Warm Deformation Mechanism Of Cementite In Steel

In this paper, the dissolution and deformation mechanisms of cementite in T10steelundergoing warm deformation were investigated.At first, T10steel was annealed to obtain granular cementite particles. The sampleswere compressed with strains of10%,30%,50%and70%, at temperatures of200℃,350℃,500℃and650℃respectively. In this research, optical microscope (OM),scanning electron microscope (SEM) and transmission electron microscope (TEM)analyses were applied to count changes of average cementite particle size and latticedistortion of cementite before and after deformation. The stress state of cementite wasalso analyzed here. Besides, the influence of deformation temperatures on the activation ofslip systems in cementite was discussed. At last, the dissolution mechanism of cementiteundergoing warm deformation was studied.The results show that the average cementite particle size tends to decrease from0.83μm before deformation to about0.70μm after deformation at650℃. The latticeconstants of cementite decrease slightly from0.5352nm×0.46nm×0.6895nm to0.4948nm×0.4948nm×0.4579nm after compression deformation. Furthermore, moreslip systems are activated in cementite with increasing temperature. At temperatures of200℃and350℃, there is only one set of slip plane in cementite. However,(100) and (010)slip planes are observed at500℃and (100),(010) and (110) slip planes are activated indeformed cementite particles at650℃.The variations of average cementite particle size are different at differenttemperatures. Nevertheless, the particle size changes small at650℃with all kinds ofdeformation strain, this indicates that cementite particles decompose during isothermalholding at this temperature and plastic deformation accelerates this process.When the compressive force acting on the lattice of cementite exceeds its elastic limit,irreversible shrinkage occurs, leading to a slight lattice constant decrease of cementite. AsFe-C covalent bonding strength and other forces diminish due to the relative hightemperature, multiple slip systems are more likely to be activated under stress.