Experimental Investigation To Study the Effect of Heat Treatment on Mechanical Properties and Microstructure of Duplex Stainless Steel

Abstract

The broad aim of this paper is to study the enhancement in mechanical properties of duplex steel by thermomechanical processing. Solution annealing followed by water quenching, hot rolling to 10% and 30%, cryo-rolling to 80% and 90% and ageing at 600°C and 1000°C for 5 hrs were the treatments given. The cryo-rolled samples were used for impact testing and rest for tensile testing. Microstructural analysis was done after the various treatments, and the volume fraction was seen to decrease with increase in temperature. Young's modulus (YM) for a particular mechanical treatment does not changes with temperature and it increases with decreasing rolling %; Yield Strength (YS) being least for annealed samples, intermediate for rolled samples heated at 1000°C and maximum for rolled samples heated at 600°C, and it increases with increasing the rolling percentage; Ultimate tensile strength (UTS) gain is least for Simulated annealing (SA) samples, maximum for rolled samples heated at 600°C and a little less for those heated at 1000°C. Toughness calculated from the area under the stress-strain curves obtained from the tensile data has been compared with the impact energy values from the impact test. Impact energy showed an increasing trend with temperature as expected, but toughness values did not show such a trend. Fractal analysis was performed for the fractured surfaces obtained from tensile tests to characterize the fracture and to correlate it with the material’s properties.