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Description
The third generation of AHSSs (3rd Gen-AHSS) offers a good combination of strength and ductility due to the different micro-constituents inherited in the base material microstructure. However, the as-received material needs to be formed at high temperatures to form different parts in the body-in-white structure (BIW). Forming at high temperatures is crucial to reduce the press tonnage requirements; however, that could impose phase transformation of the final product, which will result in different microstructure and, therefore, changes in mechanical properties (strength, bendability, and ductility). This work developed a quenching and partitioning (Q&P) intercritical heat treatment process to maintain the as-received third-generation advanced high-strength steel (3rd Gen-AHSS) microstructure. The influence of peak temperature, holding time at peak temperature, heating rate, quenching temperature, and partitioning temperature was investigated using a thermo-mechanical simulator system (Gleeble3500). Large enough coupons were heat treated using the thermal simulator, and the microstructure and mechanical testing results were compared with the as-received material. The yield strength, total elongation, and V-bend angle exceeded the as-received material properties, while the ultimate tensile strength was slightly lower than the as-received material by 9%.