Study of Elastic Behavior of Alloyed Steel upon Cyclic Loading

To study the mechanical properties and elastic behaviour of Q&P steel, which is a type of advanced high strength steel, uniaxial tension and cyclic loading tests have been conducted. Scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD) tests have been conducted on deformed samples with different degrees of deformation to analyse the microscopic mechanisms of their change in elastic modulus. The results have been shown a significant growth in the elastic modulus of alloyed steel after the initial unloading, followed by a decrease in the elastic modulus with the increase in the degree of unloading. The unloading and reloading paths showed a clear nonlinearity and formed a closed loop. The unloading chord modulus also decreased gradually with the increase in a pre-strain. The results of SEM, TEM, and XRD have been shown that the phase transformation variation is the strongest during the early stage of plastic deformation, and then gradually decreases. Cyclic loading has promoted the transformation from austenite to martensite. Interactions of the residual stress, phase transformation, and dislocation movement affecting the change in elastic modulus are determined through this research.