Microstructure, Mechanical Behavior and Crystallographic Texture in a Hot Forged Dual Phase Stainless Steel.

Abstract

In this work, the hot forging behavior of a dual phase stainless steel in the temperature range of 850 – 1250 °C was investigated. The study revealed the occurrence of a significant cracking phenomenon for processing temperatures below 950 °C that was attributed to the combined effect of intermetallic precipitation and severe deformation. EBSD examination highlighted the occurrence of continuous dynamic recrystallization in both ferrite and austenite microstructures for processing temperatures above 1050 °C. Increasing the hot forging temperature to 1250 °C increased the low angle grain boundaries fraction and lowered the one of the high angle grain boundaries. This was accompanied by a gradual change in the crystallographic texture of the material. The mechanical behavior investigation showed that the steel plasticity, sharply dropped after forging at 850°, was gradually recovered after hot forging at temperatures above 1050°C. This was confirmed by nanoindentation measurements that revealed a remarkable increase of the hardness and young modulus of the steel after hot forging at 850°C and 950°C due to the dislocation nucleation and the s phase precipitation at g/δ interface. The enhancement of dislocation movement at the vicinity of the grain boundaries due to the absence of s phase as well as the dynamic recovery and recrystallization occurring in the temperature range of 1050°C - 1250 °C improved the global mechanical properties of the hot forged steel.