Influence of microstructure on stress corrosion cra 2026 Journal of Material

This study demonstrates that engineering microstructure is a decisive lever for stress corrosion cracking (SCC) resistance in a Ti-Al-V-Mo-Zr alloy exposed to concentrated hydrochloric acid, with a refined, uniformly distributed spheroidized phase yielding the best performance. Three variants were evaluated by slow-strain-rate tensile testing (SSRT): the as-extruded lamellar S1, the high-strength partially spheroidized S2, and the high-toughness fine-grained spheroidized S3. The susceptibility to SCC decreased progressively across these variants, with I ~ SSRT ~ values of 15.4% for S1, 19.7% for S2, and 10.1% for S3. Electrochemical measurements, including potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), reveal that the corrosion resistance follows the same order (S3 > S1 > S2), with S3 exhibiting the lowest corrosion current density (6.3 × 10-7 A/cm2) and the highest charge-transfer resistance (834.6 Ω cm2), confirming its superior passive film stability. Microstructural characterization via SEM, EBSD, and TEM shows that the S3 microstructure, achieved after optimized heat treatment, is rich in spheroidized α particles and αs precipitates, featuring a dense network of α/α and α/β interfaces. These interfaces promote crack deflection and branching during propagation, enhancing energy dissipation and suppressing main-crack advancement. Collectively, the results indicate that a controlled heat-treatment protocol effectively enhances the SCC resistance of high-strength titanium alloys in aggressive acidic environments.