In situ evaluation of the transformation behaviour of NiTi-based high temperature shape memory alloys

Fine grained polycrystalline NiTi shape memory alloys containing 15 at.% Hf and Zr and zero or 3 at.% Cu fabricated by ingot metallurgy were investigated using in situ synchrotron X-ray diffraction in order to examine the viability of producing stable and affordable high temperature shape memory alloys. The alloys produced had a high thermal hysteresis, in excess of 70 °C but A_f temperatures of over 250 °C were obtained for Ni₅₀Ti₃₅Hf₁₅. 3 at.% Cu additions did not significantly reduce the per-cycle degradation of transformation temperatures but did reduce the transformation temperatures. The evolution of the lattice parameters during the first five thermal cycles was observed. Negative thermal expansion was found in the b_B19′ cell direction in all the alloys examined and significant deviations in the lattice parameters in the region of transformation were found. A per-cycle evolution in the end-point B19′ lattice parameters was observed, but no such evolution was found for the B2 phase, which is rationalised by appealing to the increase in population of interface dislocations.     

《工程材料学》CAI网络教学平台的开发

介绍了计算机在《工程材料学》课程教学中的应用,阐述了网络教学平台的理论基础、设计原则和基本特点。并运用多媒体技术和网页制作软件,建立了《工程材料学》课程网络教学网站,探索了网络教学对教学模式的变革和创新。     

稻壳灰制备掺杂TiO2硅气凝胶研究

以稻壳为硅源制备SiO2气凝胶，在溶胶凝胶过程中加入TiO2纳米粉末，可制得掺杂TiO2硅气凝胶。通过SEM、BET吸附．脱附测试等手段，与同种方法制得的纯SiO2气凝胶在结构和物性特征方面等进行了比较。结果显示，掺杂TiO2气凝胶的平均颗粒直径为50nm左右，而纯SiO2气凝胶的粒径约为20nm，且孔洞直径明显减小、孔径分布更为均匀；此外，TiO2纳米粉末的加入可以使气凝胶的弹性模量提高约23％，并且通过TiO2对气凝胶溶胶-凝胶过程的影响研究了其影响机理。     

Effect of Y203 on microstructure and oxidation of γ-Ni＋γ′-Ni3Al coatings transformed from electrodeposited Ni-Al films at 1 000℃

The electrodeposited Y2O3-dispersed γ-Ni＋γ-Ni3Al coatings on Ni substrates were developed by the conversion of electrodeposited Ni-Al-Y2O3 films with dispersed AI microparticles in Ni matrix into Ni3Al by vacuum annealing at 800 ℃ for 3 h. For comparison, Y2O3-free γ-Ni＋γ＇-Ni3Al coatings with a similar AI content were also prepared by vacuum annealing the electrodeposited microparticle-dispersed composite coatings of Ni-AI under the same condition. SEM and TEM characterizations show that the electrodeposited Y2O3-dispersed γ＋γ＇ coatings exhibit finer grains, a more homogeneous distribution of γ＇, and a narrowed γ＇ phase spacing compared with the electrodeposited Y2O3-free γ-γ＇ coatings. The oxidation at 1 000 ~C shows that the addition of Y2O3 significantly improves the oxidation resistance of the electrodeposited γ＋γ＇coatings. The effect of Y2O3 particles on the microstructure and oxidation behavior of the electrodeposited γ＋y＇ coatings was discussed in detail.     

钛合金表面氩弧熔覆原位合成TiB2-TiN涂层组织及耐磨性能

以BN和Ni60A合金粉末为熔覆材料,采用氩弧熔覆技术在TCA合金表面原位合成TiB2-TiN增强颗粒耐磨涂层．利用x射线衍射仪、扫描电子显微镜和摩擦磨损试验机对熔覆层的组织和性能进行分析测试．结果表明,复合涂层的显微组织沿层深方向分为熔覆区、结合区和热影响区;熔覆层与基体呈良好冶金结合,TiB2-TiN颗粒弥散分布,...     

余热法制备高性能钢铁复合发黑膜的研究

为了增加钢铁余热发黑保护膜的厚度,提高保护膜的耐腐蚀性能,采用热分析技术,测定了保护膜的耐热温度,通过二次成膜,制备出了厚而致密的有机复合保护膜.研究、分析了有机膨润土对钢铁余热发黑有机复合保护膜耐热性、耐腐蚀性的影响.结果表明:有机膨润土可提高、改善保护膜的耐热性,利于再次加热二次成膜.二次成膜厚度为18μm时,用5...     

材料类专业《物理化学》课程教学方法改革探索

物理化学是材料科学与工程类专业必修的一门专业基础课,该课程公式多,学习难度大。本文结合材料专业的特点,阐述了物理化学课程教师应将板书与多媒体课件有机结合起来,充分调动学生的积极性和主动性,并利用CAI网络教学辅助课堂教学,培养学生的学习兴趣,改善教学效果,促进应用型人才的培养。     

提高材料物理化学本科教学效果的探索

材料类专业的物理化学课程教学与化学类等专业有明显的区别,针对其具体的特点,从教材选择、课堂讲授、实验教学等方面探讨了提高教学效果的方法,并在实践中收到了良好的效果。     

Al_2O_3和Y_2O_3改性的低温渗铬涂层的循环氧化和热腐蚀性能

采用在Ni基上复合电镀Ni—Al_2_O3和Ni-Y_2_O3复合涂层后在800℃下扩散渗铬的方法,分别制备了Al_2O_3和Y_2_03改性渗铬涂层。采用相同的工艺在单Ni镀层上直接渗铬,获得一种不含氧化物粒子的渗铬涂层。分析了Al_2O_3和Y_2O_3影响渗铬涂层的氧化和腐蚀性能的机理。组织结构分析表明,Al_2O_3和Y_2O_3能明显抑制在渗铬过程中涂层品粒的长大。800℃循环和75％Na2SO4＋25％NaCl混合盐腐蚀试验结果表明：与在单Ni镀层上直接渗铬相比,A1203和Y_20_3改性的渗铬涂层所具有的细晶结构促进了保护性氧化物形成元素Cr沿晶界向氧化前沿的快速扩散,从而有利于致密保护性Cr_2O_3氧化膜的快速形成,使得改性的渗铬涂层表现出更优异的抗循环氧化和混合盐热腐蚀性能。     

Preparation and oxidation behaviour of electrodeposited Ni–CeO2 nanocomposite coatings

Ni–CeO₂ nanocomposite coatings with different CeO₂ contents were prepared by codeposition of Ni and CeO₂ nanoparticles with an average particle size of 7 nm onto pure Ni surfaces from a nickel sulfate. The CeO₂ nanoparticles were dispersed in the electrodeposited nanocrystalline Ni grains (with a size range of 10–30 nm). The isothermal oxidation behaviours of Ni–CeO₂ nanocomposite coatings with two different CeO₂ particles contents and the electrodeposited pure Ni coating were comparatively investigated in order to elucidate the effect of CeO₂ at different temperatures and also CeO₂ contents on the oxidation behaviour of Ni–CeO₂ nanocomposite coatings. The results show that the as-codeposited Ni–CeO₂ nanocomposite coatings have a superior oxidation resistance compared with the electrodeposited pure Ni coating at 800 °C due to the codeposited CeO₂ nanoparticles blocking the outward diffusion of nickel along the grain boundaries. However, the effects of CeO₂ particles on the oxidation resistance significantly decrease at 1050 °C and 1150 °C due to the outward-volume diffusion of nickel controlling the oxidation growth mechanism, and the content of CeO₂ has little influence on the oxidation.