Composites of NiTi2-TiB have been fabricated using spark plasma sintering and mechanical properties have been investigated. Dense specimens of monolithic NiTi2 have been obtained by the sintering at 950?C. By the x-ra...Composites of NiTi2-TiB have been fabricated using spark plasma sintering and mechanical properties have been investigated. Dense specimens of monolithic NiTi2 have been obtained by the sintering at 950?C. By the x-ray diffraction measurements it has been shown that NiTi2 co-exists with TiB in equilibrium at 950?C. The bending strength of NiTi2-TiB composite increases with increasing the volume fraction of TiB2 up to 60 vol%. The maximum bending strength of 730 MPa has been obtained for NiTi2-60vol% TiB2. The Vickers hardness also increases with increasing the volume fraction of TiB up to 70% and the highest Vickers hardness of 1620 Hv has been obtained for NiTi2-70%TiB.展开更多
Ti-Ni-Mo-Si composite coating was fabricated on mild steel by reactive braze coating process with Ti61. 9Ni24. 6Si4. 411409.1 （ wt. % ） powders as the raw materials. Microstr^cture of the coating was characterized b...Ti-Ni-Mo-Si composite coating was fabricated on mild steel by reactive braze coating process with Ti61. 9Ni24. 6Si4. 411409.1 （ wt. % ） powders as the raw materials. Microstr^cture of the coating was characterized by optical microscopy, scanning electron microscopy, X-ray diffraction and energy dispersive spectroscopy and micro-hardness tester. Results indicate that the Ti-Ni-Mo-Si composite coating is metallurgically bonded to the mild steel substrate and has high hardness. The microstructure of the coating consists of the reinforcement of Ti5 Si3 and Mo9 Ti4 particles and the matrix of eutectic NiTi2. Due to the poor wettability of NiTi2 liquid at low temperature, TisSi3 and Mo9 Ti4 do not uniformly distribute in the NiTi2 matrix.展开更多
We employ density functional theory to study the mechanical, electronic and thermodynamic properties of the cubic NiTi in a prssure range of 0 -40 GPa. The calculated lattice parameters are well in agreement with expe...We employ density functional theory to study the mechanical, electronic and thermodynamic properties of the cubic NiTi in a prssure range of 0 -40 GPa. The calculated lattice parameters are well in agreement with experimental values and other calculated results, showing that the B2 NiTi is mechanically stable and no phase transformation occurs with pressure go-ing up to 40 GPa. The bulk modulus B, shear modulus G, Young＇s modulus E and B /G of B2 NiTi improve linearly with in-creasing pressure, implying that the volume change resistance, shear deformation resistance and elastic stiffness could also be strengthened by pressure. The pressure could also have an influence on the ductility of NiTi. The density of state （DOS） of Ni-Ti indicates that the bonding nature of B2 NiTi is metallic combining with covalent bonding, and pressure has no significant in-fluence on the electronic properties in a pressure range of 0 - 40 GPa. In addition, the dependences of temperature and pressure on Debye temperature ⊙D ,heat capacity Cv and Cp are further studied to figure out the thermodynamic properties of B2 NiTi.All above are especially useful to further study the properties of NiTi.展开更多
文摘Composites of NiTi2-TiB have been fabricated using spark plasma sintering and mechanical properties have been investigated. Dense specimens of monolithic NiTi2 have been obtained by the sintering at 950?C. By the x-ray diffraction measurements it has been shown that NiTi2 co-exists with TiB in equilibrium at 950?C. The bending strength of NiTi2-TiB composite increases with increasing the volume fraction of TiB2 up to 60 vol%. The maximum bending strength of 730 MPa has been obtained for NiTi2-60vol% TiB2. The Vickers hardness also increases with increasing the volume fraction of TiB up to 70% and the highest Vickers hardness of 1620 Hv has been obtained for NiTi2-70%TiB.
文摘Ti-Ni-Mo-Si composite coating was fabricated on mild steel by reactive braze coating process with Ti61. 9Ni24. 6Si4. 411409.1 （ wt. % ） powders as the raw materials. Microstr^cture of the coating was characterized by optical microscopy, scanning electron microscopy, X-ray diffraction and energy dispersive spectroscopy and micro-hardness tester. Results indicate that the Ti-Ni-Mo-Si composite coating is metallurgically bonded to the mild steel substrate and has high hardness. The microstructure of the coating consists of the reinforcement of Ti5 Si3 and Mo9 Ti4 particles and the matrix of eutectic NiTi2. Due to the poor wettability of NiTi2 liquid at low temperature, TisSi3 and Mo9 Ti4 do not uniformly distribute in the NiTi2 matrix.
基金National Natural Science Foundation of China(Nos.U1610123,51674226,51574207,51574206)International Cooperation Project of the Ministry of Science and Technology of China(No.2014DFA50320)+3 种基金Science and Technology Major Project of Shanxi Province(No.MC2016-06)International Science and Technology Cooperation Project of Shanxi Province(No.2015081041)Research Project Supported by Shanxi Scholarship Council of China(No.2016-Key 2)Transformation of Scientific and Technological Achievements Special Guide Project of Shanxi Province(No.201604D131029)
文摘We employ density functional theory to study the mechanical, electronic and thermodynamic properties of the cubic NiTi in a prssure range of 0 -40 GPa. The calculated lattice parameters are well in agreement with experimental values and other calculated results, showing that the B2 NiTi is mechanically stable and no phase transformation occurs with pressure go-ing up to 40 GPa. The bulk modulus B, shear modulus G, Young＇s modulus E and B /G of B2 NiTi improve linearly with in-creasing pressure, implying that the volume change resistance, shear deformation resistance and elastic stiffness could also be strengthened by pressure. The pressure could also have an influence on the ductility of NiTi. The density of state （DOS） of Ni-Ti indicates that the bonding nature of B2 NiTi is metallic combining with covalent bonding, and pressure has no significant in-fluence on the electronic properties in a pressure range of 0 - 40 GPa. In addition, the dependences of temperature and pressure on Debye temperature ⊙D ,heat capacity Cv and Cp are further studied to figure out the thermodynamic properties of B2 NiTi.All above are especially useful to further study the properties of NiTi.
