混合实验法在W-Ni-Cu合金组分设计中的应用

采用极端顶点设计法设计W-Ni-Cu合金组分,将组分自变量与相对应的性能因变量(相对密度、显微硬度、抗弯强度)进行回归分析和规划求解,同时采用冷压烧结法制备不同组分的W-Ni-Cu合金,测定合金的密度、显微硬度和力学性能,研究组分对合金性能的影响。结果表明:回归方程复相关系数R~2=1,方程精确度高;合金性能随组分变化而呈规律变化;当Ni含量与Cu含量(均为质量分数)分别为3%和5%时,合金的综合力学性能最佳:相对密度为94.295%、显微硬度286.55、抗弯强度931.51 MPa。W-Ni-Cu合金的相对密度计算值与实验结果的误差为-0.45%~0.06%,显微硬度计算值与实验结果的误差为-8.48%~4.46%,抗弯强度计算值与实验结果的误差为-5.19%~4.15%。误差很小,说明混合实验和极端顶点设计法能优化W-Ni-Cu合金组分,并可靠预测合金性能。     

Mechanical alloying and field assisted hot pressing of nanocrystalline B2-NiAl intermetallic compound

Abstract

Ordered B2-NiAl intermetallic compound powder was successfully synthesised by mechanical alloying after 20 h in an attritor mill, starting from elemental Ni and Al powders and without subsequent heat treatment. NiAl powder obtained was homogenous and had a nanocrystalline microstructure. It was consolidated by field assisted hot pressing (FAHP), in a novel configuration with a Gleeble 3800 thermomechanical simulator. The powder was also processed by hot isostatic pressing (HIP) in order to compare both methods. The consolidation was successful by both methods obtaining above 98% of NiAl theoretical density (5·86 g cm^?3). The results showed that the consolidation process by FAHP technique is effective and uniform throughout the sample as indicated by homogenous hardness values, obtaining microstructure and properties similar to those obtained with HIP technique, with certain advantages over it. The achieved room temperature yield strength of 850 MPa and fracture strain 26–28% corresponds to the bulk values of NiAl intermetallic.     

Effect of hot isostatic pressing (HIP) on Al composite parts made from laser consolidated Al/Fe2O3 powder mixtures

Selective laser melting (SLM) was used to manufacture Al composite parts from Al/5–15 wt%Fe₂O₃ powder mixtures and followed by hot isostatic pressing (HIP) post-treatment, in order to assess the influence of HIP on density, hardness and microstructure. It was found that the HIP post-treatment slightly increased the density, but it failed to efficiently densify the material due to formation of thick oxide bands between solids within SLM process, expanding with increasing the iron oxide. The hardness also decreased after HIP, attributed to high temperature annealing impact of HIP post-treatment on microstructure (such as coarsening, coalescence and transformation of phases). The microstructural phases before HIP were a combination of equilibrium and stable phases (i.e. Al₁₃Fe₄ and α-Al₂O₃) plus phases such as Al₂Fe, AlFe, Fe₃Al, and intermediate-Al₂O₃ (formed in high Fe₂O₃ contents), but only equilibrium and stable phases remained after HIP post-treatment.     

耐火材料等静压戊形缺陷分析与预防措施

详细介绍了数值模拟技术在耐火材料等静压成形分析中的应用，分析并讨论了耐火材料在等静压成形过程中的各种缺陷产生的原因及其防止办法。     

Grain refinement in low SFE and particle-containing nickel aluminium bronze during severe plastic deformation at elevated temperatures

The influence of particle size and morphology on grain refinement in low stacking fault energy(SFE)alloys was studied by comparing the grain structures in single-and multi-phase Al-bronze(AB)alloys following equal channel angular pressing(ECAP)between 350 and 500℃.In particular,nickel aluminium bronze(NAB)was chosen as it contained both coarse and fine rounded particles,as well as a lamellar phase which evolved during ECAP.Grain refinement in the single-phase alloy was achieved through dynamic recrystallisation initiated at deformed twin boundaries.By contrast,different mechanisms were observed in the particle-containing NAB.Recrystallisation around the coarse κⅡ particles(～5 μm)was promoted through particle stimulated nucleation(PSN),whereas recrystallisation in the region of the fine κⅣ(～0.4μm)was delayed due to the activation of secondary slip.Grain refinement in areas of the lamellar κⅢ showed significant variation,depending on the lamellar orientation relative to the shear plane of ECAP.As the lamellae deformed,numerous high angle grain boundaries were generated between fragments and served as nucleation sites for recrystallisation,while PSN occurred around spheroidised lamellae.The spreading of the κⅢ particles by ECAP then enhanced the total area of recrystallised grains.     

