Effects of can parameters on canned—forging process of TiAl base alloy（Ⅱ）——Mechanical behavior

1　ＩＮＴＲＯＤＵＣＴＩＯＮＴｉＡｌａｌｌｏｙｈａｓｌｏｎｇｂｅｅｎｃｏｎｓｉｄｅｒｅｄａｓａｐｒｏｍｉｓ ｉｎｇｍａｔｅｒｉａｌｆｏｒｈｉｇｈｔｅｍｐｅｒａｔｕｒｅａｐｐｌｉｃａｔｉｏｎ ,ｄｕｅｔｏｉｔｓｅｘｃｅｌｌｅｎｔｈｉｇｈｔｅｍｐｅｒａｔｕｒｅ ｐ     

Friction and wear properties of pitch／resin densified carbon—carbon composites used for airbrakes

By use of X-ray diffractometry and scanning electron microscope(SEM),the friction and wear results obtained from MM-1000 dynamometer tests of CVI pitch/resin C/C composites were analyzed.By investigating the factors that affected the friction and wear properties,such as matrix carbon,applcation environment,graphitization degree and brake pressure,etc,friction and wear mechanism of carbon materials were probed.The results indicate that pitch densified CVI initially treated composite is more graphitizable with its graphitization degree up 59 62%,and which results in uniform small debris easier to generate,more smooth friction curves with the coefficient of 0.3-0.4 and relatively higher wear and mass loss,compared with CVI/resin C/C composites.It was further proved by SEM observation that tribological behavior of C/C composite was system dependent.Factors determining the friction and wear properties such as the size of debris and its influence on friction and wear,brake pressure,graphization degree and debris bilm formation interacted and affected each other.The friction and wear mechanism of C/C composites under different high temperature treatments needs further research.     

金属注射成形技术进展

分析了影响金属注射成形（ＭＩＭ）产业化进程的两个主要技术因素，即适合ＭＩＭ要求的原料粉末的生产方法和ＭＩＭ生产工艺，并概述了目前ＭＩＭ技术的发展状况。     

Microstructure and hardness of binary Cr-Ta alloys

The dependances of the microstructure and hardness of the binary Cr-Ta alloys [ Cr-9.0, -9.2, -9.4, -9.6,-9.8, and -13.0 Ta] (mole fraction, %) were investigated. When Ta content of the alloy is less than 9.4%, there are primary dandrite grains of a Cr solid-solution phase existing in the matrix of Cr-Cr2Ta eutectic colonies in the alloy. Moreover, the regular polygon grains of the primary Cr2Ta Laves-phase are surrounded by the Cr-Cr2Ta eutectic colony in the hyper-euteetic Cr-9.4 96 Ta alloys. The scanning electron microphotograph shows that one of the Cr2Ta phase plates of an eutectic colony always connects with the primary Cr2Ta Laves-phase grain in a hyper-eutectic alloy. The eutectic colony size of Cr-Ta alloys decreases with increasing Ta. In addition, the macrohardness of Cr-Ta alloys is influanced by the chemical composition at room temperature. The binary eutectic Cr-Ta alloy presents the lowest hardness on a macrohardness scale.     

Mo对P／M Ti-Mo合金烧结致密化和力学性能的影响

研究了P／M Ti-Mo合金中Mo对烧结致密化及力学性能的影响。用热膨胀仪分析了其收缩／膨胀特性，用扫描电镜及力学性能检测等分析手段研究了显微组织和力学性能。结果表明，Mo的添加不利于P／M Ti-Mo合金的烧结致密化，但有利于Ti-Mo合金的显微组织细化。随着Mo含量的增加，组织细化作用更加明显。该晶粒细化作用大大改善了合金的室温塑性，使烧结态Ti-Mo合金的延伸率达到23％。     

