Quantitative Analysis of Retained Austenite in Nb Added Fe-based Alloy

Abstract

Use of Pipe lines for long-distance transportation of crude oil, natural gas etc., increasing and have pivotal importance in recent times. To improve transport efficiency through increased pressure and improved laying efficiency through reduced diameter and weight of line pipes, high specific strength plays a crucial role. TRIP-based high-strength and high-ductility alloys comprise a mixture of ferrite, bainite, and retained austenite that provide excellent mechanical properties such as dimensional stability, fatigue strength, and impact toughness. In this study, microstructure analysis performs using both Nital etching and LePera etching methods. At the time of Nital etching, it is difficult to distinctly observe second phase. However, using LePera etching conditions it is possible to distinctly measure M / A phase and ferrite matrix. The fraction measurement was done using OM and SEM images which gives similar results for the average volume fraction. Although it is possible to distinguish the M / A phase from the SEM image of the sample subjected to LePera etching, but using Nital etching it is impossible. Nital etching is good at specific phase analysis than LePera etching through the SEM images.