Tensile properties and prediction of DP780 treated with rare earth Ce based on DE-SVM-Ⅱ

Abstract

In order to solve the weak tensile properties of DP780 welded joints, rare earth Ce was added to improve the tensile properties of DP780 welded joints. In this paper, the microstructure of DP780 was characterized by metallographic microscopy, scanning electron microscopy and energy spectrum analyzer. An improved differential evolution algorithm optimized support vector machine prediction model (DE-SVM-II) was established to predict the tensile properties of DP780. The results show that when the content of Ce was 0.05%, the tensile strength increased by 378 MPa, the microstructure of molten metal was uniform and the grain boundary of austenite was tight. In the heat affected zone, the size of ferrite decreases, the fracture morphology shows equiaxial depression, and the fiber zone accounts for a large proportion. In addition, the fitness of the mean square error (MSE) of the tensile strength curve in the DE-SVM-Ⅱ prediction was lower than that of the SVM prediction error, and begin to converge in the 10th generation. The average relative error of the DE-SVM model prediction of elongation was within 3%. Compared with the predicted value of BP neural network, the error of predicting tensile strength and elongation of DE-SVM-II was reduced by 1.36% and 15.10%, respectively, which had high stability and accuracy.