Tape casting coupled with isostatic pressing as an alternative fabrication method for microtubular solid oxide fuel cells

A new production technique consisting mainly of a combination of tape casting and isostatic pressing to fabricate microtubular supports for solid oxide fuel cells is presented in this study. For this purpose, thin anode support layer is obtained by tape casting. The tape is then wrapped around a rod and subjected to isostatic pressing. The anode support microtube laminate is sintered after the removal of the rod. Microstructural observations show that the anode support with the suggested method is free of delamination and structural defect. Similar microtubular supports are also fabricated by conventional extrusion to compare the mechanical performance. Three point bending test results indicate that the anode supports with the suggested method provide higher mechanical strength due to improved compaction by isostatic pressing. Furthermore, similar microtubular cells are constructed on both anode supports for the electrochemical considerations. The results reveal that the cell, whose anode support is manufactured via tape casting and isostatic pressing, provides a reasonable electrochemical performance although no optimization is carried out in the fabrication steps. Therefore, the method recommended in this study is found to be an appropriate method for the fabrication of tubular/microtubular supports in solid oxide fuel cells or in similar areas.     

Evaluation of percentage oil yield,energy requirement and mechanical properties of selected bulk oilseeds under compression loading

The present study examined the percentage oil output, energy and mechanical properties of selected bulk oilseeds namely pumpkin, hemp, sesame, milk thistle, cumin and flax by a uniaxial compression process of a maximum load capacity of 500 kN and a preset speed of 5 mm/min. Each sample was measured at 60 mm pressing height with a plunger using the pressing vessel of diameter 60 mm. The results show that milk thistle seeds required the highest force corresponding to the highest stress and energy demand for recovering the oil in both the bulk oilseeds and seedcakes. However, pumpkin seeds produced the maximum residual oil yield of 24.99 ± 0.04%, followed by sesame seeds at 21.29 ± 1.82% and then flax seeds at 22.61 ± 0.31%. The study revealed that higher energy is required to produce the maximum oil yield with minimum residual oil in the seedcake by continuous pressing.     

钨粉化学镀铜对压制性能的影响

通过钨粉表面化学镀铜,使其表面包覆一层均匀的诱导铜膜,以此制备W-15Cu电子封装材料。采用扫描电镜和双对数压制方程理论分析,研究钨粉表面化学镀铜含量对钨粉压制性能的影响,结果表明钨粉表面化学镀铜可改善其压制性能,且随化学镀铜含量的增加,压制同等生坯密度的制品压力增大。     

Experimental based full process simulation of alumina selective laser processed parts densified by cold isostatic pressing and solid state sintering

The compound process of cold isostatic pressing (CIP) of alumina selective laser processed (SLP) parts and solid state sintering (SSS) and its full process simulation were realized in this paper, focusing on studying the overall deformation, relative density distribution, grain growth and sintering stress variation during the process. Especially, correlation was established between the macroscopic deformation and microscopic evolution. Model parameters for alumina are presented, which were optimized in accordance with the experimental results. CIPed part still exhibited density inhomogeneity, of which SSS tended to increase the overall density and homogenize density distribution. The sintering behavior was studied with the employment of dilatometer experiments. Furthermore, compared with conventional heating strategy, fast firing turned out to decrease sintering production time as well as drive the matter diffusion and densification process. The master sintering curve (MSC) moves upward a little under the condition of fast firing.     

A new method for manufacturing graded refractories by localized hot uniaxial pressing

In this study, a cylinder of fine-grained carbon-bonded alumina was pressed uniaxially at high temperatures in an argon atmosphere. The resulting changes in mechanical properties, physical properties and microstructure were described with various techniques. The porosity of the material was found to have decreased significantly, leading to higher density, higher dynamic Young's modulus, higher strength and increased hardness. Additionally, gradients in porosity and hardness were observed that resulted from inhomogeneous temperature distribution during compression. Possibilities and conditions for the production of graded refractory materials can be deduced from the results.