Study On Mechanical Behavior Of Cu-P-Cr-Ni-Mo Dual Phase Steel Based On ANSYS

Dual phase steels consist of microstructure of soft ferrite matrix and martensite,which is an ideal structure material for locomotive industry due to their combination of high strength and ductility,and formability.The dual phase steels in the paper with different martensite content and different martensite morphologies were produced by heat treatment and hot rolling respectively.The plastic deformability and fracture behavior of dual phase steels not only depends on the properties of martensite and ferrite but also on the content and morphology of the martensite.The microstructure of dual phase steels was observed to be inhomogeneous,the properties of ferrite is greatly different from that of martensite,and each grain orientation within every phase are also different,so it's difficult to capture the crack propagation and distribution of stress-strain among dual phase steels.A microstructure based 2D geometry model was developed in CAD,and the isotropic model and multi-linear kinematic hardening model were also established.Finite element simulations were conducted in ANSYS to explore the elastic-plastic behavior,void formation method and fracture procedure.The stress-strain curves obtained from tests correlates well with that of simulated,which indicate that the finite element model is effective and correct.The results of simulation illustrated that the ferrite bearing strain,multiple bands in 45? or-45? to tensile direction were formed,which linked and developed through the whole steel.For the dual phase steels with different martensite morphology: the local stress concentration mainly occurred in the inner part of martensite,partly near the phase boundaries,the plastic strain localization takes place in areas characterized by high density of martensite.The local stress concentration in the dual phase steels with fibrous martensite is more serious;For the dual phase steels with different martensite content,stress concentration is proportional to the martensite content,and are more likely to located near the interface,partly in the inner of martensite.The SEM observation of the necking zone show that: For the dual phase steels with island,columnar and fibrous martensite,the void nucleation mainly takes place by the cracking of martensite,and partly due to the decohesion of interface between the ferrite matrix and the martensite.The more length the martensite is,the more sites were provided for the voids nucleation.The dual phase steels with higher content of martensite improved the nucleate probability of void,the cracks propagation along phase boundaries.The probability of encountering martensite is increased in the process of crack growth.Finally,the behavior of void nucleation and coalecence resulted in the fracture of dual phase steels.The results of tensile testes are in good agreement with the simulation of dual-phase steels,which verifies the correct and validity of the numerical simulate.