Effects of Cu and Mg on thixoformability and mechanical properties of aluminium alloy 2014

Cu和Mg对2014铝合金触变成形性和力学性能的影响（英文）

Thixoforming is a processing method that deforms metal in a semisolid state.The advantages of this process include the production of parts with good surface finish,fine microstructures and superior mechanical properties.However,the process mostly produces parts from aluminium cast grades,thereby not fully utilising the true potential of this method.Hence,thermodynamic modelling can be used to formulate alloy compositions that favour this processing method.Here,the effects of reducing copper content and increasing silicon and magnesium contents on the thixoformability of aluminium alloy 2014 were presented.The work consists of both the modelling and experimental validation.Results showed that by increasing Si and decreasing Cu content in the alloy,the solidification interval temperature was decreased and the temperature working window between the stipulated liquid fractions was widened,two of the characteristics favouring the process.A high solid-solution temperature employed resulted in the dissolution of unfavourable Mg2Si compound.An increase in Mg content used also resulted in the formation of the compactπ-Al8FeMg3Si6 phase and the decrease in the amount of the sharp and plate-like structure of theβ-Al5FeSi phase,improving the strength of the modified alloy.Subsequent T6 heat treatment successfully further increased the strength of the modified alloy.

触变成形是使金属在半固态时发生变形的一种加工方法。该工艺的优点包括具有良好的表面光洁度,细小的显微组织和优越的力学性能,然而,该工艺主要是用铝铸件生产零件,没有充分利用其真正潜力。因此,可用热力学模拟进行合金成分设计。研究减少铜含量和增加硅、镁含量对2014铝合金触变成形的影响,包括模拟和实验验证两部分。结果表明,增加合金中硅含量和降低铜含量,可以降低合金的凝固区间温度,扩大特定液相分数之间的工作温度窗口,这对该工艺有利。高的固溶温度导致Mg2Si化合物的分解。Mg含量的增加导致致密π-Al8FeMg3Si6相的形成和尖片状结构β-Al5FeSi相的减少,提高合金的强度。后续T6热处理进一步提高改性合金的强度。