Mg-Y及AZ31镁合金高温变形过程中微观织构的演化

Microtexture evolution in Mg-Y and AZ31 Mg alloy during hot deformation

在温度为723 K、应变速度为3×10-3 s-1的条件下,对Mg-Y及AZ31镁合金挤压棒材进行单向压缩变形,利用OM、SEM和EBSD观察、分析Y对挤压棒材动态再结晶和微观织构的影响。结果表明:AZ31镁合金在真应变ε=0.2时发生明显的动态再结晶,在ε=0.5时,动态再结晶晶粒的体积分数高达80%以上;而Mg-Y合金在真应变ε=0.4时,动态再结晶体积分数尚不足10%,Y对镁合金动态再结晶有显著的阻碍作用;AZ31镁合金变形时,几乎所有晶粒的基面趋向于由变形前平行于压缩方向转至垂直于压缩方向,导致基面织构在ε=1.2时发生近90°的转动;Mg-Y合金则只有小部分晶粒发生转动,转动所形成的择优取向在动态再结晶后显著弱化,并导致取向分布更加随机;Y的添加可导致镁合金基面织构在动态再结晶后显著弱化。

The effects of Y on the dynamic recrystallization（DRX） and microtexture evolution of hot deformed Mg alloy were studied by optical,SEM and EBSD microscopy.For this purpose,AZ31 and Mg-Y alloy bars were compressed at strain rate of 3×10-3 s-1 and at temperature of 723 K.The results show that DRX frequently takes place in AZ31 Mg alloy just after being compressed to strained ε=0.2 and the volume fraction of DRX grains is more than 80% after further being compressed to strained 0.5.Whereas alloying by Y retarded DRX,the fraction of DRX in Mg-Y alloy is less than 10% even at the strain of 0.4.In AZ31 Mg alloy,the alignment of the basal planes initially parallel to the compression direction is rotated gradually by compression and approaches perpendicular to the compression direction in high strain and the basal texture is rotated by about 90o at the strain of 1.2.But in Mg-Y alloy,only a few grains rotate to be perpendicular to the compression direction with increasing strain.The basal texture caused by the rotated grains is significantly weakened and the orientation distribution becomes more random after DRX.The basal texture of Mg alloy can be significantly weakened after DRX by the addition of Y.