Ti—33Al—3Cr—0.5Mo合金全层片组织晶粒尺寸对其高温抗氧化…

对全层片组织３种尺寸的试样进行了９００℃，７２ｈ的高温循环氧化增重试验，研究了晶粒尺寸对Ｔｉ－３３Ａｌ－３Ｃｒ－０．５Ｍｏ合金高温抗氧化性能的影响。结果表明：晶粒尺寸居中的试样具有良好的高温抗氧化性能，另外，用ＳＥＭ和ＥＤＡＸ分析了氧化层结构并探讨了氧化机理。     

Anti-oxidation mechanism of SiC-B4C-C composites

Mixture of green petroleum coke, B4 C and SiC together with short carbon fiber were employed as starting materials, the mixture was press formed without any binder after grinding, dense and homogeneous binderless SiC-B4 C-C（carbon/ceramic） composites were then obtained after sintering. Composites thus prepared possess excellent anti-oxidation property, that is, mass loss less than IG within the temperature range from 900 to 1 100 ℃ for 10 h. Anti-oxidation mechanism was also discussed from the viewpoint of thermodynamics, excellent anti-oxidation property of materials thus prepared can be discribed to 1） solid SiO2 formed from SiC, which restrains the filtering of oxygen and simultaneously, its volume expansion brought about by the reaction takes roles both walling up the original pores and making the material more compact; 2） liquid B2O3 from the reaction of B4C not only makes the combination with C, B4 C and SiC tighter through forming solid solution, but also effect of reaction SiC（s）＋2CO（g） =SiO2 （s）＋3C（s） is an expansive process, which improves the microstructure of the material.     

TaC涂层的氧化特征与氧化机制

用在空气中氧化、氧炔焰超高温烧蚀等方法对TaC涂层在不同温度的氧化特征与氧化机制进行研究。研究结果表明：TaC在508℃以上开始氧化,在508～690℃时氧化产物为六角Ta2O3固溶体,690～900℃时氧化产物转化为斜方Ta2O5晶体,900～1500℃时氧化产物为斜方Ta2O5,其形态为龟裂或多孔烧结态,未能形成对TaC的隔离保护膜;1500℃氧化时出现部分Ta2O5液相与Ta2O5斜方相共存的现象;在氧炔焰超高温2300℃烧蚀时形成大量的Ta2O5熔体液膜,熔体与TaC的润湿性很好。TaC涂层由低温无熔体情况下界面反应控制机制变为氧通过熔体溶解与扩散的控制机制。     

SiCp/AlCuMgAgCe复合材料的显微组织与力学性能

采用压铸浸渗法制备了53%SiCp增强的AlCuMgAgCe基复合材料。通过X射线衍射、金相观察、扫描电镜与透射电镜分析以及力学性能测试,研究了SiCp/AlCuMgAgCe复合材料的显微组织与力学性能。结果显示,在AlCuMgAgCe合金中加入53%体积分数的SiC颗粒后,复合材料的组织致密,分布均匀,其断裂方式包括界面脱开、基体韧断和增强体开裂,SiC颗粒与基体之间并没有发生明显的界面反应。在185℃的等温时效析出过程中,复合材料的析出相主要由Ω相和少量θ′相组成。     

Ni对C－B_4C－SiC复合材料显微结构与性能的影响

本文研究了烧结助剂Ｎｉ对Ｃ－Ｂ_４Ｃ－ＳｉＣ复合材料显微结构与性能的影响．Ｘ射线衍射表明Ｎｉ在烧结温度下与ＳｉＣ，Ｂ_４Ｃ人发生反应在晶界生成Ｎｉ_（４．６）Ｓｉ_２Ｂ，并产生液相，有效地促进了Ｃ－Ｂ_４Ｃ－ＳｉＣ复合材料的烧结，抑制了晶粒的长大，使复合材料密度与强度大幅度地增加，电阻率下降；同时Ｎｉ_（４．６）Ｓｉ_２Ｂ在氧化时生成致密的２ＮｉＯ·Ｂ_２Ｏ_３，包裹了易氧化的Ｂ_４Ｃ和Ｃ，有效地防止了复合材料的氧化，从而大大提高了制品的抗氧化性能．