Influence of strain rate and temperature on tensile properties of 9Cr-1Mo ferritic steel

Tensile tests were performed on specimens in the normalised and tempered condition to assess the effects of temperature (300 - 873 K) and strain rate (6.33 x 10(-5) -6.33 x 10(-3) s(-1)) on tensile deformation and fracture behaviour of 9Cr - 1Mo ferritic steel. At all strain rates, the yield and ultimate tensile strength values exhibited a gradual decrease up to intermediate temperatures followed by a rapid decrease at high temperatures. Elongation to fracture and reduction in area displayed a gradual decrease to a minimum at intermediate temperatures followed by a rapid increase at high temperatures. At intermediate temperatures, 9Cr - 1Mo steel exhibited serrated flow, plateaus and peaks in strength values and work hardening rate, and negative strain rate sensitivity. The activation energy estimated from the strain to onset of serrations indicated diffusion of interstitial solutes such as carbon responsible for serrated flow in 9Cr - 1Mo steel. At high temperatures, a systematic decrease in yield and tensile strength values with decreasing strain rate has been observed. The fracture mode remained transgranular.