稀土对Al-Mg-Si系合金结构和性能的影响

本文用ＸＲＤ和ＳＥＭ方法研究了稀土对Ａｌ－Ｍｇ－Ｓｉ系合金微观结构的影响，同时还测定了这些合金的耐腐蚀及力学性能。结果表明，该体系的稀土铝合金中大约含０．１０％稀土就可以细化组织，提高使用性能。具有很好的应用前景。     

SiC陶瓷的反应合成及Ni添加剂对其合成温度的影响

利用Ｓｉ和Ｃ粉末的自蔓延高温合成反应合成ＳｉＣ陶瓷，研究合成温度对反应产物形貌和组成以及Ｎｉ添加剂对合成温度的影响。试验结果表明ＳｉＣ陶瓷的最低合成温度在１５００℃￣１６００℃之间，添加适量的Ｎｉ粉后，可以有效地降低ＳｉＣ的合成温度。     

预热对制备SHS陶瓷内衬钢管的影响

采用重力分离ＳＨＳ法制备陶瓷内衬钢管，研究了预热温度对ＳＨＳ反应过程中内衬管质量的影响。实验发现，粉末和管才预热都有助于ＳＨＳ反应和提高复合管质量。粉末预热温度过低，内衬管表面不光滑且存在大量气孔，复合管力学性能低；粉末预热温度过高，添加剂ＣｒＯ３提前分解，ＳＨＳ反应变慢，反应进行到最后阶段多余铁水和陶瓷不能从和内流出，使管头堵塞或内径变细，甚至造成废品。在本实验条件下，粉末烘干温度为１２０℃，烘     

稀土在过共晶Al-Si合金中的变质特点

采用金相显微镜、扫描电镜观察了稀土变质的过共晶Ａｌ－Ｓｉ合金中共晶Ｓｉ的形貌。结果表明：稀土在过共晶Ａｌ－Ｓｉ合金中对共晶Ｓｉ的变质不同于稀土在共晶或亚共晶Ａｌ－Ｓｉ合金中的变质作用，即在初晶Ｓｉ周围存在不完全变质组织。产生该组织特征的原因是共晶Ｓｉ在初晶Ｓｉ表面形核生长以及稀土对共晶团中α（Ａｌ）和共晶Ｓｉ两相生长的抑制作用不同。指出了在过共晶Ａｌ－Ｓｉ合金中采用稀土变质时提高冷却速度和使初晶Ｓｉ均匀分布的重要性。     

SHS-离心法制备的Fe-Cr-Ni耐蚀合金的显微组织及力学性能

ＳＨＳ（ＳｅｌｆｐｒｏｐａｇａｔｉｎｇＨｉｇｈｔｅｍｐｅｒａｔｕｒｅＳｙｎｔｈｅｓｉｓ）离心法具有高温、快速、反应过程复杂等特点，因而其产物的组织和性能也具有它的独特性。本文研究了ＳＨＳ离心法制备的ＦｅＣｒＮｉ耐蚀合金的显微组织及力学性能。     

稀土对铸铁磷共晶形态的影响

使用纯稀土合金，１号ＲＥ－Ｓｉ－Ｆｅ合金和４号ＲＥ－Ｍｇ合金作为铸铁变质剂，以检查稀土对铸铁磷共晶形态的影响，结果表明，当稀土加入量达到一定值后，铸铁中的磷共晶变得更细小和分散。含磷稀土化合物的形成和稀土促进磷在共晶团边界上更不均匀地偏聚是这种良好影响的原因，纯稀土合金的变质效果比１号ＲＥ－Ｓｉ－Ｆｅ合金更好。     

Si3N4基微米/纳米复合陶瓷微观组织

用扫描电镜和透射电镜研究纳米粉成分和含量对Ｓｉ３Ｎ４基纳米复合陶瓷组织的影响。ＳｉＣ（ｎ）／Ｓｉ３Ｎ４（μ）或Ｓｉ３Ｎ４（ｎ）／Ｓｉ３Ｎ４（μ）复合陶瓷的微观组织随纳米ＳｉＣ（ｎ）或Ｓｉ３Ｎ４（ｎ）含量的增加,基体组织逐渐变细。     

静态铝热自蔓延高温合成陶瓷涂层的研究

研究了静态铝热SHS陶瓷涂层,分析了涂层的成分、组织形态、力学性能和耐蚀性能。结果表明,添加RE或SiO₂,可以改善涂层的组织及其分布,减少孔隙,提高其力学性能和耐蚀性能。     

