Thermoelectric properties of mechanically alloyed iron disilicides consolidated by various processes

Mn doped p-type iron disilicide powders have been produced by a mechanical alloying process. As-milled powders were of metastable state and mostly transformed to β-FeSi₂ phase by subsequent isothermal annealing. As-milled powders were consolidated by various processes such as sintering of the cold compact in vacuum, vacuum hot pressing (VHP), and spray drying/atmospheric plasma thermal spraying. Phase transitions during the processes were investigated using XRD, EDS, and SEM. As-consolidated specimens consisted of a mixture of α-Fe₂Si₅ and ε-FeSi phases, which were gradually transformed into a thermoelectric semiconducting α-FeSi₂ phase by subsequent isothermal annealing in the vicinity of 845°C in vacuum. However, some residual α and ε phases remained even after prolonged annealing. Thermoelectric properties were measured as a function of temperature and correlated with phase transformation. They showed optimum values in the vacuum hot pressed specimen due to a higher fraction of β phase and/or higher density.     

气相缓蚀剂的研究现状与展望

从缓蚀剂的缓蚀基团和分子结构方面概述了气相缓蚀剂的研究现状，阐述了气相缓蚀剂的有关缓蚀机理。分析了缓蚀效果的影响因素．讨论了气相缓蚀剂的发展方向．     

精密逆变电阻点焊的应用

首先介绍了精密逆变电阻点焊机系统，包括系统的组成，特点，然后介绍几种典型工件的焊接工艺，结果表明，这种焊机在精密零件 的电阻点焊中有其独持的工艺优势，有很好的推广应用价值。     

晶体取向和载荷模式对Ni3Al合金单晶体疲劳行为的影响

在名义Ⅰ型和Ⅰ／Ⅱ复合型载荷下研究了晶体取向和加载模式对Ｎｉ３Ａｌ合金单体疲劳开裂行为的影响。结果表明：疲劳开裂行为强烈地依赖于晶体取向和加载模式。在单晶体中，站劳裂纹总是沿着具有最大切应力的滑移须开裂。根据单晶体的实验结果，解释了用三种主要的复合型断裂准则所预测的多晶体在复合型加载下的疲劳开裂行为。     

用偏钛酸作原料制备纳米TiO2粉末以及颗粒相结构与光催化性能关系的研究

米用常温氨水水解TiOSO4过程中加入自制的表面活性剂制备了超细纳米TiO2粉末,用XRD,TEM和比表面仪对不同煅烧温度下的纳米TiO2粉末结构、粒径大小和比表面等进行了表征,研究了纳米TiO2粉末对甲基橙的光催化降解能力。研究表明煅烧温度在400℃～800℃时得到的纳米TiO2粉末呈锐钛矿结构,粒径约为5．5nm～9．6nm,比表面积高达189．45m^2/g;在850℃煅烧后所得的纳米TiO2粉末为锐钛矿与金红石型混晶结构;在l100℃时得到的纳米TiO2粉末为金红石型纳米TiO2粉末,同时微粒出现团聚且粒径变大。光催化实验表明：纳米TiO2粉末的光催化活性与煅烧温度密切相关,850℃煅烧1．5h所制得的混晶结构纳米TiO2粉末表现出较高的光催化活性。与国产商品纳米锐钛矿型TiO2相比,其降解甲基橙的速率约为国产商品纳米TiO2的1倍。     

Ni含量对TiNi形状记忆合金相变行为的影响

用示差扫描热分析仪和光学显微镜系统研究了Ｎｉ含量对ＴｉＮｉ形状记忆合金Ｒ相和Ｍ相相变温度，相变热，热滞的影响。结果表明：在加热和冷却过程中，Ｔｉ－３３．３％Ｎｉ和Ｔｉ－７５．０％Ｎｉ不发生相变；ＴＭ，ΔＭ，ΔＨＭ和ΔＨＲ是Ｎｉ是含量的函数，ＴＲ和ΔＲ基本为一定值，与Ｎｉ含量有关。     

The influence of chromium on mechanical properties of austempered ductile cast iron

An investigation was carried out to examine the influence of microstructure and chromium on the tensile properties and plane strain fracture toughness of austempered ductile cast iron (ADI). The investigation also examined the growth kinetics of ferrite in these alloys. Compact tension and round cylindrical tensile specimens were prepared from ductile cast iron with Cr as well as without Cr. These specimens were then given four different heat treatments to produce four different microstructures. Tensile tests and fracture toughness tests were carried out as per ASTM standards E-8 and E-399. The crack growth mechanism during fracture toughness tests was also determined. The test results indicate that yield strength, tensile strength, and fracture toughness of ADI increases with an increase in the volume fractions of ferrite, and the fracture toughness reaches a peak when the volume fractions of the ferrite are approximately 60% in these alloys. The Cr addition was found to reduce the fracture toughness of ADI at lower hardness levels (<40 HRC); at higher hardness levels (≥40 HRC), the effect of chromium on the fracture toughness was negligible. The crack growth mechanism was found to be a combination of quasi-cleavage and microvoid coalescences, and the crack trajectories connect the graphite nodules along the way.     

PMN-PNN-PT单晶的固相法生长研究

采用两步法和埋入PMN-PT单晶为模板的等离子放电烧结（SPS）技术制备出了致密的单一钙钛矿相的PMN-PNN-PT陶瓷，随后在1200℃下退火100h来诱导晶体的生长。实验结果表明，PMN-PNN-PT单晶〈111〉方向的生长速度明显快于〈001〉方向，而〈111〉方向生长的晶体形状为V字形，这是由钙钛矿结构的生长机理决定的，钙钛矿结构晶体的生长是通过〈001〉方向的层状生长来实现的。     

镍基单晶合金枝晶典型区域相成分最优化测算法

建立了用于测算镍基单晶高温合金枝晶典型区域相成分的最优化数学模型.根据电子探针对枝晶典型区域成分的测定结果,运用BFGS拟Newton法及CONSTR约束优化算法,可以计算枝晶各典型区域中γ和γ＇相成分.以镍基单晶合金CMSX-2和CMSX-4为对象,对优化测算结果进行了分析,证实了该方法的可行性.     

热处理对铁铝涂层相组成及滑动磨损性能的影响

采用粉芯丝材和高速电弧喷涂技术得到的铁铝金属间化合物涂层 ,研究了 5 5 0℃和 80 0℃热处理对涂层相组成及滑动磨损性能的影响。结果表明 ,涂层的主要组成相是铁铝金属间化合物 (FeAl和Fe3 Al)和α Fe ,另有少量的Al2 O3 和Al。热处理后 ,一部分Fe3 Al将转变成FeAl,对涂层的显微硬度有明显的影响。剥层磨损是铁铝涂层的主要磨损机理。通过热处理提高涂层的显微硬度 ,将有利于提高涂层的耐磨性