Effect of multi-pass cooling compression and subsequent heat treatment on microstructural and mechanical evolution of TC4 alloys

Three passes of hot compression tests of hot isostatic pressed Ti-6Al-4V alloys are carried out on a Gleeble-1500D thermo-mechanical simulator with a temperature-drop of 950-900-850 degrees C, constant strain rate of 0.01-1 s(-1), and the height reduction from 20% to 70%. Then, the subsequent solution and aging treatments are conducted on a heat treatment furnace. The corresponding results of microstructures and mechanical properties show: In the process of multi-pass deformation, dynamic recrystallization with spheroidization of lamellar a phases are the main characteristics affecting flow behaviors. With the increasing strain, lamellar a phases gradually transform from a bimodal distribution to a single peak state perpendicular to the compression direction. The decreasing length and rising thickness of lamellar a phases in the transformation process facilitate the formation of spheroidized a phases. During the heat treatment, the proportion of spheroidized a phases increases, and the spheroidization phenomenon promotes the reduction of lamellar a phases in length and increment in thickness. Lamellar a phases mainly domi-nate the contribution of microhardness in the hot compression process, and the equiaxed a phases and b transformation structures are combined to influence the mechanical properties of heat-treated Ti-6Al-4V alloys. Notably, b transformation structures contribute primarily at a higher solution temperature. (c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).