EFFECT OF TEMPERATURE AND STRAIN-RATE ON TENSILE BEHAVIOR OF M250 MARAGING-STEEL

The effect of temperature and strain rate on the 0.2% yield strength, ultimate tensile strength, and percentage elongation of M250 maraging steel was investigated under uniaxial tensile conditions in the temper ature range from 25 (room temperature) to 550 degrees C and strain rat e range 10(-4)-10(-1) s(-1). Up to 400 degrees C the steel shows essen tially strain rate insensitive behaviour with a gradual decrease in th e 0.2% yield strength and ultimate tensile strength. The elongation re mains constant at all strain rates up to 300 degrees C. Fractographic analysis indicates that the increasing strain rate induces strain cons traint resulting in an increased dimple size. An elongated structure w as observed at temperatures above 400 degrees C. X-ray diffraction rev eals the presence of reverted austenite in the specimens tested at 550 degrees C. (C) 1996 The Institute of Materials.