The effect of plasma spraying power on the structure and mechanical properties of hydroxyapatite deposited onto carbon/carbon composites

This paper deals with the effect of plasma spraying power on hydroxyapatite (HA) coatings on carbon/carbon composites (C/C composites). The microstructure and phase composition of the as-sprayed coatings have been examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The shear strength of the HA coatings–C/C substrates was detected on a RGD-5 tensile testing machine. Results indicate that the melting extent and the shear strength of the coatings were evidently improved with the increasing of spraying power. Moreover, the amount of decomposed phases is increased and the content of crystalline HA of coatings was slightly changed. Observation of fracture surfaces shows that carbon fiber bundles can bond well with HA coatings using 40 kW spraying power.     

Refrigerated cooling air cutting of difficult-to-cut materials

One approach to enhance machining performance is to apply cutting fluids during cutting process. However, the use of cutting fluids in machining process has caused some problems such as high cost, pollution, and hazards to operator's health. All the problems related to the use of cutting fluids have urged researchers to search for some alternatives to minimize or even avoid the use of cutting fluids in machining operations. Cooling gas cutting is one of these alternatives. This paper investigates the effect of cooling air cutting on tool wear, surface finish and chip shape in finish turning of Inconel 718 nickel-base super alloy and high-speed milling of AISI D2 cold work tool steel. Comparative experiments were conducted under different cooling/lubrication conditions, i.e. dry cutting, minimal quantity lubrication (MQL), cooling air, and cooling air and minimal quantity lubrication (CAMQL). For this research, composite refrigeration method was adopted to develop a new cooling gas equipment which was used to lower the temperature of compressed gas. The significant experimental results were: (i) application of cooing air and CAMQL resulted in drastic reduction in tool wear and surface roughness, and significant improvement in chip shape in finish turning of Inconel 718, (ii) in the high-speed milling of AISI D2, cooling air cutting presented longer tool life and slightly higher surface roughness than dry cutting and MQL. Therefore, it appears that cooling air cutting can provide not only environment friendliness but also great improvement in machinability of difficult-to-cut materials.     

轻合金覆膜砂专用酚醛树脂的开发研究

采用具有不饱和脂肪直链的EPA改性剂参与合成酚醛树脂，用不饱和脂肪直链段部分取代亚甲基键，使酚醛树脂具有高强度和较低温度分解的特性。研究了EPA的加入量对树脂性质和覆膜砂力学性能的影响，10％是最佳值。热失重试验和高温变形曲线试验结果证明，使用该树脂混制的覆膜砂，具有强度高、溃散性好等特点。实践证明：使用该种覆膜砂浇注铸件后，工人的清砂劳动量下降，工作效率显著提高。     

管道三层结构聚烯烃防腐蚀技术及应用现状

介绍了管道三层结构聚烯烃外防护技术的基本特点和技术要求，以及该技术在目前的应用情况。输气管道对耐蚀材料的需求量巨大，开发配套的粉末涂料和性能更好的改性聚烯烃树脂，是涂料市场新的增长点。     

TEM studies of cross sections of oxidized Fe-25Cr-6Al-La alloy

The oxidation behavior of the alloy Fe–25%Cr–6%Al-RE (rich in lanthanum) was investigated by means of TEM analysis. The results show that after 2 hr oxidation of the alloy, in pure oxygen at 1200° C, La precipitated in the oxide scale at the top of -Al₂O₃ grains and at the grain-boundary regions in the form of tiny particles of hexagonal La₂O₃. These tiny particles prevented aluminum from diffusing toward the surface and suppressed lateral growth of the oxide scale. The rare-earth constituents accelerated the internal oxidation of the alloy during thermal cycling between 1200° C and room temperature. They appeared as particles of aluminum oxide and lanthanum oxide. Particles of cubic La₂O₃ precipitated in the alloy matrix near the oxide scale-metal interface in a direction parallel to grain boundaries.     

STE355钢焊后显微组织中的粒贝及其对韧性的影响

研究焊接热模拟工艺参数(峰值温度Tmax和焊后冷却时间t8/5)对低碳微合金Ti—Nb钢(STE355钢)热影响区(HAZ)显微组织及冲击韧度的影响。选用干涉层腐蚀法，在光学金相显微镜下清晰显示出了显微组织中的粒贝及M—A组元。观察了Tmax和t8/5不同的热模拟试样中粒贝及M—A组元的形态及分布特征，研究了不同Tmax及t8/5参数对显微组织及冲击韧度的影响，并用电子显微镜进行了观察和验证。结果表明，热模拟峰值温度的升高，或冷却趋缓，都使显微组织变粗、韧性降低。沿晶铁素体和晶内铁素体片的长大、增厚，粒贝中块状M—A岛的长大，都对韧性的改善不利。     

基于加油时间最短的流量平衡设计方法研究

基于飞机地面压力加油系统管路模型，运用运筹学方法，建立了求取加油时间最短的数学模型，求触得出只有在流量平衡的条件下，加油时间最短。系统研究的结果验证了该结论的正确性。     

碳离子注入纯锆后在1 mol/L硫酸溶液中的腐蚀行为

为了研究碳离子注入对纯锆耐蚀性的影响,用MEVVA源对纯锆样品进行了1×1016ions/cm2至1×1017ions/cm2的碳离子注入,注入加速电压为40 kV.用X射线光电子能谱(XPS)和俄歇电子谱(AES)分析了注入样品表层元素的价态和深度分布.透射电镜(TEM)用来观察碳离子注入样品的微观结构;碳离子注入样品后相结构的变化用掠角X射线衍射(GAXRD)来检测.纯锆注入样品随后浸入1 mol/L的硫酸溶液中,测其极化曲线以评价其耐蚀性.发现碳离子注入极大地提高了纯锆基体的耐蚀行为,剂量越高,耐蚀性越好.最后,对碳离子注入导致纯锆基体腐蚀行为发生改变的机理进行了讨论.     

Si复合Al2O3-SiC材料热机械性能的研究

通过应力-应变关系、高温抗折强度等高温试验，研究了金属硅复合Al2O3-SiC材料的热机械性能，结合SEM和XRD，对金属硅复合Al2O3-SiC材料高温显微结构和物相进行分析。结果表明：金属硅作为一个组元，不仅能缓解Al2O3-SiC材料由于热膨胀系数不匹配产生的内应力，而且使Al2O3-SiC材料兼具有金属塑性的特点，从而改善了Al2O3-SiC无机材料热机械性能。     

Mn对Fe_3Al合金室温力学性能的影响

Ｍｎ对Ｆｅ_３Ａｌ合金室温力学性能的影响楼白杨，刘茂森，毛志远，涂江平，肖延龄，钟映宏（浙江大学）Ｆｅ３Ａｌ金属间化合物具有抗氧化耐腐蚀性良、比强度高和成本低等特点［１，２］，从而具有可观的工程应用前景。对这种材料目前国内研究的热点之一是改善其室温塑?..