CRYSTALLOGRAPHIC ANALYSIS OF THE RELATIONSHIP BETWEEN BCC AND HCP PHASES IN TITANIUM-ALLOYS BY KIKUCHI PATTERNS

Crystallography of ol(HCP) phase precipitated in beta (BCC) grains of a Ti-22 mass%V-4 mass%Al alloy has been studied using the Kikuchi patt erns obtained by transmission electron microscopy. The relative orient ation relationship between or precipitates and beta matrix grains was determined by an analysis of the Kikuchi patterns taken from HCP and B CC phases. The analytical error was evaluated by the study of {1 (1) o ver bar 01}(hcp) transformation twins in the martensite phase formed i n a rapidly quenched commercially pure titanium specimen. Comparison o f the experimental results obtained from the twins with the theoretica l calculation has shown that the rotation angular error was less than 0.10 degrees. The orientation relationship of intragranular ct precipi tates have a slight deviation from the exact Burgers orientation relat ionship. The average deviation angle was 0.68 degrees for the parallel plane relationship, ie., (0001)(alpha)/(110)(beta), and 0.61 degrees for the parallel direction relationship, i.e., [2 (1) over bar (1) ove r bar 0](alpha)/[1 (1) over bar 1](beta). The grain boundary a precipi tates were found to have the Potter orientation relationship rather th an the Burgers orientation relationship with one of the adjacent beta grains.