Study On The Preparation And Microstructure Of Heterogeneous Laminated Structure Al-3%Cu Alloy

This article aims to improve the comprehensive mechanical properties of aluminum-copper alloys,and Al-3%Cu alloy is selected as the experimental material.Rolled Al-3%Cu alloy and annealed Al-3%Cu alloy samples were alternately laminated,and pre-welded by diffusion bonding on a Gleeble-3800 thermal simulation machine.Then,the pre-welded samples were hydraulically pressed to the target thickness to prepare the heterogeneous laminated Al-3%Cu alloy.The microstructures of samples treated by different thermomechanical process were studied,and the following conclusions were drawn:(1)Hold for 60min at 200℃,followed by continuing to heat up to 300℃ for 3min,diffusion bonding of 38%deformation was carried out at a strain rate of 0.1s-1.There is no crack in the welding interface,and a stably pre-welding and outstanding Al-3%Cu alloy can be obtained.(2)Heterogeneous laminated Al-3%Cu alloy was prepared by holding at 200℃for 60min,loading a constant connection pressure of 25MPa,pre-welding at 300℃at a strain rate of 0.1s-1 at 38%deformation,and then hydraulically pressing to 1mm at room temperature.The results show that the grain size and the volume fraction of precipitates in the soft domain(AR layer)are different from those in the hard domain(CR layer),and there is also a difference in grain size and dislocation density in a single layer.The heterogeneous region with equiaxed grains is formed on the interface,and therefore the heterogeneous deformation near interface induces additional strengthening and work hardening.Compared with the rolled Al-3%Cu with 80%deformation(301.44MPa),the heterogeneous laminated structure Al-3%Cu alloy keeps the comparable tensile strength(310.16MPa),increased by 2.9%,However,the uniform elongation upgrades from 2.5%to 4.1%,increased by 64%,achieving an excellent combination of high strength and good ductility.(3)Under the three annealing processes of 200℃ for 3h,250℃ for 3h,and 300℃ for 3h,the soft domain in the heterogeneous laminated structure Al-3%Cu alloy has a basically consistent coarse grain microstructure,ensuring the basic plasticity and having nothing to do with the increase in strength.Under the annealing process of 200℃ for 3h,the hard domain accounts for the highest proportion in heterogeneous area.The hard domain can limit the geometrically necessary dislocations generated in the soft domain to the greatest extent,resulting in a large strain gradient and heterogeneous deformation-induced stress,producing additional work hardening and increasing the strength.At the same time,a large amount of second phases such as Al2Cu are precipitated in the heterogeneous domain,which can also resist dislocation slip and increase the strength.Moreover,compared to the deformed sample(311.07MPa),the one of annealing at 200℃ for 3h keeps the strength basically unchanged(308MPa),whereas the uniform elongation increases 97.4%(from 3.8%to 7.5%),further improving the comprehensive mechanical properties.