Stability of retained austenite in quenched and partitioned steel wires

摘要

Steel wires having a microstructure containing martensite and retained austenite were produced with the quenching and partitioning (Q&P) thermal process. The Q&P wires exhibited high 'total elongation' x 'tensile strength' product, above 20000%N/mm~2. This product is two to three times higher than in wires processed with the more conventional quenching & tempering treatment. The higher elongation measured in Q&P wire was due to the TRIP (Transformation Induced Plasticity) effect during plastic deformation. Electron back scattering diffraction and magnetic saturation measurements combined with the results of the Koistinen-Marburger equation were used to characterize the microstructures. The stability of retained austenite was quantified by means of interrupted tensile and fatigue tests. The kinetics of carbon diffusion out of martensite to austenite has been studied to increase the stability of retained austenite and design a new family of products for e.g. applications where high energy absorption is required.