Room temperature deformation and mechanisms of slip transmission in oriented single-colony crystals of an alpha/beta titanium alloy

Primary creep at low homologous temperatures and low stresses has been wide ly reported in alpha/beta Ti alloys. Creep in these alloys is dependent on microstructure, with the colony microstructure showing the least creep resi stance. There exists a Burgers orientation relationship between the alpha a nd the beta phase, which has been assumed to allow for easy slip transmissi on across the alpha/beta interfaces. Constant strain rate and creep tests w ere performed on single-colony crystals of a near-alpha alloy oriented for slip along different prismatic slip systems in the a phase. A distinct anis otropy in the deformation behavior of different colony crystals is found. T he origin of this anisotropy is due to the relative misalignment of the sli p systems between the alpha and the beta phases which results in the format ion of residual dislocations during slip transmission. A simple model is pr esented based on the accumulation of residual dislocations at both the alph a/beta interface and the alpha matrix, which provides insight into the mech anism of slip transmission, strain hardening and primary creep of these col ony structures. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Scien ce Ltd. All rights reserved.