Microstructure design and in-situ investigation of TRIP/TWIP effects in a forged dual-phase Ti-10V-2Fe-3Al alloy

Strain-transformable Ti-based alloys are known to display a superior combination of strength, ductility and strain-hardening and attracted considerable interest on recent years. They generally still display, however, a limited yield strength that can be possibly overcome by further precipitation strengthening of the developed systems. In that work, we developed a design strategy to reach a forged dual-phase (α+β) microstructure with TRIP/TWIP properties in a Ti-10V-2Fe-3Al alloy. The results showed an excellent combination of mechanical properties due to the strain-transformable deformed beta-matrix. The investigation on the deformation mechanisms in the Ti-10V-2Fe-3Al alloy was accurately performed by means of both in-situ synchrotron XRD, mechanical testing followed by SEM/EBSD mapping and 'post mortem' TEM microstructural analyses. Combined Twinning Induced Plasticity (TWIP) and Transformation Induced Plasticity (TRIP) effects were shown to be intensively activated in the alloy. The particular role of stain-induced martensite alpha '', acting as a relaxation mechanism at the alpha/beta interfaces, as well as the strong interactions between mechanical twins and primary alpha nodules were particularly highlighted. (authors)