喷射成形与铸造7A60合金的微观组织对比研究

利用喷射成形技术制备了7A60合金。借助扫描电镜（SEM），透射电镜（TEM），X射线衍射（XRD）等手段研究了喷射成形与铸造7A60合金微观组织的特点。结果表明，铸造7A60合金的组织粗大，偏析严重。喷射成形7A60合金主要由细化的等轴晶组成，无明显偏析。与传统铸锭冶金工艺相比，喷射成形工艺大大提高了冷却速率，显著细化了7A60合金的微观组织。     

热处理工艺对高钒高速钢组织与滚动磨损性能的影响

研究了20种热处理工艺对高钒高速钢的硬度、冲击韧性、残余奥氏体量与滚动磨损性能的影响,并利用SEM对其显微组织进行了分析,筛选出了适合滚动磨损的热处理工艺。研究结果表明:淬火温度升高,其残余奥氏体量升高;回火温度升高,其残余奥氏体量减少。淬火温度为900～1 000℃时,回火温度对耐磨性的影响不大;1 050～1 100℃淬火,450～550℃回火时,滚动磨损性能大幅度提高。以滚动耐磨性为评价指标,综合考虑热处理工艺对力学性能、滚动耐磨性、设备损耗及生产成本的影响,最适宜的热处理工艺为:淬火加热温度1 050℃,回火温度450～550℃。     

近2年我国锆铪及锆化学制品雕生产、贸易及研发概况

介绍了我国近2年来海绵锆、锆铪制品和锆化学品的生产、进出口概况,以及重要研发进展。我国工业级海绵锆产量从2003年的100t增加到2005年的174t,2005年的销售量达到150t;锆粉与锆-铝消气剂等年产量在10t左右;锆材和锆设备年产量在100t以上;锆化学制品品种有10余种,年产量已达到20×104t。锆砂的沸腾氯化工艺、锆铪的MIBK法分离工艺、以电熔ZrO2为原料制取粗ZrCl2工艺和Al-Y复合ZrO2粉的生产工艺等的研发工作,都取得了突破性进展。     

Direct laser fabrication of thin-walled metal parts under open-loop control

Direct laser fabrication (DLF) is an advanced manufacturing technology, which can build full density metal parts directly from CAD files without using any modules or tools. The investigation on the fabrication of thin-walled parts of nickel alloy using open-loop DLF process is introduced in this paper. The experimental setup consisted of a CO₂ laser, a 3-axis CNC table, a coaxial powder nozzle and a powder recycler. The 3D-CAD file of a thin-walled metal part was converted into the STL file format and imported into software HUST-RP to generate ‘pseudo-random’ scanning paths of laser beam. The influence of process parameters on the build height of thin-walled metal parts was studied by 1–10 layered single-bead stacks of nickel alloy. The result shows that the interference factors which affect the build height of thin-walled metal parts occur randomly during the process. For open-loop DLF process, thin-walled metal parts can achieve much better shape quality if the process parameters are suitable. Multilayer single-bead walls were built up with different scanning velocity to obtain the optimal process parameters of thin-walled parts of nickel alloy. It shows that thin walls of nickel alloy with uniform height can be built up layer by layer in a certain range of specific energy. However, it is difficult to control the build height of complex thin-walled metal parts in an accurate manner just using optimal parameters. A special coaxial powder nozzle was designed in this paper. In a certain range, the deposition thickness of the nozzle is nearly linearly increased with increase in the standoff distance between the powder focusing point of the nozzle and the deposition substrate. By means of the nozzle, a novel method to control the build height of thin-walled metal parts using open-loop DLF process was introduced. The difference in build height of a thin-walled part can be compensated automatically in one or several layers during the process. It is proved that the build height of a thin-walled metal part can be accurately controlled in theory using the nozzle. A complex single-bead part of nickel alloy whose geometry was designed to be the well-known Chinese ‘FU’ was fabricated and explained in this paper. The result shows that the shape quality of the sample is quite good, and actual build height of the sample is 53.54 mm while the designed value is 54 mm.     

