The microstructure and mechanical properties of prolonged and lower temperature aged Fe-Ni-Mn-Mo-Ti-Cr maraging steel

Abstract

In this study, the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steel at low temperature and prolonged aging condition were investigated. Optical and scanning electron microscopy examinations, tensile and hardness tests were conducted to study the microstructure, aging behavior and mechanical properties of the cold-rolled steel. The results showed that aging of cold rolled Fe-Ni-Mn-Mo-Ti-Cr maraging steel resulted in the formation of Mo rich and Ti rich Lave phase precipitates. Existence of many dislocation cores due to cold rolling and subsequently, low temperature aging caused to formation of uniform distribution of very fine precipitates. The presence of these precipitates increased the yield and ultimate tensile strengths but couldn't improve the uniform tensile ductility. This alloy showed ultra-high fracture stress of about 1950 MPa with a negligible tensile elongation (about 2%) at the peak aged condition. The fractographic studies indicated this alloy shows semi-brittle fracture in the subsequent aging treatment.