中文摘要：

本文利用原位EBSD技术研究了多晶纯钛在拉伸变形过程中的孪生变形行为。在0％～7.1％变形阶段，形成的孪晶为｛1122｝一次孪晶，当变形增加至16.4％时，在｛1122｝一次孪晶内形成｛1012｝二次孪晶。通过计算应力方向与晶体C轴夹角，判断出容易出现｛1122｝压缩孪晶和｛1012｝拉伸孪晶，理论计算得到的结果与实验结果一致。孪晶的形核位置为与周围相邻晶粒取向差最大的晶界处，即高角度晶界处，这为多晶材料的塑性变形模拟提供了实验参考。

英文摘要：

The twinning deformation behaviors of polycrystal pure titanium were studied by in situ EBSD technique. The results show that the primary twin formed during 0% ～7% strain is{1122} compressive twin, while the secondary{1012} tensile twin forms when the strain increases to 16？4%. The geometry angle between the loading direction and c？axis of crystal indicates that {1122}compressive twin and {1012} tensile twin are easier to form. The theoretical calculation is in well consistent with the experimental results. The nucleation site of twin is located in a grain boundary with highest misorientation comparing with the other boundaries, i. e. , high angle boundary. The results provide experimental insight into modeling of plastic deformation in HCP structured polycrystalline metals.