Abstract
The mechanical properties and microstructures of Al-Li-Cu-Mg-Ag alloy after different solution treatments were investigated by means of Optical Microscopy (OM), tensile test, hardness and electrical conductivity tests, Differential Scanning Calorimetry (DSC), Energy Dispersive X-ray (EDX), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Results show that the tensile strength and hardness increase firstly and then decrease with elevating solution temperature when the holding time is kept for 30 min, and the maximum strength and hardness are reached when temperature is 520°C. The mechanical properties of alloy also display similar trend, which increase firstly and then decrease with increasing solution time when alloy is treated at 520°C. The tensile strength, hardness and elongation of the alloy solution treated at 520°C/30 min are 566 Mpa(σb),512 Mpa(σ0.2), 148HB and 8.23% (δ), respectively. TEM shows that an amount of T1 (Al2CuLi) phases are finely and dispersedly distributed in Al substrates, which can be an explanation of a mixed fracture mode of transgranular and intergranular delamination cracks observed by SEM.
Highlights
Commercial aluminium-lithium-copper alloy has high specific modulus, high strength, high stiffness resistance and low density, which makes it interesting for many material scientists [1,2]
We have studied the effects of solution treatments on microstructures and physical properties of Al-Li-Cu alloy by mechanical tests, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) analysis
An enhanced tensile strength and toughness can be obtained by appropriate solution treatment that trends to make the alloy elements and precipitations redissolve into Al matrix mostly [12,13], which lead to get fine grains and facilitate further artificial aging hardness
Summary
Commercial aluminium-lithium-copper alloy has high specific modulus, high strength, high stiffness resistance and low density, which makes it interesting for many material scientists [1,2]. Since 1980s, many researchers [3] have made a lot of studies on Al-Cu-Li alloy about its physical and mechanical properties at the stage of solution-heat treatment, and they have achieved great progresses. The mechanical properties and microstructures of Al-Li-Cu alloy are very sensitive to structures of alloy solidification schemes of heat treatments and subsequent deformation conditions [4]. Alloy always gets through different heat treatment processes so as to get the mechanical properties improved. The bulk soluble phases’ elements including Cu, Li, Mg etc will re-dissolve into the alloy matrix in solution-heat treatment heating so as to get a supersaturated solution solid, which is beneficial to subsequent aging. The studies on the effects of solution treatments are significant and beneficial to get a promoted mechanical property of AlLi-Cu-Mg-Ag alloy
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