稀土对Al2O3陶瓷涂层组织及性能的影响

采用等离子喷涂方法制备Ａｌ２Ｏ３陶瓷涂层,研究了稀土对涂层组织及耐蚀性的影响。结果表明,在喷涂粉末中添加适当的稀土硅铁合金不仅可以改变涂层显微组织、减少和消除层状结构,而且显著提高了涂层的耐蚀性。     

稀土导电铝合金的铸态组织和相组成

本文利用光学显微镜、扫描电镜、Ｘ射线衍射仪等，研究了Ｌａ、Ｃｅ对工业纯铝铸态组织和相组成的影响。结果表明，Ｌａ、Ｃｅ能细化工业纯铝的铸态组织，并和Ｆｅ、Ｓｉ等元素结合生成了二元或三元稀土化合物相。     

热浸镀Zn-5%Al-RE合金钢丝镀层的表面形貌

本文采用金相显微镜、扫描电镜和能谱仪等设备分析了在Ｚｎ５％ ＡｌＲＥ合金溶液中热浸镀中碳钢丝表面的组织形貌和成分。通过与钢丝电镀锌和热镀锌的组织形貌对比、分析,我们发现：镀层中具有良好的过渡层组织是提高耐蚀性的根本原因。     

Effect of Rare Earth on Microstructure of Vacuum Melting Ni-Based Self-Fluxing Alloy Coatings

The Ni-based self-fluxing alloy coating containing RE was acquired by the technique of vacuum melting on the hypoeutectoid steel (Fe-0.45% C) matrix. By X-ray diffraction, SEM and EDX, the microstructure and phase structure of section of coating and the microstructure near the interface between coating and matrix were investigated, and the effect of RE on microstructure of coating was also discussed. The results show that the microstructure of the NiCrBSi alloy coating is composed of Ni-based solid solution and a lot of massive, globular and needle secondary phases CrB, Ni3B, Cr7C3, Cr23C6 among the solid solution. The metallurgical binding between steel matrix and coating is realized. RE makes needle phase of alloy coating vanish. New phases of NiB and Cr6.5Ni2.5Si are precipitated from alloy coating, and secondary phases of alloy coating are sphericized. Consequently, RE also hinders the diffusion of Ni, Cr and Si atoms from coating to matrix and Fe atoms from matrix to coating, holds back the dilution of Fe for NiCrBSi alloy coating, and assures the chemical composition of the alloy coating.     

Mechanical-indentation analysis of the microstructure and properties of plasma-sprayed ZrO2-based coatings

The relationship between the mechanical properties of plasma-sprayed thermal-barrier coatings and the properties of feedstock powders is studied. These powders have the same chemical composition and are obtained by hydroxide coprecipitation followed by air-drying and by a cryochemical method. Information on TBC failure mechanisms is used to pose and solve the problem of increasing the plasticity and, consequently, the stress relaxation coefficient of the ceramic coating. The finer structure of the cryochemical powder sprayed coating also improves its crack-resistance. The minor reduction in the hardness of the cryopowder-sprayed coating should not deteriorate the performance of the thermal-barrier coating.     

熔盐处理对 SiC 陶瓷表面及其与 Si 涂层界面性能影响研究

环境障涂层体系中粘结层与基体的结合性能是评价其质量的重要指标之一。本文针对环境障涂层中硅粘结层与硅基陶瓷材料结合性能不理想的问题,采用Na2CO3和Na2SO4熔盐作为蚀刻剂对SiC陶瓷表面进行粗糙化处理,研究了SiC陶瓷表面熔盐处理后的显微形貌、粗糙度以及物相组成。采用真空等离子喷涂技术制备了Si涂层,采用划痕法、压痕法以及拉伸结合强度测试法表征了涂层-基体界面的性能,发现采用高温熔盐处理方法可以显著提高Si涂层与SiC陶瓷之间的界面结合性能。本工作初步验证了高温熔盐处理方法是一种有效的陶瓷表面粗糙化处理技术。     

Processing of Ceramic Preforms for TRIP‐Matrix‐Composites

Metal matrix composites have been produced by conventional infiltration of ceramic preforms. The magnesia partially stabilised ceramic foams were prepared by replication method. In terms of the present paper the second process step that comprises the cold spraying of the impregnated foam is optimised. The spray coating is essential in ceramic foam production. It eliminates defects that are caused due to the squeezing process and assists to reach the critical wall thickness for acceptable mechanical properties. For this reasons the rheology of the spraying slurry and the adjustment of the spraying system have been investigated. Quality of the spray coatings was evaluated by computer tomography. The obtained ceramic foams were infiltrated by a TRIP‐steel (TRansformation Induced Plasticity) to create composite materials with improved mechanical properties. Phase composition of the composite material has been analysed using Electron Backscatter Diffraction Method (EBSD).     

