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Tang G.,Xian Jiaotong University | Zhang J.,China Shipbuilding Industry Corporation | Jiao Y.,Xian Jiaotong University | Dong G.,Xian Jiaotong University | Yang H.,Xian Saite Metal Materials Development Co.
Zhenkong Kexue yu Jishu Xuebao/Journal of Vacuum Science and Technology

The tribological property of the TiNi coatings, synthesized by magnetron sputtering on the surfaces of machines ' linear rolling guide, was improved by oxidation. The impact of the oxidation techniques: in-situ vacuum oxidation at 550℃ and ex-situ anodized oxidation, on the tribological property of TiNi coatings was investigated. The mi-crostructures and mechanical properties of the TiNi coatings, before and after oxidation, were characterized with X-ray diffraction, scanning electron microscopy, and conventional mechanical probes. The preliminary results show that both oxidation techniques significantly reduce the friction coefficient of the TiNi coatings. For instance, under dry friction condition, the friction coefficient of the TiNi coating was reduced to 0.17~0.19, 60% lower than that of the control sample (0.4~0.6). Moreover, when it comes to wear-resistance and friction damages, in-situ thermal oxidation outperforms ex-situ anodized oxidation. ©, 2014, Science Press. All right reserved. Source

Wang J.G.,Xian Saite Metal Materials Development Co. | Wang J.G.,Beihang University | Liu F.S.,Beihang University | Cao J.M.,Xian Saite Metal Materials Development Co.
Materials Science and Engineering A

This work presents a study of a novel Ti50Ni47Fe2.5Nd0.5 shape memory alloy by EPMA, E-R analysis and tensile tests. Structural characterization shows the alloy consists of TiNiFe matrix, Nd3Ni and Ti2Ni intermetallic compounds with Fe solute. The latter two phases are well distributed in the matrix. Compared with Ti50Ni47.5Fe2.5 alloys without rare earth Nd, the novel alloy does not change the two-stage martensitic transformation behavior, however, characteristic temperatures increase rapidly. The critical stress needed for inducing martensitic transformation is near linear relationship with the increasing of the testing temperature above Ms, which is in good agreement with Clausius-Clapeyron equation. The novel alloy exhibits an improved shape memory effect as a consequence of precipitation strengthening and the maximum recoverable strain attains to 7.8%. © 2010 Elsevier B.V. Source

Dong G.,Xian Jiaotong University | Dong G.,CAS Lanzhou Institute of Chemical Physics | Zhang J.,The 704th Institute of Shanghai | Zhang D.,Xian Jiaotong University | And 3 more authors.
Xiyou Jinshu Cailiao Yu Gongcheng/Rare Metal Materials and Engineering

The micro-crater texture of TiNi alloy was voluminously indented by a mold. Results show that the geometrical parameters of the texture will modify the tribological properties. With increasing of the circumferential pitch and the radial spacing of texture, the friction coefficient and wear rate of TiNi alloy present a decrease at the start, and then an increase after a minimum point. With gradual increasing of the ratio of depth to diameter, the friction coefficient and wear rate of TiNi alloy increase initially and then tend to decrease. When the sliding speed increases, the friction coefficient of TiNi alloy decreases firstly and then increases, following Stribeck curve. With the selected texture parameters such as micro-crater ratio of depth to diameter of 0.06, the radial distance of 1.5 mm, circumferential pitch of 15°, the surface show the best tribological properties of the friction coefficient of 0.098 and wear rate of 0.87 × 10-5mm3/N · m. It is concluded that the texture with appropriate parameters and shapes can reduce the friction coefficient and wear because of micro-hydrodynamic lubrication and the capture of wear debris from micro-crater texture. © 2011, Northwest Institute for Nonferrous Metal Research. Published by Elsevier BV. All rights reserved. Source

Fan Y.,Xian Saite Metal Materials Development Co. | Cao J.,Xian Saite Metal Materials Development Co. | Wang W.,Xian Saite Metal Materials Development Co. | Liu Y.,Xian Jiaotong University
Materials Science Forum

With massive trials, spheroidized by austeniting at 810°C and cooling by 1°C/min, a 1.6C (pct) Ultra-high Carbon Steel shows a microstructure of uniformly distributed fine carbides in the ultra-fine ferrite matrix. The grain size of ferrite matrix and spheroidized carbides are about 5um and 0.1∼2um, respectively. Further investigation by TEM shows that much dislocation together with twins is obtained for the UHCS, and generally finer grains have higher dislocation density. The spheroidized steel exhibits high tensile strength of 910 MPa and high yielding strength of 653 MPa at room temperature, together with excellent elongation of 18.3%, which shows the UHCS can entirely satisfy certain grades of engineering materials and means the steel may substitute present engineering steel considering lower cost. Furthermore, the steel owns good high-temperature superplasticity, the elongation of 216% obtained at 800°C under a strain rate of 2.5×10-4. Initial analysis suggests that the superplastic deformation mechanics of the steel is grain boundary sliding and grain rotating (GBSR), coordinated by migration of dislocation. Source

Li L.,Xian Saite Metal Materials Development Co. | Cao J.,Xian Saite Metal Materials Development Co. | Xiao S.,Xian Saite Metal Materials Development Co. | Cao R.,Lanzhou University of Technology | And 2 more authors.
Xiyou Jinshu/Chinese Journal of Rare Metals

The compression deformation and damage behavior of TiAl based alloys were studied by measurement of mechanical properties, SEM observations and FEM calculation. The results showed that: No appreciable effects of the preloading-unloading-reloading processes on global compression deformation behavior were produced, until compression preloading stress surpassed the maximum compression stress. Because of the accumulation of damage effects, the big main crack was formed, and then the true loading cross-section was descended, so the fracture stress was reduced when the specimen was reloaded again. Under the compression condition: firstly, surface microcracks paralleled to compression axis, which around the slip line and extrusion ridge, were produced and expanded rapidly. The surface microcracks density increased significantly. Compared with the microcracks paralleled to compression axis, the microcracks on the direction of 45 ° were propagated along the layer, but there was no exactly equivalent the microcracks to the grain in size (100~300 μm). Secondly, four types of microcracks were initiated and propagated on the surface of the specimens with smaller normal stress in the compression process: longitudinal interlamellar cracks paralleled to the compression axis; interlamellar cracks inclined to the compression axis with a small angle; longitudinal translamellar cracks inclined to the compression axis with a small angle; longitudinal trans-granular crack. Source

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