On Formation Of Texture Variations And Its Role On Planar Yield Anisotropy In A Mg-2Zn-1Ca Alloy

Magnesium alloy is widely used due to the characteristics of light weight,high specific strength and high specific stiffness.However,due to the low sliding system of magnesium alloys,it is easy to produce a strong basal texture when deformed at room temperature,which is harmful to the subsequent plasticity deformation.Nowadays the main methods to improve the forming performance of magnesium alloy sheets include:refining grains,increasing the temperature,and improving the texture.It was reported that the addition of rare earth elements can make magnesium alloy sheets form a weak base texture after rolling,and Ca elements can have a similar effect to rare earth elements.In this work,a Mg-2Zn-1Ca plate with TD-inclined off-basal orientation was cold rolled followed by annealing at temperature from 300?C to 400?C.The microstructure,the influence of the deformation mechanism during the rolling process on the texture formation,the texture evolution mechanism during the annealing process,and the factors affecting the anisotropy of mechanical properties were characterized by using XRD,EBSD and VPSC.The main contents of the the paper are as follows:（1）After cold rolling,the texture of the sheet changed from the initial weak bimodal non-basal texture along the TD to the elliptical distribution,along with prismatic{10-10}plane orientated primarily to RD.It is the initial orientation of plate that induced the activation of low CRSS deformation modes（such as basal slip,extension twinning,prismatic slip）,triggering the transformation of misorientation,and ultimately determines the distribution characteristics of the texture.（2）In the process of static recrystallization,the texture reverted to the non-basal bimodal texture,and the prismatic orientation changed to a random distribution.The reason is mainly due to the nucleation of recrystallization orientation and the uniformity of grain growth,and has nothing to do with the location of the nucleation.Most of the initial recrystallized grains are deflected to the position perpendicular to the cold rolling direction,and the c-axis of the recrystallized grains have different tilt angles away from ND in all directions along the plane,which makes the final sheet formed uneven in-plane distribution of the recrystallized texture.（3）The anisotropy of the mechanical properties of the annealed sheet when stretched in different directions is due to the difference of?₀ in different directions,and the effect of different deformation modes on?₀can be described by the CRSS/SF value.The CRSS/SF value of the grains is affected by the loading direction,which is higher along the RD direction,resulting in an increase in the overall plate?₀.In addition,the combination of the difference in CRSS/SF（?Stress）of adjacent grains and the geometric compatibility factor（m’）explains that the k value remains constant in the RD/TD direction,which reduces the effect of grain size on the anisotropy.