B/Ti Atomic Ratio and Al Content on Microstructure and Properties of New Neutron Absorbing Austenitic Stainless-Steel Composites

Metallurgical and Materials Transactions A - A new type of austenitic stainless-steel composite with different B/Ti atomic ratios and Al contents have been fabricated by in situ synthesis...     

原位反应合成致密Al2O3p-TiCp/Al复合材料

采用高能球磨细化晶粒、原位反应合成及热压技术制备了致密的Al2 O3 p TiCp/Al复合材料 ,并用XRD、SEM、以及EDAX等手段分析了复合材料的相组成、显微组织。结果表明 :Al TiO2 C三元体系在热压反应烧结后 ,可制得致密度较高的Al2 O3p TiCp/Al原位复合材料 ,其显微组织中Al2 O3 和TiC颗粒尺寸为 1μm左右 ,分布均匀。高能球磨有利于增强颗粒细化及弥散分布和反应。     

Synthesis of In Situ SiC/Graphite/Al Hybrid Composite Coating by Laser Direct Energy Deposition

Metallurgical and Materials Transactions A - The present work is undertaken to highlight a novel in situ process to fabricate SiC/graphite/Al hybrid composite coating by laser direct energy...     

Effects of Gd Addition on the Hot Deformation Behaviors of B4Cp/Al6061 Neutron Absorber Composites

Metallurgical and Materials Transactions A - B4Cp/Al6061 composites with and without Gd addition fabricated by ultrasound-assisted casting method were subjected to hot compression tests...     

喷射沉积SiCP/Al复合材料及6066铝合金热挤压工艺的研究

作者应用喷射共沉积工艺制备 6 0 6 6 / Si Cp复合材料和 6 0 6 6铝合金锭坯 ,在不同的挤压比、挤压温度下挤压成　　型 ,用金相显微镜观察材料的显微组织 ,并测试了材料的力学性能。结果表明 :Si C/ Al复合材料喷射沉积状态的组织很疏松 ,存在许多的间隙 ,其密度约为理论密度的 86 % ,Si C颗粒在复合材料中分布不均匀 ,喷射沉积铝合金基体的致密度可达 90 % ;挤压过程使 Al/ Si Cp复合材料的大多数空隙消失 ,致密程度随挤压比的增大而增大 ,挤压比超过 14 .7后不会明显变化 ,而铝合金基体的致密程度与挤压比的变化关系不明显 ;挤压温度对材料的致密程度影响不大 ;Al/ Si Cp复合材料性能在挤压比超过 14 .7后变化不大 ;铝合金的性能不受挤压比变化的影响 ;而挤压温度过高使材料性能下降     

Fabrication of SiC-Particles-Shielded Al Spheres upon Recycling Al/SiC Composites

Wettability of liquid A359 alloy on SiC particles under molten salt NaCl-KCl-NaF is found at 180 deg, meaning that SiC particles prefer the molten salt phase against the Al phase or the Al/molten salt interface. Thus, this molten salt can be used for recycling, i.e., to separate the phases in the SiC reinforced Al matrix composites. If the separation process is interrupted, Al droplets (submillimeter solidified powder) can be produced, stabilized/surrounded by a monolayer of shielding SiC particles.     

Microstructural and Phase Composition Differences Across the Interfaces in Al/Ti/Al Explosively Welded Clads

The microstructure and phase composition of Al/Ti/Al interfaces with respect to their localization were investigated. An aluminum-flyer plate exhibited finer grains located close to the upper interface than those present within the aluminum-base plate. The same tendency, but with a higher number of twins, was observed for titanium. Good quality bonding with a wavy shape and four intermetallic phases, namely, TiAl₃, TiAl, TiAl₂, and Ti₃Al, was only obtained at the interface closer to the explosive material. The other interface was planar with three intermetallic compounds, excluding the metastable TiAl₂ phase. As a result of a 100-hour annealing at 903 K (630 °C), an Al/TiAl₃/Ti/TiAl₃/Al sandwich was manufactured, formed with single crystalline Al layers. A substantial difference between the intermetallic layer thicknesses was measured, with 235.3 and 167.4 µm obtained for the layers corresponding to the upper and lower interfaces, respectively. An examination by transmission electron microscopy of a thin foil taken from the interface area after a 1-hour annealing at 825 K (552 °C) showed a mixture of randomly located TiAl₃ grains within the aluminum. Finally, the hardness results were correlated with the microstructural changes across the samples.

