-0.5RE alloy increases with increasing Cu content.In particular,when the Cu content is increased to 4 wt.%,a large number of long needle-like AlSiCuNiRE precipitates even exist in the alloy,which split the matrix.The alloy elongation consequently decreases continuously,which cannot satisfy practical application requirements.When the Cu content is 3 wt.%,the Al-14Si-3Cu-1Ni-0.5RE alloy shows the best mechanical properties,the room temperature tensile strength of the alloy is 348.2 MPa,the high temperature tensile strength is 180.3 MPa,and the room temperature elongation is 1.91%.In addition,the metamorphic effect of eutectic Si in Al-14Si-3Cu-1Ni-yRE alloys is optimized with increasing RE content,but the amount of long needle-like RE-rich phase continues to increase.The room temperature tensile strength,high temperature tensile strength and room temperature elongation of the Al-14Si-3Cu-1Ni-0.3RE alloy reach 354.3 MPa,185.5 MPa and 2.1%,respectively,when the RE content is 0.3 wt.%.