Strain Rate Effects on the Elevated-Temperature Tensile Behavior of a Bainitic 2-1/4 Cr-1 Mo Steel

Abstract

The tensile properties of a normalized-and-tempered 2-1/4 Cr-1 Mo steel were determined from 25 to 566° C and the strain rate 2.67 × 10−6 to 144/s. The specimens were taken from a 1-in. thick plate and had a microstructure that was essentially 100 percent bainite. Except at 25 and 566° C, the 0.2 percent yield stress was little affected by strain rate; at 25 and 566° C, the yield stress increased with increasing strain rate. At a constant strain rate, the yield stress decreased with increasing temperature. The effect of strain rate and temperature on the ultimate tensile strength was somewhat more complicated. A strength peak that resulted from dynamic strain aging was observed in the ultimate tensile strength-temperature relationship. The position of these peaks moved to higher temperatures with increasing strain rate. Total elongation and reduction of area were relatively constant over the range of test variables, except at 566° C, where they increased with decreasing strain rate. However, uniform elongation decreased with decreasing strain rate at 510 and 566° C, dropping to 1 and 0.6 percent, respectively.