OPTIMIZATION OF COLD AND WARM WORKABILITY IN STAINLESS-STEEL TYPE AISI 316L USING INSTABILITY MAPS

The deformation characteristics of stainless steel type AISI 316L unde r compression in the temperature range 20 to 600 degrees C and strain rate range 0.001 to 100 s(-1) have been studied with a view to charact erizing the flow instabilities occurring in the microstructure. At tem peratures lower than 100 degrees C and strain rates higher than 0.1 s( -1), 316L stainless steel exhibits flow localization whereas dynamic s train aging (DSA) occurs at intermediate temperatures and below 1 s(-1 ). To avoid the above flow instabilities, cold working should be carri ed out at strain rates less than 0.1 s(-1). Warm working of stainless steel type AISI 316L may be done in the temperature and strain rate re gime of: 300 to 400 degrees C and 0.001 s(-1) 300 to 450 degrees C and 0.01 s(-1): 450 to 600 degrees C and 0.1 s(-1); 500 degrees C and 1 s (-1) since these regions are free from flow instabilities like DSA and flow localization. The continuum criterion, developed on the basis of the principles of maximum rate of entropy production and separability of the dissipation function, predicts accurately all the above instab ility features.