A Study of Mechanical Properties and Weldability in Weldment of Cold-Rolled Fe-19Mn-5.5Cr-3.5Al-0.25C Alloy at Cryogenic Temperature

Abstract

This work is concerned with the mechanical properties and weldability of cold-rolled Fe-19Mn-5.5Cr-3.5A1-0.25C alloy for cryogenic use. The cold-rolled sheet was entirely recrystallized in annealing condition at 1173 K and exhibited good ductility at 1273 K. As decreasing tensile test temperature, the yield and tensile strength of the alloy annealed at 1273 K increased. However, the elongation did not change greatly. It was revealed that the high elongations of this alloy were caused by the formation of deformation twin at RT and deformation twin plus α′-martensite at 110 K.

The weldability and low temperature mechanical properties of the gas tungsten arc welding (GTAW) weldments for alloy annealed at 1273 K have been investigated. All weldments of this alloy were welded without hot cracking and HAZ micro-fissuring. The weld metals welded with and without filler metal by GTAW process showed the δ-ferrite that was formed during solidification. It was revealed that the δ-ferrite content slightly increased as increasing heat input. The hardness of weld metal was higher than that of base metal due to the formation of δ-ferrite. As the results of tensile tests of GTAW weldments, the yield and tensile strength were higher than those of base metal at RT and 110K. The elongations of GTAW weldments without filler metal and with filler metal were 49.9% and 41.7% at RT and 41.6% and 45.5% at 110 K, respectively.