应力时效对2E12铝合金的力学性能和微观组织的影响

采用力学性能试验机、透射电子显微镜(TEM)、应力时效炉等手段研究时效拉应力对2E12铝合金的力学性能和微观组织的影响,并分析应力对2E12铝合金的作用机理.结果表明:外加应力能提高2E12铝合金的强度,增大合金各向异性的差异;外加应力能促进S相的析出,并产生明显的应力位向效应;应力时效能使2E12铝合金的无沉淀析出带变窄,阻止晶界沉淀相的连续析出;应力时效为控制高强铝合金的各向异性提供了一种新方法.     

时效处理对形变Cu-10Fe-3Ag原位复合材料组织及性能的影响

采用大气熔炼与形变原位复合的方法制备形变Cu-10Fe-3Ag原位复合材料。在不同温度时效6 h后,用SEM观察分析材料的显微组织;用XRD测定晶面间距的变化,分析合金元素Ag在时效过程中的行为规律和作用机制。结果表明:Ag能够促进γ-Fe在Cu基体中的时效析出,同时降低Fe纤维的热稳定性;随着时效温度的升高,形变Cu-10Fe-3Ag复合材料的硬度和导电率都是先增加后降低,在475℃时效6 h后,导电率达到58.4%IACS。合金的断口全是韧性断裂,随着时效温度的升高,韧窝变小。     

热暴露对航空用2E12铝合金组织演变及疲劳性能的影响

利用维氏硬度检测、疲劳性能测试、视差量热法(DSC)、透射电子显微分析(TEM)等手段,研究了航空用T3态2E12铝合金在150℃下分别暴露10 h,100 h,1000 h组织演变及疲劳寿命变化规律.结果表明:随热暴露时间的增加,合金硬度不断增大,疲劳寿命呈先增后降趋势;T3态及热暴露10 h合金中析出相由GPB区结构组成,热暴露10 h合金中GPB区发生长大,因而具有最长疲劳寿命;热暴露100 h至1000 h后,合金中析出相为S"相及S'相,析出相在晶界处析出,晶界附近形成无沉淀析出带(PFZ);由于S"相及S'相共格性较GPB区低,加之晶界处析出相易形成裂纹源,PFZ与基体协调性差等因素,热暴露100 h和1000 h后,合金疲劳寿命急剧下降.     

铌及铌合金高温抗氧化研究进展

铌及铌合金以其熔点高、耐腐蚀和良好的高温强度成为重要的高温结构材料。但高温抗氧化性能较差是制约其应用的关键问题。从铌的氧化机理、合金化抗氧化保护和表面涂层保护三方面，论述了铌及铌合金高温抗氧化的研究进展。分析了研究中面临的问题，并提出了解决途径。     

低钴WC-Co合金的真空烧结

一、引言自从本世纪60年代以来,国内外对WC-Co硬质合金的真空烧结技术进行了比较广泛构研究,其真空度多数在1～10Pa,最低在100Pa。     

化学镀铜及其应用

综述了化学镀铜技术及其发展趋势,对化学镀铜的原理、工艺、镀液组成等方面进行了全面的分析,最后对化学镀铜今后的研究方向提出了一些见解.     

高能球磨制备纳米掺La硬质合金粉末

用XRD、SEM和DTA等分析检测手段，研究了高能球磨过程中，掺La硬质合金粉末的结构、形貌和相的变化。结果表明：微量La的加入，有利于硬质合金粉末晶粒的细化；高能球磨10h，即可获得晶粒度为30nm的掺La硬质合金粉末；高能球磨20h,Co相的X－ray衍射峰消失，说明Co相已完全固溶或亚固溶于WC相中。高能球磨30h，可获得晶粒度约10nm的掺La硬质合金粉末。DTA分析表明，与高能球磨前的粉末相比，在300－600℃温度范围内加热时，高能球磨掺La硬质合金粉末出现了明显的结构弛豫，说明粉末晶粒内部产生了许多缺陷，如：内应力、位错、晶格畸变等。     

稀土复合氧化物陶瓷热导率理论及其热物性能

综述了稀土复合氧化物陶瓷热导率理论的发展情况和热物性能方面的研究现状,介绍了材料热导率的影响因素,分析了材料微结构对热导率的影响,总结了具有A2B2O7通式的烧绿石型和萤石型稀土复合氧化物的热物性能,以及掺杂对其热导率和热膨胀系数的影响.     

Effect of rare earth doping on thermo-physical properties of lanthanum zirconate ceramic for thermal barrier coatings

The effect of rare earth doping on thermo-physical properties of lanthanum zirconate was investigated. Oxide powders of various compositions La2Zr2O7 were synthesized by coprecipitation-calcination method. High-temperature dilatometer, DSC, and laser thermal diffusivity methods were used to analyze thermal expansion coefficient （TEC）, specific heat, and thermal diffusivity. The results showed that CeO2 doped pyrochlores La2（Zr1.8Ce0.2）2O7 and La1.7（DyNd）0.15（Zr0.8Ce0.2）2O7 had higher TEC than La2Zr2O7 and La1.7Dy0.3Zr2O7. La2（Zr1.8Ce0.2）2O7, La1.7Dy0.3Zr2O7, and La1.7（DyNd）0.15（Zr0.8Ce0.2）2O7 had lower thermal conductivity than undoped La2Zr2O7. The Dy2O3, Nd2O3, and CeO2 codoped composition showed the lowest thermal conductivity and the highest TEC. Thermo-physical results also indicated that TEC of rare earth oxide doped La2Zr2O7 ceramic was slightly higher than that of conventional ZrO2-8Wt.% Y2O3 （8YSZ）, and its thermal conductivity was lower than that of 8YSZ.     

Effects of yttrium on recrystallization and grain growth of Mg-4.9Zn-0.7Zr alloy

Recrystallization and grain growth in Mg-4.9Zn-0.7Zr and Mg-4.9Zn-0.9Y-0.7Zr alloys as a function of temperature on deformation were investigated with regards to hot rolling and annealing. The influence of yttrium addition on the microstructure was examined by X-ray diffraction （XRD）, optical microscopy （OM）, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM）. The results indicated that yttrium addition promoted nucleation of recrystallization during hot rolling process. The grain size of Mg-4.9Zn-0.7Zr alloy samples grew significantly with annealing temperature （300-400 ℃） and holding time （0-120 min）, while the microstructure of the alloy with yttrium addition remained unchanged and fine. The activation energy of grain boundary migration for Mg-4.9Zn-0.9Y-0.7Zr alloy samples （56.34 kJ/mol） was higher than that for Mg-4.9Zn-0.7Zr （42.66 kJ/mol） owing to the pinning effect of Y-containing particles. The proposed growth models of recrysta/lized grains for the two studied alloys conformed well to E. Robert＇s grain-growth equation. Besides, the ultimate strength and yield strength of the alloys with yttrium addition were improved with good plasticity.