Optimization of process parameters using the Grey-Taguchi method and experimental validation in TRIP-assisted steel

Intercritical annealing, quenching, and partitioning (I&Q&P) parameters of transformation-induced plasticity (TRIP)-assisted steel were optimized using the Grey-Taguchi method. The optimum combination of mechanical properties was achieved after nine sets of experiments based on an orthogonal array. The influence of each factor was investigated based on the grey relational analysis, and the results indicated that quenching temperature had the most significant effect on the mechanical properties, followed by partitioning temperature and partitioning time. The stability of retained austenite (RA) and the strain hardening behavior during deformation were investigated to determine the origin of the best and worst mechanical properties from the orthogonal experiments. For the best mechanical properties, the stability of RA is the highest, and the TRIP effect occurs in almost all uniform deformation stages, benefiting from RA having various locations, morphologies, grain sizes, and orientation relationships with adjacent phases. For the worst mechanical properties, a large amount of TiC precipitation occurs, which consumes a portion of the carbon atoms partitioning from the supersaturated martensite to austenite, resulting in the lowest carbon content and stability of RA. The findings can provide a new method for accurately and effectively optimizing the processing parameters and analyzing their influence on mechanical properties.