退火对冷轧的高纯Al-4Cu合金微观组织和性能的影响

摘要

将尺寸为φ140 mm×130 mm作为靶材的高纯Al-4%Cu合金铸锭锻造、固溶处理及压下量为80%冷轧后,分别在150 ℃、200 ℃、250 ℃和300 ℃保温30 min退火.通过拉伸试验、硬度测定、X射线衍射和透射电镜研究了退火温度对合金显微组织和力学性能的影响.结果表明:在200 ℃退火的合金中有少量Al2Cu相析出;在250 ℃退火后,合金中析出大量针状纳米级θ'(Al2Cu)相,并弥散分布于基体中,显著提高了靶材的抗冲击性能;在300 ℃退火的合金中第二相明显粗化,其尺寸约为1 μm,易导致冲击过程中靶材微裂纹的产生.此外,退火后,合金的抗拉强度从冷轧态的369 MPa降低到了173 MPa,而断后伸长率则从3.5%升高到了15.6%,这说明高纯Al-4%Cu合金的第二相析出强化效果明显受到了加工硬化效果由于退火而消除的影响.%Highly pure Al-4%Cu alloy ingot 140 mm in diameter by 130 mm long,used as a target,was successively forged,solution treated,cold rolled to a reduction of 80%,and annealed at 150 ℃,200 ℃,250 ℃, and 300 ℃ for 30 min,respectively.The effect of the annealing temperatures on microstructures and mechanical properties of the alloy was investigated by means of tensile test,hardness test,X-ray diffraction and transmission electron microscope.The results showed that a small amount of Al2Cu phase was precipitated in the alloy annealed at 200 ℃,and that a large amount of needle-like nano-scale θ'phase (Al2Cu)was precipitated and dispersed in the alloy annealed at 250 ℃,rendering impact resistance of target much better,and second phase in the alloy annealed at 300 ℃ coarsened to as size as about 1 μm,being easy to result in creation of micro-crack in target during impact.Moreover,tensile strength of the alloy decreased from 369 MPa in the cold-rolled state to 173 MPa in the annealed state,whereas its elongation increased from 3.5% in the cold-rolled state to 15.6% in the annealed state, which indicated that removal of work-hardening effect as a result of the annealing exerted considerable influence on precipitation strengthening effect of the second phase for the highly pure Al-4%Cu alloy.