Coating of TiB2 dispersed Ti50Ni50 superelastic alloy layer onto Ti-6Al-4V alloy by spark and resistance sintering

The spark and resistance sintering (SRS) of a mixture of Ti, Ni, and TiB₂ powders was carried out to form a TiB₂ dispersed TiNi alloy layer onto a Ti-6Al-4V alloy substrate. The strength and delamination resistance of the surface layer were evaluated by three-point bending tests. The results showed that the bending strength of the specimen with the TiNi alloy surface layer without TiB₂ particles sintered at 1273 K was low because the crack initiation occurred at an early stage of loading in a thick interface layer containing brittle Ti-Ti₂Ni eutectic. By decreasing the sintering temperature to 1200 K, the bending strength increased and the crack initiation occurred from the surface because the interface layer was thin and did not contain the brittle Ti-Ti₂Ni eutectic. For the specimens with TiB₂ dispersed TiNi surface layer that was sintered at 1273 K, the bending strength was larger than that of the specimens with TiNi surface layer because the interface layer does not contain the Ti-Ti₂Ni eutectic and compressive residual stress generated in the surface layer during cooling process after SRS suppresses the crack initiation on the surface. The coating of TiB₂ dispersed TiNi alloy onto titanium alloys by SRS provides strong interface to prevent delamination of the surface layer, strong surface due to residual compressive stress, and wear-resistant surface due to the existence of hard TiB₂ particles and superelastic deformation of TiNi matrix.     

Influence of sintering temperature on the shrinkage and geometrical characteristics of steel parts produced by powder metallurgy

The dimensional and geometrical characteristics of Charpy bars produced with two different steels were investigated to evaluate the effect of increasing the sintering temperature from 1120 °C (conventional sintering temperature) up to 1350 °C. The problem was approached from the Geometric Dimensioning and Tolerancing (GD&T) point of view, referring to the standard ASME Y14.5 (2009). The dimensional and geometrical characteristics were evaluated using a Coordinate Measuring Machine (CMM), measuring the surfaces by scanning mode. The work highlights that the increase in the sintering temperature, aimed at improving the mechanical properties, does not prevent the main benefit of this technology, i.e., the possibility of producing parts with good dimensional and geometrical precision. Moreover, a methodology establishing the measurement procedures and data processing, to be used in future work for the characterisation of more complex shapes, was defined.     

On the strength of polycrystalline tungsten monocarbide

The paper consists of analytical and applied parts. The mathematical means of mechanics of hexagonal polycrystals are used in the former. Here the correspondence of the published data on single crystal elastic constants of tungsten monocarbide to elasticity moduli of polycrystalline WC has been analyzed. The relationship between ultimate tensile stress and ultimate compressive stress of polycrystalline tungsten monocarbide has been established too. The dependence of ultimate tensile stress and ultimate compressive stress of polycrystalline tungsten monocarbide on mean grain diameter is considered in the applied part. Here the available experimental data are used.     

实现我国承诺的2020年减排指标的设想

介绍气候变化的危害原因和我国能源利用效率与发达国家的差距,提出推进碳减排工作及发展低碳经济,以实现我国承诺的2020年减排指标的设想。     

高校中水系统研究与规划

针对国内高校用水现状,研究了高校中水系统的水源选用、处理工艺、管路设置及系统方案比较等技术原则,为高校中水系统的优化设计、合理设置和科学规划提供参考。     

质量高于利润服务高于利润——浅谈白蚁防治行业的企业道德文化

文章从树立正确的道德规范、建立良好的行业信誉、树立客户至上的观念、创造公平有序的竞争环境等四个方面提出了培育白蚁防治行业道德文化的对策。     

防控甲流期间做好团学活动的思考

本文在分析了防控甲流工作的重要性以及团学活动的重要意义的前提下,初步探讨了在防控甲流期间做好团学活动的具体措施。     

钢筋混凝土框架结构施工技术

对多层框架结构施工过程中遇到的技术问题及解决方案进行论述,对做好类似工程的施工技术工作具有借鉴意义。     

一种释放负离子面膜的研制

论述了一种负离子面膜的研制过程。在面膜的制作过程中通过适当的途径加进负离子添加剂,从而使负离子在皮肤表面发挥还原性作用,使已经氧化的皮肤还原,恢复健康状态。通过多次实验,所得产品负离子释放量超过了700个/cm3,具有释放负离子稳定持久、发射远红外线、杀菌、消毒、保健等功效,达到了健康要求。     

高等学校文科数学教学改革与实践

本文结合南京工业大学十多年来文科数学课程的教学实践,围绕大学文科专业开设数学课程的必要性和重要性以及文科数学的课程体系、教学内容、教学方法、教学手段等方面,作了初步的探讨和研究。