*Article* **Study on Phase Transformation Orientation Relationship of HCP-FCC during Rolling of High Purity Titanium**

**Fengmei Bai 1,2, Qingliang Zhu 1,2, Jiaming Shen 3, Zhihan Lu 1,2, Liqiang Zhang 1,2,\*, Naqash Ali 1,2, Hongwei Zhou 3,4,\* and Xianghua Liu <sup>5</sup>**


**Abstract:** High purity titanium (Ti) thin strip was prepared by rolling with large deformation and was characterized by the means of Transmission Electron Microscopy (TEM), selected area diffraction (SAED) pattern, high-resolution (HRTEM) analysis, as well as Transmission Kikuchi Diffraction (TKD). It is found that there are face-centered cubic (FCC) Ti laths formed within the matrix of hexagonal close packing (HCP) Ti. This shows that the HCP-FCC phase transition occurred during the rolling, and a specific orientation relationship (OR) between HCP phase and FCC phase obeys 0001α//001FCC and {1010}α//{110}FCC. The ORs of HCP-FCC phase transition are deeply studied by TKD pole figure and phase transformation matrix. It is found that the derived results via pole figure and transformation matrix are equivalent, and are consistent with TEM-SAED analysis results, which proves that these two methods can effectively characterize the ORs of HCP-FCC phase transition and predict possible FCC phase variants.

**Keywords:** high purity titanium; FCC phase; TKD; pole figure; transformation matrix
