COMPUTER MODELING FOR THE YIELD STRENGTH OF THE MIXED MICROSTRUCTURESBAINITE AND MARTENSITE

The strength of mixed microstructures of bainite and martensite can pe ak at an intermediate volume fraction of martensite has been published by recently experimental studies. A quantitative interpretation of th ese observations is achieved by modelling the mechanical properties of mixed microstructures of bainite and martensite. The peak in the curv e of the strength as a function of the volume fraction of martensite c an be attributed to two factors. It enriches the residual austenite wi th carbon when bainite forms, so that the strength of the subsequent m artensite increases. In addition, the strength of the bainite is enhan ced via plastic constraint by the surrounding stronger martensite. Thi s means the bainite is under a tri-axial stress state. Taking these ef fects into consideration for the computer modelling, it is possible to predict accurately both the trends and the absolute values of publish ed experimental data on the strength of mixed microstructures.