Synchronized regulation of precision-performance for double-layer thin-walled component of dissimilar titanium alloys by hot forming with in-die aging process

Simultaneously controlling the dimensional accuracy and mechanical properties of double-layered thin-walled components made of dissimilar titanium alloys poses a significant challenge. Focusing on the double-layered thin-walled component of TA15 and TC2 titanium alloys, this paper proposes a hot forming with in-die aging process (short for HFA), which comprises three steps: solution treatment at an elevated temperature, rapid hot forming, and in-die aging accompanied by stress relaxation. The synergistic effect between stress and aging accelerates stress relaxation and promotes the precipitation of the secondary α phase, thereby shortening the time required for conventional static aging. For the solution-treated TA15 alloy during the coupled process of aging and stress relaxation, the microstructure evolution mechanism involves phase transformation and stress-induced twinning in the early stage, shifting to dislocation motion and stress-induced twinning in the later stage. For the solution-treated TC2 alloy, the microstructure evolution is dominated by dislocation motion. A double-layer thin-walled component of TA15 and TC2 titanium alloys exhibiting excellent dimensional accuracy and mechanical properties was successfully fabricated using the proposed HFA process. The contour accuracy is within 0.2 mm, and the interlayer gap is below 0.08 mm. Compared with the as-received material, the room-temperature tensile strength of the formed TA15 and TC2 alloys increased by 5.9 % and 16.1 %, respectively. The novel HFA process thus offers an effective new route for manufacturing thin-walled titanium alloy components with both high strength and high precision.