Effects of TiN addition on the properties of hot pressed TiN–Ti/Al2O3 composites

TiN–Ti/Al₂O₃ composites of varying TiN content (0–20?vol%) were prepared by vacuum hot-pressing sintering at different temperatures (1400?°C and 1500?°C) to investigate how TiN affected the mechanical properties and electrical conductivity of the composites. Sintered samples with added TiN exhibited better performance than those without it. The sample with 20?vol% TiN sintered 1500?°C had an optimal relative density of 99.49, Vickers hardness of 14.94?GPa, flexural strength of 321.55?MPa, and electrical resistivity of 1474.7?μΩ?cm. However, this increased temperature did not improve the best sample resistivity of 930.3?μΩ?cm, which was obtained at 1400?°C. Form SEM images and XRD patterns, the positive effect of TiN on composite mechanical properties may be ascribed to its good performance of high hardness and strength, a decrease of the brittle intermetallic phase, the form of AlTi₃N, and the impact of the fine-grained strength of the TiN phase.     

A novel mixing method for powder metallurgy copper-carbon nanotube composites

In this study, copper matrix composite materials with different ratios of carbon nanotubes were produced. The biggest problem faced in the production of carbon nanotube-reinforced composites is that carbon nanotubes do not distribute homogeneously in the matrix. A novel mixing technique was applied to overcome this problem. Hot pressing was used in sample production. A second high-pressure densification process was applied following the hot pressing process for enhancing the properties. The properties of both the hot-pressed specimens and the specimens to which a second high-pressure densification process was applied were characterized with the density measurements, microstructure examinations, and mechanical tests. The microstructure examinations showed that carbon nanotubes could be distributed homogeneously in the copper matrix with the mixing process applied. It was found out that the high-pressure densification process applied following the hot-pressing process increased the relative density and thus, all mechanical properties.     

用于金属密封联接的自动热压封接设备研制

针对手工作业难以保证铟封工艺的质量和一致性,研制了一台自动热压封接设备,用于实现某型号精密金属器件的密封。分析了金属铟封的热压工艺过程和工艺参数;介绍了自动热压封接设备的基本结构和控制系统;详细说明了设备温度、压力等工艺参数的控制方法,并对研制设备的压力、温度的控制性能进行了测试实验。使用研制的设备进行了热压铟封实验,并对连接的可靠性和密封性能进行了测试。结果表明,热压铟封后的金属器件符合产品要求。该设备能够保证精密金属器件的封接质量和一致性,提高了铟封工艺的自动化程度,提高了生产效率。     

Densification,microstructure, elastic and mechanical properties of reactive hot-pressed ZrB2–ZrC–Zr cermets

In this study, cermets composed of zirconium diboride and zirconium carbide with intergranular zirconium were sintered by reactive hot-pressing. Relative density exceeding 97% was obtained for the sintered cermets having four distinct compositions varying in concentration of excess Zr. Their densification behaviour was examined by monitoring displacement during sintering. The microstructure was characterized by scanning electron microscopy and X-ray diffraction, and the elastic and mechanical properties were evaluated at room temperature. The effects of Zr concentration on the densification and mechanical properties were assessed. The ZrB₂ and ZrC micron-grains coarsened with increasing amount of Zr starting material. In addition, the cermets exhibited high flexural strength (546–890 MPa) and fracture toughness (6.63–10.24 MPa m^1/2), which simultaneously increased with increasing Zr concentration. However, the elastic moduli and hardness (11–18 GPa) decreased with increasing Zr. The shear modulus and Young's modulus were in the range of 150–190 GPa and 360–440 GPa, respectively.     

水热热压法制备地质聚合物

地质聚合物材料是一种新型的环保型无机复合材料,具有性能优越、价格低廉的特点.本研究采用水热热压技术,以粉煤灰、玻璃粉为主要原料,在200℃、8.5MPa的水热热压条件下制备粉煤灰基地聚合物材料.研究了不同碱激发剂的含量、浓度及玻璃粉添加量对材料抗压强度、收缩率的影响.结果表明,粉煤灰与玻璃粉的质量比为2∶1,添加25％的浓度为5 mol/L NaOH溶液时,固化体试样中有纤维状的地聚物生成,材料的抗压强度最高达到103.34MPa.     

