Effect of reverted austenite on mechanical properties of precipitation hardenable 17-4 stainlesssteel

Precipitation hardenable 17-4 stainless steel has been subjected to a solution annealing treatment followed by ageing treatment at 580 °C for durations upto 6 h. Microstructural characterization of the solution annealed and the aged specimens has been done using optical microscopy, X-ray diffraction and electron backscattered diffraction. Mechanical characterization was done using tensile testing and charpy impact toughness testing at room temperature. Microstructural characterization indicated that the reverted austenite formation started in the initial stages of the ageing treatment itself and it continuously increased with duration of ageing. Results of mechanical testing indicated that the austenite content did not correlate with the strength of the material therefore, nature of the copper precipitates, which form along with the reverted austenite, is the dominant factor controlling the strength and the impact properties.