Regulation Reaserch On Microstructure And Properties Of High Strength Aluminum Alloy

In this paper,the high development of aerospace and defense technology appeal to the high properties of high strength aluminum alloy This reaseerch has employed microstructure observation methods such as OM, SEM and TEM, as well as test methods such as micro hardness test, tensile test and DSC, conductive testing, SSRT testing and EXCO testing.We have studied the effects of mircoalloying and thermalmechanical heat treatment on the microstructure and properties of high strength alloy such as Al-Cu-Mg alloy.And the conclusions were drawn as follow:(1) Trace Si addition enhances the age-hardening effect of Al-1.5Cu-4.0Mg (Wt%) alloy aged at200℃, reduces the aging time of peak hardness, and the hardness is improved. The alloy which contains0.5%Si has a higher age-harding effect than that of the alloy containing0.25%Si.(2) Trace Si addition can reduce the dislocation or dislocation loops in the microstructure of under-aged Al-1.5Cu-4.0Mg alloy, trace Si addition can promote the precipitation of S phase, the formation of T phase is restrained at the same time. When Si content reaches to0.5Wt%, the precipitation of T phase is almost suppressed.(3) Adding trace amount of Si can refine S phase, the S phase become finer as the Si content increases,and the S phase in Al-1.5Cu-4.0Mg-0.5Si alloy is finer than that of Al-1.5Cu-4.0Mg-0.25Si alloy.(4) When Al-Zn-Mg-Cu alloy is treated with final thermo-mechanical treatment (FTMT), the cold deformed alloys of FTMT craft at room temperature can significantly increases the strength of the alloy without the plasticty obviously decreased.(5) FTMT with warm deformation at160℃and200℃improve the strength of the alloy, and it simultaneously improve the elongation than that of cold deformation FTMT., and the5%deformation of FTMT can obtain both good strength and elongation.(6)In the modified RRA, which adds deformation after regression, RRCA(cold rolling after regression) can obtain high strength but low elongation, while RRWA (warm rolling after regression) can obtain both good mechanical properties of sthrength and elongation.(7) In the corrosion resistance tests of Al-Zn-Mg-Cu alloy, the alloy with cold deformation FTMT heat treatment has good SCR, but the exfoliation corrosion resistance is poor, when warm deformation at200℃is applied, the resistance to exfoliation corrosion is improved.The new RRWA process has a good combination of SCR and corrosion resistance.