Neural Network Approach to Construct a Processing Map from a Non-linear Stress-Temperature Relationship

Abstract

An accurate processing map for a metal provides a means of attaining a desired microstructure and required shape through thermo-mechanical processing. To construct such a map, the isothermal flow stress, sigma(iso), is required. Conventionally, the non-isothermal flow stress measured by experiment is corrected to sigma(iso) using whole-temperature-range linear interpolation (WRLI) or partial-temperature-range linear interpolation (PRLI). However, these approaches could incur significant errors if the non-isothermal flow stress exhibits a non-linear relationship with the temperature. In this study, an artificial neural network (ANN) model was applied to correct the non-isothermal flow stress in 10 wt% Cr steel, which exhibits a non-linear temperature dependence within a target temperature range of 750-1250 degrees C. Processing maps were constructed using sigma(iso) corrected by applying the WRLI, PRLI, and ANN approaches, respectively, and were then compared with the actual microstructures. The WRLI approach produced the highest minimum error of sigma(iso) (17.2%) and over-predicted the shear-band formation. The PRLI approach reasonably predicted the microstructural changes, but the minimum error for sigma(iso) (8.9%) was somewhat high. The ANN approach not only realized the lowest minimum error of sigma(iso) (similar to 0%), but also effectively predicted the microstructural changes.