样品取向对AZ31镁合金静态再结晶行为的影响

利用EBSD技术研究了样品取向对AZ31镁合金静态再结晶行为的影响.采用了沿板材法向切取的试样(0°试样)和沿板材横向切取的试样(90°试样)2种取向的样品,在150℃进行15%单轴压缩变形,然后在275℃保温不同时间进行退火实验.结果表明,0°试样15%单轴压缩变形内的变形机制以滑移为主;90°试样15%单轴压缩变形内的变形机制先以拉伸孪生为主,然后以滑移为主;由于变形机制的差异,相同压缩应变下90°试样比0°试样形变储存能要小.与0°试样相比,90°试样相同退火参数下静态再结晶开始及结束时间都被推迟.随着再结晶过程的进行,90°试样和0°试样2°—4°小角晶界含量均降低,均在30°取向差角处产生峰值;绝大多数再结晶晶粒优先在原始晶界处形核,少数再结晶晶粒在拉伸孪晶内部形核.

EFFECT OF SAMPLE ORIENTATION ON STATIC RECRYSTALLIZATION OF AZ31 MAGNESIUM ALLOY

The effect of sample orientation on static recrystallization (SRX) of AZ31 magnesium alloy was investigated with electron backscattered diffraction(EBSD) technique.Two kinds of samples, one was cut along the normal direction of the sheet(0° sample),the other along the transverse direction of the sheet(90° sample),were given 15% uniaxial compression strain at 150°C,followed by annealing at 275℃ for different times.The results show that slip dominates the deformation process during 15%uniaxial compression strain for the 0° samples.However,extension twinning firstly dominates the deformation process and then slip dominates the deformation process during 15%uniaxial compression strain for the 90°samples.Due to the different deformation mechanisms,the deformation stored energy of the 90° samples is lower than that of the 0° samples.As a result,the initiation and completion of SRX of the 90° samples are significantly retarded compared with that of the 0° samples.As SRX proceeds,the percentage of low angle grain boundaries between 2° and 4° decreases dramatically and a peak located around 30° appears in misorientation angle distribution map for both the 90° samples and the 0° samples.Most SRX grains nucleate at the original grain boundaries for both the samples. A few SRX grains nucleate within extension twins.