Effect Of Deformation History On Aging Behaviour Of AZ80+0.4%Ce Magnesium Alloy

In this study,hot torsion deformation of AZ80+0.4%Ce magnesium alloy was tested by Gleeble-3500 thermal simulator and then carried on aging.The strain and strain rate is directly proportional to the radio of specimen during torsion,which is proposed to study the influence of strain rate and strain effects on aging.The hardness was tested by microhardness tester,the microstructure was observed by OM and SEM,and characterization of texture evolution of Magnesium alloys was carried out by EBSD.The results show that the grains of the rod are refined after torsion,and gradient microstructure is observed at the cross section of the rod.The average grain size of the edge is smaller than that of the heart.The recrystallized grains are the smallest at the deformation temperature of 300 °C,and the grain size increases with the increase of temperature,the hardness increases with the decrease of temperature.The microstructure become more homogeneous with the increase of temperature.Fine recrystallized grains with zonal distribution can be found in the microstructure of high torsional rate(7rad/s).The recrystallization is more complete with the decrease of strain rate,and the grain size increases continuously.The cooling rate has a significant effect on high temperature(380?)and low strain rate,which already has many precipitations during slow cooling.lower temperatures and high torsional rate(7rad/sand 0.7rad/s)is not sensitive to the cooling rate.After aging treatment,the hardness value of AZ80+0.4%Ce magnesium alloy increases with the increase of aging time.The hardness value increases from the heart to the edge at the same aging time.The continuous dot precipitates are dominant at low temperature,and then the discontinuous lamellar precipitation appears and gradually dominates with the temperature increases.The precipitates appear faster at low strain rates,but the obvious precipitates at high strain rate can't be found until aging for 12 h.As the aging time increases,the area fraction of the second phase increases continuously,and the difference tends to be coherence.The aging strengthening effect of magnesium alloy is most obvious when continuous precipitation with fine dispersion in the grain or discontinuous lamellar growth densely.The texture of Mg alloy become weak during torsion.Compared with the original texture,the strength of texture become weakened.And c axis of more grains turn to ED with the increases of deformation.The texture strength of the edge is higher than that of the heart due to the existence of recrystallization texture.The proportion of low-angle boundary gradually increases with the decrease of temperature,and increases with the increase of the strain rate,indicating that the alloy has a higher degree of recrystallization dyringhigh temperature and low strain rate.