The Microstructure Evolution Of 5A02 Aluminum Alloy Under Extreme Deformation Conditions

Modern manufacturing technology makes lightweight materials and lightweight structures become the mainstream design. Aluminum alloy more and more applied in the field of aerospace and automobile, ship manufacturing. Nowadays, new high speed forming technology has become an important processing methods for aluminum alloy, and the microstructure and mechanics performance of aluminum alloy must been changed by the different conditions like high strain rate, high strain, no contact loading and so on. Based on the above research background, this paper choosed 5A02 aluminum alloy as the research object and the quasi-static compression and split Hopkinson pressure bar as the test way in order to study the effect for microstructure structure caused by high strain. And we study the differences of microstructure structure and the plastic deformation mechanism under electromagnetic forming technology and traditional high speed forming caused by high strain rhe strain of the aluminum alloy microstructure structure. Finally, this paper tested the properties of different samples. The main findings are as follows:Firstly, we used universal mechanical testing machine and split Hopkinson pressure bar to compress the samples respectively. Then EBSD and TEM were carried out to get the differences about the microstructure and defect evolutions of different samples under different strain. The results showed that in the strain of 0.85 condition nanotwin appeared but the same structure could not be found in other samples. Based on the formation mechanism of nanotwins, we proposed a physical model of nanotwins which developed by overlapping of stacking faults in the coarse-grained aluminum alloy and discuss this phenomenon in detail.Taking into account the electromagnetic drive(non-contact) deformation and the traditional mechanical drive deformation have completely different loading ways, the deformation mechanisms may also different. For this scientific problem, we futher studied the influences on deformation mechanism in two different deformation ways. The results showed that the main texture of 5A02 aluminum alloy undergoing electromagnetic forming is copper texture and brass texture while under mechanical deformation with the similar experimental conditions its texture is brass texture and copper texture decreases to almost disappear. It means that abundant cross slips had been appeared under electromagnetic forming but not happened under mechanical deformation. And dislocation cell structure was observed under electromagnetic deformation while dislocation wall structure was observed under mechanical deformation. The short range order structure(SRO) theory and the principle of the crystal sliding system explained the reasons. Short range order structures hinder dislocation motion so that planar slip happened under mechanical deformation but under electromagnetic deformation the electromagnetic force start more slip systems of crystal then wave slip happened.Finally, the paper further analyzes the influences on properties with different microstructure. Nanoindentation is for mechanical properties and found little difference in hardness. Work hardening comes up in all deformed samples. Electrochemical corrosion tested corrosion resistance and both samples have good corrosion resistance. For above results, this paper gave some explanations from the relationship between microstructure and macroscopic properties,the concrete expression of all microstructure impact its performance.