Research 6061 Aluminum Thermal Deformation And Aging Behavior

The hot-compression behavior of6061aluminum alloy at elevated temperature wasstudied by Gleeble-3500hot simulator with the deformation temperature range of375-500℃, the strain rate range of0.001-10s^-1and the maximum reduction50%. The relationshipbetween flow stress and deformation temperature as well as strain rate of6061aluminumalloy was analyzed. The deformation constitutive equation at elevated temperature wasestablished. According to the materials dynamic model, the hot processing maps werecalculated and analyzed through compulating the sensitivity index m, energy consumptionefficiency η and stability function ξ（ε|.）of the6061aluminum alloy under differentdeformation temperature and strain rate. After all samples were solutionized at540°C,they were aging at different time and temperature. Measure the hardness of samples withdifferent aging state; analyse samples’ microstructure with electron microscope and TEM,then determining the best aging process. The results show that:The flow stress gets smaller with the increase of deformation temperature at the samestrain rate, and becomes larger with the increase of strain rate at the same temperature.The flow stress of6061aluminum alloy during hot-compression can be described byZener-Hollomon parameter under the laboratory conditions, and the deformationactivation energy is^-174.350KJ/mol and stress exponent n is6.63. The process of hotdeformation in the temperature range and different strain rate can be attained by the maps,which deformation temperature is375-400℃, strain rate is around0.001-0.01s^-1. aftersolutionized many big second phase particles decreased and many tiny second phaseparticles appeared in the samples. And the hardness of solutionized samples has beengreatly improved. After aged process the hardness of samples were improved more. Whenthe aging treatment temperature was^-150℃and175℃, the hardness of samples wasimproved in the aging treatment process. When the aging treatment temperature was200℃, the hardness of the samples was improve at first. I got the biggest hardness at thesix hour of aging process, which is^-114.26HV.Then the hardness decline as aging processwent on.After aged for3hours at200℃，the samples precipitate many tiny needle-likesecond phase particle；After aged for6hours at200℃，granular second phase particle and needle-like second phase particle were found in the microstructure. But the dimension ofsecond phase particle was bigger than the samples which was aged for3hours. After agedfor7hours at200℃, the form of second phase particle was similar to the samples whichwas aged for6hours, but the dimension of second phase particle is much bigger. Duringaging process, grain boundary precipitate large, discrete second phase particle on theboundary of grain; and we found precipitates free zone near the boundary of grain, whichwas wider as aging process went on.