冷却速率对Al-2Cu-5Ni合金相组织及力学性能影响

Effects of Cooling Rate on Phase Structure and Mechanical Properties of Al-2Cu-5Ni Alloy

通过相图热力学计算设计了平衡凝固组织仅为α-Al基体和Al_(3)CuNi相的Al-2Cu-5Ni合金,研究了冷却速率对铸态合金组织及力学性能的影响。结果表明,随着冷却速率的提高,α-Al晶粒尺寸减小。当冷却速率由3.05℃/s提升到5.58℃/s时,Al_(3)CuNi相由鱼骨团簇组织转变为颗粒团簇状,冷却速率提高至9.08℃/s时,Al_(3)CuNi相转变为短条状,合金室温抗拉强度和伸长率达到最大值,分别为218 MPa和16.15%;350℃、25 MPa稳态蠕变速率最低为2.56×10^(-5)s^(-1),蠕变机制为位错攀移。相比较冷却速率为3.05℃/s合金,抗拉强度、伸长率和抗蠕变性能分别提高了11%、37%和96%。

An Al-2Cu-5Ni alloy only containingα-Al and Al_(3)CuNi phases as equilibrium solidification structure was designed by thermodynamic phase diagram calculation,and effects of cooling rate on microstructure and mechanical properties of as-cast Al-2Cu-5Ni alloy were investigated.The results indicate that the grain size is decreased with cooling rate increase.The morphology of Al_(3)CuNi phase is transformed from fish-bone cluster to particle cluster as the cooling rate increasing from 3.05℃/s to 5.58℃/s,which is converted to short strip form with cooling rate further increasing to 9.08℃/s.Meanwhile,the tensile strength and elongation at room temperature reach the maximum value,which is 218 MPa and 16.15%,respectively.The minimum steady-state creep rate is achieved at 350℃under the stress of 25 MPa,which is 2.56×10^(-5)s^(-1),and creep mechanism is dislocation climbing.The tensile strength,elongation and creep resistance of the alloy are improved by 11%,37%and 96%,respectively,compared with those of the alloy prepared at cooling rate of 3.05℃/s.