Effect of Mg content on the hot ductility of wrought Fe-36Ni alloy with Ti addition

Abstract

Austenitic alloys are prone to cracking as a result of their poor hot ductility during continuous casting and hot working processes. In this study, hot tensile tests were performed to study the effect of Mg content on the hot ductility of Fe-36Ni alloy over the temperature range of 700–1200°C at a strain rate of 10−2s−1. The effects of the Mg content on the particle (i.e., inclusion and precipitate) characteristics and the growth of austenite grains were also investigated. The results indicated that the number density of the particles increased significantly while the mean diameter decreased with increasing Mg content in the experimental alloys. The growth of austenite grains was effectively inhibited by pinning particles in the Mg-treated alloys during solution treatment. Both the pinning particle and austenite grain size markedly affected the hot ductility behaviors of the alloys. The hot ductility curves of the studied alloys had different trends in the intermediate temperature range and were controlled by the competition between dynamic recrystallization (DRX) and grain boundary sliding (GBS). Compared with the alloys without Mg addition, an appropriate number of pinning particles in the alloy with 49ppm Mg addition resulted in a smaller grain size during the solution treatment, which significantly improved the hot ductility by accelerating DRX during the subsequent hot tensile process. However, an excessive number of pinning particles at grain boundaries in the alloy with 60ppm Mg addition inhibited DRX and promoted GBS during the hot tensile process, which were detrimental to the hot ductility. In contrast, the alloys exhibited similar hot ductility troughs at higher temperatures, indicating that Mg has only a slight effect on the hot ductility at these temperatures.