Hot Deformation Behaviors Of ND/ZK60 Magnesium Matrix Composites At Elevated Temperatures

In this paper,we prepared ND/ZK60 magnesium matrix composites via semi-solid and hot extrusion,the hot mechanical properties were tested during different temperature,strain rates and strain on Gleeble-3500 and Instron-5982 thermal mechanical simulator.It is indicated that the composites show different deformation mechanism at varied temperature,strain rates and strain.During the hot compression,for the same strain,the content of recrystallizations of ND/ ZK60 magnesium matrix composites increases with increasing the temperature and strain rates,and the grains sizes begin growing at high temperature(350 ?)and low strain rate(0.001 s-1).When the temperature and strain rates is 200 ? and 1 s-1,with the increase of strain,the grains turn from the base plane parallel ED to vertical ED,the quantity of recrystallizations first increase and then decrease,however,the dislocation increase with increasing of strain,which leading the work hardening.For the same constant temperature,the flow stress decrease with the elevating temperatures and decreasing strain rates.The activation energy(Q)is Q=135.39 k J/mol,Zener-Hollomon function and constitutive equation ofND/ZK60 magnesium matrix composites during hot compression,(?) and (?)respectively.During the hot tensile,with the increase temperature,the DRX happened and the quantity of recrystallizations increasing.The coarse recrystallizations appear due to long time of hot tensile at high temperature(250-300 ?).The texture intensity in the grip section is equal in the gauge section nearly at low temperature(150-200 ?).However,the texture intensity in the grip section is higher than in the gauge section at high temperature,it is investigated that the deformation mechanism is dominated by dislocation slip and GBS at low temperature and high temperature during the later high temperature deformation,respectively.The DRX not happen and the stress concentration nearby ND and grain boundary was relaxed,so the flow stress is steady at the 150 ?.When the temperature is 200-300 ?,the Dynamic recrystallizations(DRX)are produced in composites,it causes the obvious work softening,the flow stress decreases at the later deformation.