超高速碰撞下体心立方纯铁的变形孪晶

Deformation Twinning in BCC Iron Under Hypervelocity Impact

采用非火药驱动二级轻气炮技术将2017Al合金弹丸以3km/s速度撞击纯铁靶板,通过光学显微镜、扫描电镜和透射电镜研究了纯铁材料的微观组织演化.根据微观组织的不同特征可将纯铁靶板分为细晶区、高密度孪晶区和低密度孪晶区.在低密度孪晶区的主要变形方式为{112}面的孪晶,而高密度孪晶区主要变形方式为{112}面的孪晶和{110}、{112}及{123}面的位错之间的交互作用.超高速碰撞下孪晶形成机制与普通变形条件下没有区别,但是孪晶形貌区别较大,高密度位错聚集在孪晶界附近造成孪晶界面模糊;螺位错在孪晶界上分解导致沿着孪晶界发生弯曲和凹痕甚至孪晶的断裂.

Deformation microstructure 3 km/s was s transmission e beneath the cr tudied by using optical leclron microscope （TE ater can be classified as of pure iron under hypervelocity impact at a speed of microscope, scanning electron microscope （SEM） and M）. The results show that the deformed microstructure three zones： fine crystal, high dense twin and low dense twin. At high dense twinning zone, the plastic deformation mechanism of BCC pure iron under hypervelocity impact is {112} deformation twinning and dislocation slips of {110}, {112} and {123}. The morphological features of twins under impact are different from the conventional deformation. The stress concentration is caused by the dense dislocations assembled adjacent the twin boundary. The kink or flaw along the twin boundary is resulted by the screw dislocations dissociation at the twin boundary.