Significance of Mn concentration on aging behavior, microstructure evolution and mechanical properties of Fe–Ni–Mn alloys

Abstract

Fe–Ni–Mn alloys, are ultra-high-strength steels, with suitable ductility and age-hardenability in the solution annealed (SA) condition. However, they suffer from grain boundary embrittlement after aging at ∼480OC, when Mn content goes beyond a specific value. This study was conducted to investigate systematically the effects of the Mn concentration on the microstructural evolution, aging behavior, and the resulting mechanical properties of Fe–10Ni–xMn alloys containing 3.5, 6 and 9Mn wt.%. Samples containing 3.5 and 6 wt.% Mn showed age-hardenability during aging and higher Mn content resulted in a higher hardness value which in turn showed higher strength. The Mn content of about 9 wt.% led to the stability of the austenite phase at room temperature (RT). The results showed that although age-hardening did not occur in this microstructure, a good combination of strength and ductility was achieved. Studying the effects of Mn content in a wide range, resulted in different properties by introducing the proper chemical composition and the preferred heat treatments in this type of alloys, which could be age-hardenable, easy to fabricate, and low-cost.

Keywords

• Martensitic steel
• Precipitation
• Age-hardenability
• Mechanical properties