中高碳纳米结构trip钢高速拉伸性能的研究材料学专业论文.docxVIP

AbstractThe Abstract The aim is to study the effect of different heat treatment processes on high speed tensile properties of medium-high carbon nanstructured TRIP steels in this paper Firstly，We investigated the microstructures and mechanical properties of the experimental steel with the multi-step low temperature bainitic transformation and the quenching and partitioning(QP)process．Secondly，the microstructures，phase fraction were analyzed by OM(optical microscopy)，SEM(scanning electron microscopy)，TEM(transmission electron microscopy)and XRD(X-ray diffraction)． The traditional tensile test was carried out and the micro．hardness was measured Finally,the high speed tensile properties of three—step low temperature bainitic transformation and quenching and partitioning(QP)process were studied under din-erent Strain rates．The main results are as follows 1．Compared with the tradkional one-step bainitic transformation，multi-step low temperature bainitic transformation effectively reduced the average thickness of bainite plates as well as the size and volume fraction of retained austenite，SO that the mechanical propeRies Can he greatly improved．The multi—step low temperature bainitic transformation can get a higher product of strength and ductility，which is close to(or higher than)that of quenching and partitioning process in traditional tensile test． 2．The microstuctures of multi-step low temperature bainitic transformation and quenching and partitioning process is similar，including nanostrcutured bainite·ferrite (or martensite)plates and retained austenite．Both of them have a higher volume l置action of retained austenite and micro．hardness 3．The fracture mode of multi—step low temperature bainitic transformation and quenching and partitioning process is ductile l}acture．Many dimples with different sizes in the fracture surfaces were observed by SEM microscope 4．In the high speed tensile tests．the three-step low temperature bainitic 万方数据 transformation transformation o