Research On Carbide Precipitation Behavior And Mechanical Properties Of Fe-0.88 C-17Mn Steel Under Aging Treatment

High-manganese steels are widely used for wear-resistant parts because of its excellent work-hardening ability under high impact loads.However,traditional high-manganese steels may not be able to obtain high wear-resistance due to low initial hardness and yield strength,which caused by insufficient work-hardening under the initial use or low-impact stress conditions.In this study,Fe-0.88C-17Mn high manganese steels were treated with different aging temperatures and times,and the changes of carbide precipitation behavior and mechanical properties after aging treatment were investigated by Metallographic(OM),Scanning electron microscopy(SEM),Electronic parts manufacturers association(EPMA),Transmission electron microscopy(TEM)and Nanoindentation methods,while the wear properties and mechanisms of high-manganese steel treated with different aging temperatures and times were studied by impact abrasive wear tests.The wear properties and mechanisms of high-manganese steel with different aging treatments were also investigated by impact abrasive wear tests.The main results of the study are as follows:(1)After aging treatment,carbides precipitate from the matrix of high-manganese steel.The temperature and time of aging treatment were the main factors that determined the number,size and dispersion degree of carbides.With the increase of aging temperature,the micro-sized carbides in the matrix coarsened obviously.However,as the aging time extended at 400?,the micro-sized carbides in the test steel did not coarsen significantly and were more uniformly distributed.The size,volume fraction and dispersion of submicron and nano-sized V₂C particles increased with the increase of aging temperature and aging time,while the untempered high-manganese steel(UT)contained almost no nano-sized V₂C particles.The carbide of high-manganese steel achieved the best precipitation and dispersion at 400°C for 24 h treatment(AT24).(2)With the increase of aging temperature,the strength and work-hardening capacity of high manganese steel were improved obviously.The yield strength of500T steel was 537 MPa,which was increased by 91 MPa compared with UT steel.Meanwhile,the nano-hardness of UT,400T,450T and 500T steel are 7.67 GPa,8.82 GPa,9.96 GPa and 12.33 GPa,respectively,and the Young's modulus was 235GPa,240.5 GPa,255.7 GPa and 290.6 GPa,respectively.The thickness of the work-hardening layer of 500T steel was about 3900?m,which was 2.5 times that of UT steel,and the work-hardening index was 0.643.The yield strength of AT24steel was 548 MPa as the increasing of aging time,while the work-hardening rate reached an ultra-high level of about 75 GPa,which indicated the outstanding of work-hardening sensitivity ability.The nano-hardness and Young's modulus of AT24 steel were 16.86 GPa and 370 GPa,respectively.The increment of precipitation strengthening of high-manganese steel increased as the aging temperature and time increasing,and the increment of precipitation strengthening of 500T and AT24 steel were 198.05 MPa and 277.9 MPa,respectively.The aging time treatment exhibited better strengthening effect than temperature.(3)The wear-resistance of high-manganese steel increased with increasing aging temperature and time.In the initial stage of impact abrasive wear,the aging temperature treated specimens shown better wear performance relative to time.It was due to the larger size of micro-sized carbides in the matrix of the aging temperature treated specimens,and the micro-sized carbides with extremely high hardness attach to the wear surface to enhance the matrix's ability to resist micro-cutting.During the impact wear progresses,sufficient impact energy accumulates on the surface of the specimens,resulting in work-hardening.Meanwhile,the wear loss advantage of the specimens treated with aging temperature decreases,and the AT24 steel obtains the best mechanical properties and wear-resistance.This is because the specimens treated with aging time had better precipitation behavior and precipitation strengthening increment,thus showing better work-hardening ability(high hardness and high yield strength),which greatly improved the impact wear performance of the steels.(4)Micro-sized carbides can improve the wear-resistance of high-manganese steel by resisting the micro-cutting by hard abrasive particles.Due to the lack of work-hardening on the surface of high manganese steel at the early wear stage,the hardness and yield strength of austenite matrix are low,which does not support the micro-sized carbides sufficient,resulting in the carbides detaching from the wear surface and reducing the wear-resistance.The large number of nano-sized V₂C particles precipitated of high-manganese steel after aging treatment improves the yield strength of the austenite matrix by impeding the dislocation movement,which in turn provided stronger support to the micro-sized carbides,and ultimately enhanced the wear-resistance significantly.The wear mechanism of high-manganese steel changes from micro-cutting to plastic deformation.