| The practice has shown that the work hardening degree of high manganese is inconspicuous in the low impact load working conditions,which induced the poor wear-resistance performance.Therefore,the medium manganese steel has been researched a lot both at home and abroad,in order to decrease the stability of austenite,the volume of manganese in the steel has been reduced.In this paper,we have researched wear-resistance performance and work hardening mechanism under different conditions of the BTW（deformation induced hardening austenitic medium manganese steel）,and used XRD,SEM,TEM,EBSD,etc to research the work hardening mechanism and work hardening performance.And this paper will provide the theoretical foundation for the using and popularizing in mine industry.The conclusions in this paper are stated as follows.In the impact abrasion tests,with increasing of the accumulated impact energy,the dislocation density of BTW worn surface increases and mass dislocations are snarling with each other and forming the dislocation islands.Worn surface damage mechanism of BTW changes from plough and cut to the cut and fatigue flake;at the same time,the amount of martensite remains around 35%.BTW has the largest degree of strain hardening when impact energy approach 3.5 J,and it has the best wear-resistance performance at same time.So the critical impact energy is 3.5 J.The change law between the stack fault energy and strain rate of high strain rate and strain dynamic compression test is that the stack fault energy links with strain positively and goes up in proportion to the increase of strain rate and temperature.The largest stack fault energy is beyond 202mJ/m2 in the compression test.The deformation mechanism is strain induced martensitic phase transformation and dislocations slip,and there is no twins,which indicates the stack fault energy is not applicable for the predication of deformation mechanism of austenitic medium manganese steel.The research of the work hardening performance and work hardening mechanism shows that BTW is the strain rate sensible materials.The ultimate strength is sensible to the strain rate,and the yield strength is not sensible to the strain rate.Variation of work hardening index n of BTW which show the multiplicity at the tensile process,and exists the phenomena that large grain boundary angle changes to small grain boundary angle.The BTW has different work hardening mechanism in the different conditions:in the low strength and low strain rate,it is the strain induced twin reinforcement and dynamic aging strengthening;in the high rate and high strength dynamic compression conditions,it is the deformation induced martensite phase transformation strengthening and high density dislocation strengthening;in the complete conditions such as impact abrasion wear test,it is the strain induced twin reinforcement,martensite phase transformation strengthening,dislocations and stack fault strengtheningThe martensitic phase transformation in BTW is mainly theεandαmartensite.Theεandαmartensite nucleation is mainly in the dislocations and stack fault which accord with the regular that the phase transformation mainly occurs in crystal defect.The theoretical calculation of critical nucleation size is 27.1nm,the critical nucleation energy is 41.2J/mol;in the impact abrasion wear test,the shear angle ofγ→εis 19.4°,which accord with the theoretical angle,this indicates that the BTW martensite phase transformation is conform to the shear mechanism.The deformation pattern of BTW in different conditions is mainly phrase transformation,dislocation slip and twins;the structure of BTW in the deformation process includes high density dislocation,stack fault,twins,αandεmartensite.The substructure of deformation induced martensite is high density dislocations,dislocation cells and dislocation entanglements. |
