Influence of β Grain Orientation on the Stress‐Induced Martensite Formation in Cold‐Rolled Metastable β Ti–5Mo–5V–5Al–3Cr Alloy

Abstract

Solution‐treated metastable β Ti–5Mo–5V–5Al–3Cr (Ti 5553) alloy processed through cold rolling at strain levels of 5–45% results in stress‐induced martensitic transformations (SIMT). Further, the cold‐deformed sample is annealed at 860 °C for 5 min to achieve recrystallization and relieve internal stresses. The influence of recrystallized β grain orientations on Ti‐5553 deformation behavior is characterized using nanoindentation tests. As β grain orientation changes from near <111> to <001> direction, the alloy exhibits an increase in hardness (from ≈6.3 to ≈6.6 GPa) and a decrease in elastic modulus (from ≈127 to ≈120 GPa). It can be inferred that a threshold stress is necessary to activate SIMT in each orientation due to the stress gradient from the top surface to the indent tip at a certain penetration depth in the sample. Additionally, the influence of alloying elements (e.g., Mo, V, Al, and Cr) on β phase stability as a function of grain orientations is confirmed using the electron probe microanalyzer. Observations indicate that <111> grain orientation is most preferred, followed by <101> for promoting stress‐induced martensite, while <001> is least preferred.