By means of thermodynamic calculations, optical microscope, sweep electron microscope(SEM), transimssion electron microscope(TEM) and microcomposition detection, the modifying effect of RE and Ti on austenitic mangane...By means of thermodynamic calculations, optical microscope, sweep electron microscope(SEM), transimssion electron microscope(TEM) and microcomposition detection, the modifying effect of RE and Ti on austenitic manganese steel was investigated The results show that the constitutional supercooling of austenitic manganese steel during solidification can be improved and the dendritic crystals can be grown facilely, melted, isolated and multiplied by adding RE(Ce) In the melt the alloying elements Ti and C can form TiC directly which acts as nucleus of cementite and causes both primary and eutectic cementite to be granulated and refined so that the cementite network in this steel can be eliminated展开更多
The microstructures and mechanics properties of TiC-based cermets composed of TiC, WC, Ni, Co, Mo, and Cr3C2 were investigated. The results show that Mo has a great effect on the sintering densification, microstructur...The microstructures and mechanics properties of TiC-based cermets composed of TiC, WC, Ni, Co, Mo, and Cr3C2 were investigated. The results show that Mo has a great effect on the sintering densification, microstructures, and mechanical properties. The microstructures and distribution of Mo and Ti in the TiC-based cermets were analyzed. It was indicated that a new phase with Ti, Mo, W, and C was formed on the rim of （Ti,W）C grains by means of an addition of Mo into the TiC-based cermets. The new phase with a surrounding structure was of great aid to improve the wettability of the liquid phase on the solid phase surface of TiC, decrease the porosity and refine the grains of the hard phase, which gave rise to the increase in strength and hardness. The properties of the TiC-based cermets could be further improved to some extent by adding WC, Cr2C3, and Co.展开更多
The nanohardness H of multilayer specimens TiC/VC@Si and TiC/VC@Sapphire prepared by Pulsed-Laser-Deposition is investigated to check the existence of a superlattice effect as known from TiN/VN multilayers. In the pre...The nanohardness H of multilayer specimens TiC/VC@Si and TiC/VC@Sapphire prepared by Pulsed-Laser-Deposition is investigated to check the existence of a superlattice effect as known from TiN/VN multilayers. In the present work the multilayer period thickness λ varies between 1.34 nm and 24.8 nm (total layer thickness t ≈ 200 nm). Unlike Young’s modulus E, H is enhanced, regardless of t, by covering Si as well as sapphire with a TiC/VC multilayer;the relative load carrying capacity being larger for Si. The maximum value of H obtained is 38 GPa for TiC/VC@Sapphire. It is observed for a multilayer thickness of λ ≈ 10 nm. Hardness of TiC/VC@Sapphire obeys, after annealing, a Hall-Petch relation H = 35.25 + 6.945 λ–0.5 (H in GPa und λ≥ 10 nm). From orientation dependent X-ray absorption fine structure and X-ray reflection records, short-range order and layer geometry are derived. These analyses reveal a continuous approach of interatomic distances Ti-C and V-C for deceasing multilayer periods. High-resolution transmission electron microscopy shows that multilayers are nanostructured, i.e., not only TiC/VC phase boundaries but also subgrains represent obstacles against plastic deformation. Dislocations play a major role as sources of internal stress and vehicles of plasticity.展开更多
文摘By means of thermodynamic calculations, optical microscope, sweep electron microscope(SEM), transimssion electron microscope(TEM) and microcomposition detection, the modifying effect of RE and Ti on austenitic manganese steel was investigated The results show that the constitutional supercooling of austenitic manganese steel during solidification can be improved and the dendritic crystals can be grown facilely, melted, isolated and multiplied by adding RE(Ce) In the melt the alloying elements Ti and C can form TiC directly which acts as nucleus of cementite and causes both primary and eutectic cementite to be granulated and refined so that the cementite network in this steel can be eliminated
文摘The microstructures and mechanics properties of TiC-based cermets composed of TiC, WC, Ni, Co, Mo, and Cr3C2 were investigated. The results show that Mo has a great effect on the sintering densification, microstructures, and mechanical properties. The microstructures and distribution of Mo and Ti in the TiC-based cermets were analyzed. It was indicated that a new phase with Ti, Mo, W, and C was formed on the rim of （Ti,W）C grains by means of an addition of Mo into the TiC-based cermets. The new phase with a surrounding structure was of great aid to improve the wettability of the liquid phase on the solid phase surface of TiC, decrease the porosity and refine the grains of the hard phase, which gave rise to the increase in strength and hardness. The properties of the TiC-based cermets could be further improved to some extent by adding WC, Cr2C3, and Co.
基金thank the German Research Foundation(DFG)for financial support
文摘The nanohardness H of multilayer specimens TiC/VC@Si and TiC/VC@Sapphire prepared by Pulsed-Laser-Deposition is investigated to check the existence of a superlattice effect as known from TiN/VN multilayers. In the present work the multilayer period thickness λ varies between 1.34 nm and 24.8 nm (total layer thickness t ≈ 200 nm). Unlike Young’s modulus E, H is enhanced, regardless of t, by covering Si as well as sapphire with a TiC/VC multilayer;the relative load carrying capacity being larger for Si. The maximum value of H obtained is 38 GPa for TiC/VC@Sapphire. It is observed for a multilayer thickness of λ ≈ 10 nm. Hardness of TiC/VC@Sapphire obeys, after annealing, a Hall-Petch relation H = 35.25 + 6.945 λ–0.5 (H in GPa und λ≥ 10 nm). From orientation dependent X-ray absorption fine structure and X-ray reflection records, short-range order and layer geometry are derived. These analyses reveal a continuous approach of interatomic distances Ti-C and V-C for deceasing multilayer periods. High-resolution transmission electron microscopy shows that multilayers are nanostructured, i.e., not only TiC/VC phase boundaries but also subgrains represent obstacles against plastic deformation. Dislocations play a major role as sources of internal stress and vehicles of plasticity.
