The Effect Of New Thermo-mechanical Treatment On Microstructure And Property Of Aluminium Alloy

The fast development of new technology such as aeronautics and space technology has put forward higher requirements on the properties of aluminum alloy. Thermo-mechanical treatment is an effective technique to improve the comprehensive properties of aluminum alloy, therefore, this paper has employed microstructure observation methods such as OM, SEM and TEM, as well as test methods such as micro hardness test, tensile test and fatigue crack growth rate test, to study the effect of thermo-mechanical treatment on the the mechanical properties and microstructure of Al-Cu-Mg alloy, Al-Cu-Li-Mg alloy and Al-Mg-Si alloy, and conclusions as follow were drawn:(1) The thermo-mechanical treatment can obviously improve the comprehensive mechanical properties of aluminum alloy, improving the strength of the aluminum alloy while maintaining good plasticity. The process has a significant effect on Al-Cu-Mg alloy, the effect on Al-Cu-Li alloy is inferior to that of Al-Cu-Mg alloy, while the effect on Al-Mg-Si alloy is relatively low.(2) The fatigue crack expansion capability of2E12alloy in TMT status is better than that of T3and T6status.(3) As the results of microstructure analysis indicates, the mechanism of TMT process which increases the comprehensive properties of aluminium alloy is the combined effect of composite structure, such as the cmplex of clusters and vacancies, entangled dislocations, substructures and G.P. zones. The differences in dislocation structure and clusters may be the cause of the fact that the effect of TMT process on Al-Cu-Mg alloy is superior to that of Al-Cu-Li and Al-Mg-Si alloy.(4) The effect of TMT process on the comprehensive properties of Al-Cu-Li alloy is lower to that of Al-Cu-Mg alloy, it is mainly because that the interaction of Mg and Li atoms, as well as the strong attraction of Mg and Cu atoms, break Li clusters and Li-Cu atom pairs, and as the Mg content is low, which restricts the quantity of formed of Cu, Mg clusters.(5) The effect of TMT process on the comprehensive properties of Al-Mg-Si alloy is relatively low, it is mainly because that the dislocations introduced during pre-deformation process are around the coarse precipitates, or piled-up near the grain boundary, which greatly differs from the dislocation structure of the other two kinds of alloys, and the shape of the G.P.zone is ellipsoid, which has an inferior strengthening effect, thus reduces the overall effect of TMT process on Al-Mg-Si alloy.