Investigation of Plastic Behavior of Alloyed Steel Deformed During Martensitic Transformation

We present the investigation of permanent strain of steel specimen occurred when metallurgical transformations take place even under small stress applied externally lower than the yield stress of material. Three alloyed steel grades were investigated: THG2000 (Uddeholm, Sweden), 40Kh13 and 95Kh18 (GOST, Russia). All steel grades differ in carbon content and amount of alloying elements and behave differently when transformation occurs. This intensively increased plasticity of steel specimen was observed during bending test when bending stress was just 100 MPa and was less than 10% of yield strength of the steel. The steel specimens were heated to 900–1050°C temperature and then bent during air quenching. Plastic deflections were observed though all cooling process that involved martensitic transformation as well. Different effect of compression and tensile stresses on microstructure evolution during martensitic transformation was determined by X-ray analysis as both types of stresses were formed in bent specimens.