Optimizing the Strength and Toughness of V/Mo-Modified 0.22C-5.24Mn Steel by Short-Time Partial Austenitization...

Area of Science:

• Materials Science
• Metallurgy
• Physical Metallurgy

Background:

• Achieving a balance between high yield strength and low-temperature toughness in advanced steels is a significant challenge.
• Traditional heat treatments often compromise one property when optimizing the other.
• V/Mo-bearing advanced high-strength steels (AHSS) offer potential but require tailored processing.

Purpose of the Study:

• To investigate the effect of the short-time partial austenitization (SPA) process on the microstructure and mechanical properties of V/Mo-bearing 0.22C-5.24Mn steel.
• To achieve a synergistic improvement in yield strength and low-temperature toughness.
• To understand the role of precipitate morphology and multiphase hierarchical microstructure.

Main Methods:

• Application of the short-time partial austenitization (SPA) process.
• Microstructural characterization of ferrite, reversed austenite (RA), and secondary martensite (SM).
• Analysis of (V, Mo)C precipitate morphology evolution during intercritical tempering and SPA.

Main Results:

• The SPA process transformed the microstructure from dual-phase ferrite and RA to a multiphase structure including ferrite, RA, and SM.
• The morphology of (V, Mo)C precipitates changed from disclike to near-spherical.
• A hierarchical microstructure with distinct layers (ferrite, SM, RA) resulted in a yield strength of 1097 MPa, 14% total elongation, and 33.3 J impact energy at -20 °C.
• (V, Mo)C precipitation contributed approximately 108 MPa to the overall strength.

Conclusions:

• The SPA process is effective in creating a multiphase hierarchical microstructure in V/Mo-bearing steel.
• This microstructure enables excellent combination of high yield strength and low-temperature toughness.
• The optimized precipitate morphology and hierarchical structure are key to the enhanced mechanical performance.