An Artificial Neural Network Model to Predict the Bainite Plate Thickness of Nanostructured Bainitic Steels Using an Efficient Network-Learning Algorithm

摘要

Nanostructured bainitic steel has an extraordinary ultrahigh strength of about 2.0GPa along with good toughness of 30MPam(1/2). The finer thickness of plate20-80nm is largely responsible for achieving such a large hardness of 690-720HV. In this work, a multilayer perceptron-based artificial neural network (ANN) model has been developed to predict the thickness of bainite plate pertaining to nanostructured bainitic steels. The inputs of the ANN model are, namely, Gibbs free energy for bainitic transformation, austenite strength, transformation temperature for bainite and carbon concentration in the steel. The model prediction revealed that the bainite plate thickness critically depends on austenite strength and Gibbs free energy. From the neural prediction, it is concluded that formation of nanostructured bainitic steel is feasible only if sufficient austenite strength (above 165MPa) has been achieved. This can be accomplished with a minimum carbon content of 0.5wt.% in steel and transformation temperature below 300 degrees C. Higher driving force (Gibbs free energy) below -1800J/mol is another prerequisite condition of formation of nanostructured bainite steel. The network-learning architecture has been optimized using the Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm to minimize the network training error within eight training cycles. The algorithm facilitates a faster convergence of network training and testing errors.