TENSILE, HIGH STRAIN RATE COMPRESSION AND MICROSTRUCTURAL EVALUATION OF LIGHTWEIGHT AGE HARDENABLE CAST FE-30MN-9AL-XSI-0.9C-0.5MO STEEL

摘要

Age hardenable, castable, and lightweight Fe-Mn-Al-C steels are currently being developed and evaluated for substitution of high strength low alloy steel and to meet MIL-PRF-32269 criteria. Two nominal Fe-30Mn-9Al-0.9C-0.5Mo steels were cast and modified with 1 and 1.4 wt.% silicon. Ageing, tensile, and high strain rate compression testing were performed on solution treated and aged samples of both chemistries. Each alloy was solution treated at 1050℃ for 2 hours. Microstructures of the solution treated and aged alloys show primary austenite with less than 8 volume% ferrite. The solution treated hardness of the low silicon steel was 230 BHN and the high silicon alloy was 225 BHN. Specimens were aged at 530℃ for up to 60 hours. Peak ageing occurs after 30 hours with a peak hardness of 371 BHN for the 1% silicon containing alloy and 377 BHN for the high silicon alloy. Tensile strengths of the 30 hour aged specimens were 1065 MPa (154 ksi) and 1080 MPa (156 ksi) for the low and high silicon alloys. High strain rate compression testing was conducted on solution treated and 10 hour aged 1% Si containing alloy. Compressive strength of the 1 wt.% Si alloy exceeded 1,500 MPa (217 ksi) at a strain rate of 3000 s.