A novel low-cost Ti-Cr-Fe -Ti alloy with TWIP effect: Sensitivity of tensile properties to microstructural characteristics

A novel low-cost Ti-4.6Cr-3Fe beta-Ti alloy with twining induced plasticity effect was designed, and its tensile properties and deformation mechanisms were sensitive to its microstructural characteristic. The received sample with the microstructure of beta matrix embedded isothermal omega (omega(iso)) precipitations exhibited the largest tensile strength (R-m), but the limited ductility (<3 %). When the solution treatment (ST) temperature increased from below to above alpha ->beta transition temperature, the microstructure changed from beta matrix with alpha(s) precipitations to beta matrix with athermal omega (omega(ath)) precipitations, and the deformation mechanisms correspondingly changed from dislocation slip to the combination of dislocation slip and {332} deformation twins. Among different treatment samples, the ST800 sample obtained a relatively good combination of R-m (1146 MPa) and elongation to failure (EL, 12.5 %). It is surprising that, as the ST temperature increased from 800 degrees C to 900 degrees C, the R-m increased from 1146 MPa to 1230 MPa, but the fracture mode changes from ductile fracture to brittle fracture due to the formation of Laves phase (TiFe2) at grain boundaries. These findings provide a basis for improving the tensile properties of Ti-4.6Cr-3Fe alloy by adjusting the microstructure, and a reference for optimizing the composition of Ti-Cr-Fe system low cost beta-Ti alloys.