低压铸造ZL114A合金微观组织的研究与数值模拟

通过浇注阶梯试样对低压铸造ZLll4A合金进行了试验研究，分析了不同冷却速率对合金凝固过程的影响。基于试验数据统计分析，建立了形核模型，并给出了模型相关热力学、动力学参数。结果表明，随着冷速的增加，液相线温度、形核温度和共晶转变温度均降低，初生相以及共晶相的形核、凝固时间缩短。采用了一种改进的Celluar Automaton方法，耦合有限差分法对合金的宏观凝固及微观组织演化过程进行了数值模拟。对航空启动机叶轮不同部位的微观组织进行了预测并将模拟值与试验值进行了对比验证，试验和模拟值吻合较好。     

Biodegradable polyester blends for biomedical application

A new family of bioabsorbable materials suitable for biomedical applications was designed and prepared by means of blending of some available polyesters to develop new biodegradable materials tailored for different requirements. Multiphase polymer blends containing poly(d, l-lactide) (PLA), poly(ε-caprolactone) (PCL), poly(d, l)-lactide-co-poly(ethylene glycol) (PELA), poly(ε-caprolactone) -co-poly(ethylene glycol) (PECL), and poly(ß-hydroxybutyrate) (PHB), PLA/PCL, PELA/PECL, PHB/PLA, PHB/PELA, PHB/PCL, and PHB/PECL blends were respectively investigated. It was found that PLA/PCL, PHB, and PHB/PLA and PHB/PCL blends were seemingly immiscible, with their morphology and hydrolytic behavior were determined by the composition of the blends. On the other hand, the miscibility of PELA/PECL, PHB/PELA, and PHB/PECL blends was improved by using PELA and/or PECL block copolymers that contained poly(ethylene glycol) (PEG) as compatibilizer. The blends showed to a certain extent miscibility, fine phase morphology, and fast hydrolysis. © 1995 John Wiley & Sons, Inc.     

纳米Mg—Ni合金吸／放氢过程的热力学性能研究

采用机械合金化法制备了Mg-Ni合金粉末。用XRD及SEM等手段分析表征了球磨过程中的相和微观结构变化，测定了纳米Mg-Ni合金吸／放氢过程的热力学性能。结果表明，Mg-Ni合金粉末的尺寸在10nm-20nm之间；P-C等温线存在明显的坪曲线，坪宽较长。纳米Mg-Ni合金有较好的储氢性能，具有很好的工程应用价值。     

低成本钛合金制备技术研究进展

为了降低钛合金的生产成本,美、俄、日、中等国家都在此领域进行了广泛的研究。对国际上新出现的以降低钛合金生产成本为目的的新冶金方法、新的低成本合金化钛合金和新的加工生产技术进行了综述。目前,国际上研究较为活跃的低成本钛冶炼新方法有FFC剑桥法、Armstrong工艺、EMR复合阳极工艺、SRI工艺、Idaho钛工艺及OS工艺。其中,以FFC剑桥法为代表的TiO2直接电解还原方法,最有希望成为替代传统Kroll工艺的新方法。     

干混合对硬质合金组织结构的影响

采用扫描电镜,通过对WC原料粉末、脱蜡压坯断口与表面、合金抗弯强度样品断口与合金烧结体表面微观形貌以及合金金相组织的观察,研究了干混合对硬质合金组织结构的影响。结果表明,干混合只对压坯成形过程中粉末颗粒的压制行为与烧结过程中合金的致密化行为产生影响,不会对烧结过程中的合金化行为产生影响。压坯中的大孔洞与未压好等压制缺陷以及显著的元素分布不均匀现象难以通过液相烧结得到有效消除,会继续保留至合金中。采用干混合工艺制备合金,合金晶粒均匀、粗大,接近原料粉末的电镜观测粒度。     

金属陶瓷多弧离子镀TiN／TiAlN涂层的结构与性能

采用多弧离子镀技术在Ti（C，N）基金属陶瓷基体上沉积了TiN／TiAlN涂层，通过扫描电镜、能谱仪、X射线衍射仪、原子力显微镜等分析技术对其显微组织、成分、相结构、粗糙度及涂层与基体间的结合强度进行了分析。结果表明，多弧离子镀TiN／TiAlN涂层后试样的表面为金黄色，涂层光滑平整，其均方根粗糙度为20．6nm，显微硬度达到2808HK。TiN相和TiAlN相均存在强烈的（111）择优取向。Al的含量从涂层内部到表面逐渐增大，呈现梯度分布特征。TiN／TiAlN涂层与金属陶瓷之间的结合强度高达57．52N。