热压工艺对SiCf/Ti复合材料界面反应层生长影响的数值模拟

提出一个热-力-扩散-反应强耦合相场模型来研究热压烧结制备工艺对连续碳化硅纤维增强钛基复合材料中金属间化合物生长规律的影响。模拟结果表明,在两种不同温度下各个界面反应层(Ti₃SiC₂/Ti₅Si₃C_x/Ti₅Si₃C_x+TiC/TiC)的厚度生长与试验值吻合较好。增大外加压力能促进界面层厚度的生长,但对其中抗拉强度最低的Ti₅Si₃层的生长起显著的抑制作用,同时使各界面反应层由周向拉应力状态逐渐转变为压应力。温度的升高使断裂韧度最大的Ti₃SiC₂层厚度增大,但也使总界面层和Ti₅Si₃层的厚度增加。因此,在制备工艺上适当增加压力并选择合适的温度,得到厚度适宜的界面反应层的同时,尽可能使Ti₅Si₃层变薄和Ti₃Si...     

In situ reaction and solid solution induced hardening in (Ti,Zr)B2-(Zr,Ti)C composites

(Ti,Zr)B₂ - (Zr,Ti)C ceramics were synthesized by reactive hot-pressing and solid solution coupling effect using ZrB₂ and TiC powders as starting materials. Effects of sintering temperature on phase relations, microstructure and mechanical properties were reported. The equimolar ZrB₂ and TiC reactants ensured a complete in situ reaction to form (Ti,Zr)B₂ and (Zr,Ti)C solid solutions. The (Ti,Zr)B₂ - (Zr,Ti)C composite sintered at 1750°C was fully densified, and exhibited a high hardness of 29.1 GPa due to fine-grain hardening and solid solution hardening. The optimized comprehensive mechanical properties such as a hardness of 27.9 GPa, a strength of 705 MPa and an indentation fracture toughness of 5.3 MPa m^1/2 were achieved in (Ti,Zr)B₂ - (Zr,Ti)C composites sintered at 1800°C for 1 hour.     

TiB2粒径对BN-TiB2复相陶瓷致密化和性能的影响

以平均粒径分别为8.1μm和12.2μm的两种TiB2粉末为原料,通过热压烧结方法制备BN–48%（质量分数）TiB2复相陶瓷,研究了TiB2粉末粒径对复相陶瓷致密化和性能的影响。结果表明：平均粒径小的TiB2粉末所制备的复相陶瓷致密化速率更快,致密度更高;在1 850℃烧结1.5 h后,表观相对密度为95.3%,体积...     

石油取芯钻头石墨模具在热压过程中的受力状况分析

石墨模具以其优良的性能被广泛应用于热压孕镶金刚石钻头的制造。本文设计了两种规格相同（直径均为216mm），但端部形状不同的石油取芯钻头的石墨模具，并利用有限元分析软件ANSYS对它们在热压过程中的受力状况进行了分析。分析结果表明：在18MPa压力下，圆弧形钻头的模具在胎体与模具接合处出现了应力集中，超过模具的极限抗拉强度，导致模具破裂。因此，在设计钻头的石墨模具时，应考虑到钻头的端部形状，参考有限元分析结果再对模具进行设计，有助于优化设计，降低试验和生产成本。     

碳纤维增强TiC陶瓷的力学性能

在2100℃,30MPa压力下,真空烧结1h制备了碳纤维体积百分数为20%的TiC陶瓷基复合材料.烧结温度的研究结果表明对于TiC复合材料而言,2100℃是比较合适的烧结温度.体积百分数20%碳纤维的加入,不但显著提高了TiC陶瓷的室温强度和断裂韧性,而且显著提高了其高温强度.复合材料的强韧化机理是纤维的桥联、拔出和裂纹偏转.