Mechanism of Action of Rare Earths in High Effective Fe Powder Welding Rods

The optimum coating composition of alkali Fe powder welding rods was designed by orthogonal experiment with mix rates. A new kind of effective RE-Fe powder welding rod was prepared which could be used at the condition of direct and indirect current. The arc characteristics and stabilities of effective Fe powder welding rods containing RE were analyzed by HANNOVER analyzer. The efficiency of Fe powder welding rods was tested by weighting method. It wag found that the stability of Fe powder welding rods Wag improved when it was added with rare earths. The results of impact experiment at low temperatures and SEM analysis on impact break showed that the grain was refined, the welding joint was cleaned, and the mechanical properties of joint was enhanced with proper RE content. It was provided with good processing property for this effective RE-Fe powder welding rod, and its efficiency could arrive at 180%.     

稀土对等离子束表面冶金涂层组织的影响及热力学分析

 采用直流放电压缩电弧等离子束表面冶金技术，在Q235钢表面制备了添加混合稀土氧化物的铁基合金涂层，研究了稀土对等离子束表面冶金涂层组织的影响。结果表明：添加适量的混合稀土氧化物可有效改善冶金涂层的组织和性能。另外，采用热力学方法，分析了稀土氧化物对冶金层中夹杂物的变质作用。分析结果表明：在冶金熔池中，稀土氧化物(Ce2O3)可以被碳还原为稀土元素，这些稀土元素与氧、硫反应生成稀土硫氧化物，起到脱氧、脱硫和净化熔池的效果，从而抑制冶金层中凝固裂纹的形成。     

Influence of rare earth nanoparticles and inoculants on performance and microstructure of high chromium cast iron

The high chromium cast irons (HCCIs) with rare earth (RE) nanoparticles or inoculants were fabricated in the casting process. The phase compositions and microstructure were analyzed by X-ray diffraction (XRD) and optical microscopy (OM), respectively. The hardness and impact toughness were tested by Rockwel-hardmeter and impacting test enginery. And then, the morphology of fracture was researched by scanning electron microscopy (SEM). The results demonstrated that the phase compositions of HCCIs with addition of RE nanoparticles or inoculants which were M7C3 carbides + α-Fe did not change obviously. However, the prime M7C3 carbides morphology had great changes with the increase of RE nanoparticles, which changed from long lath to granular or island shape. When the content of RE nanoparticles was 0.4 wt.%, the microstructure of high chromium cast iron was refined greatly. The microstructure of carbides was coarser when the addition of RE nanoparticles was higher than 0.4 wt.%. The hardness and impact toughness of HCCIs were improved by addition of RE nanoparticles or inoculants. The impact toughness of HCCIs was increased 36.4% with RE nanoparticles of 0.4 wt.%, but the hardness changed slightly. In addition, the adding of RE nanoparticles or inoculants could reduce the degree of the brittle fracture. Fracture never seemed regular, instead, containing lots of laminates and dimples with the increase of the RE nanoparticles. The results also indicated that the optimal addition amount of the RE nanoparticles was 0.4%, under this composition, the microstructure and mechanical property achieved the best cooperation. In addition, through the study of erosion wear rate, when adding 0.4% RE nanoparticles into the HCCIs, the erosion wear rate got the minimum 0.32×10-3 g/mm2, which could increase 51.5% compared with that without any RE nanoparticles.     

Influence of Rare Earth on Property of Low Chromium Semi-Steel

Itisnoticeablethatthelowchromiumsemi steelhashighhardnessandabrasionresistance[1] .However,thematerialhaslowductility ,owingtothereticulatedistributionofcarbide ,whichrestrictsitsapplications .Therefore ,itisnecessarytoim provethecomprehensivepropertiesforpotentialap plications .Thecomprehensive propertiesoflowchromiumsemi steelcanbeimprovedbyaddingrareearths (RE)becauseREcanchangethemorphologyofcarbideandnon metallicinclusions ,refinegrainsize,purifyandstrengthen grainboundaryandsoon[2 -5] …