Comparative study of tensile flow parameters in forged and rolled 9Cr-1Mo steel

Abstract

Tensile tests were carried out on a 9Cr-1Mo steel forging and a rolled plate in the temperature range 300-873 K at a nominal strain rate of 3 × 10^-4 s^-1. A comparative evaluation of tensile flow parameters of these materials has been performed. The Holloman equation was found to describe true-stress-strain data only at temperatures above 673 K, while at lower temperatures Ludwigson's modification of Holloman's equation was found to describe the flow curves for both the materials. The Ludwigson and Holloman parameters showed plateaux in the intermediate temperature range where serrated flow was observed in the load/elongation curve. Thick section forging exhibited a higher strain hardening exponent than that of a rolled plate. This has been attributed to the higher interbarrier distance in forged material.