     

Hydrogen Embrittlement Processes and AL／AL2O3 Hydrogen Resistance Coatings of NdFeB Magnets

After analyzing the phenomena and processes of hydrogen embrittlement of NdFeB permanent magnets, RF magnetron sputtering was used to fabricate A1 thin films and then oxidized to form the Al/Al2O3 composite films on the magnets as the hydrogen resistance coatings. SEM and EDS were used to examine the morphology and composition respectively. Hy-drogen resistance performance was tested by exposing the magnets in 10 MPa hydrogen gas at room temperature. The results show that the magnets with 8μm Al/Al2O3 coatings can withstand hydrogen of 10 MPa for 65 min without being embrittledinto powd er. The samples with and without hydrogen resistance coatings have almost the same magnetic properties.     

7050Al/Gr复合材料的组织及力学性能

为获得一种力学性能和阻尼性能俱佳的材料,在7050Al合金基体中加入4％（体积分数）的石墨（Gr）作为增阻体,用包套挤压的方法制备7050Al/Gr复合材料,研究石墨的加入对7050A1合金组织和力学性能的影响。结果表明加入石墨后,时效过程中沉淀相析出长大速率加快,峰时效时间提前约4h,峰时效强度和硬度都有所降低。7050A1／Gr复合材料峰时效强度（吼）和硬度（HB）分别为521MPa和152,而7050Al合金峰时效强度和硬度分别为558MPa和158。     

Al/SiC复合材料激光快速成形的研究

激光快速成形技术制备Al/SiC复合材料基于快速成形原理，通过激光熔化同轴输送的Al/SiC复合粉末，在基板上直接成形出薄壁样品。鉴于Al/SiC复合粉末的特点，采用基板预热并预涂覆吸光涂层以降低所需的激光功率，避免铝的过度熔化和SiC的分解。所制得的Al/SiC复合材料组织均匀、细小，SiC分解量很少且分布均匀，有少量的Al4C3,Al4SiC4及单质硅生成。     

Investigation of Production and Abrasive Wear Behavior of Functionally Graded TiB 2 /Al and TiB 2 /Al–4Cu Composites

In this study, it is aimed to investigate the production and abrasive wear properties of functionally graded TiB2/Al and TiB2/Al–4Cu composites. Using in situ technique, titanium di-boride (TiB2) particles are being spontaneously formed in liquid matrix, resulting in a “Al(l) + TiB2(S)” semisolid at 900 °C. The semisolid solidifies under a centrifugal force at 1500 rpm rotation speed in a steel mold to produce functionally graded composites. The properties of composites such as density, abrasive wear, hardness and microstructure were examined by dividing into four zones from the outside to the inside of the composite. Volume loss of composites were examined by using L16(4124) orthogonal design, considering some factors such as matrix type of composites, region of composites, abrasive particle size, sliding speed and sliding load according to Taguchi method. The results showed that both TiB2/Al and TiB2/Al–Cu composites had two regions: the TiB2-reinforced and non-reinforced regions. It was determined that the volume loss increased with increasing load, speed and abrasive particle size and decreased with increasing TiB2 particles reinforcement ratio.     

机械合金化Ti/Al合金的制备

采用多维摆动式球磨机机械合金化Ti/Al二元粉末,研究了机械合金化过程中粉末结构的变化。Ti/Al混合粉末经高能球磨后,颗粒尺寸下降,Ti、Al晶粒各自逐渐细化至纳米级尺寸,且部分形成非晶,球磨15h后发现了TiAl和Ti3Al金属间化合物。将机械合金化后的粉末进行放电等离子烧结,烧结试样的组成相主要为TiAl和Ti3Al。     

Micromechanical Investigation of the Fatigue Crack Propagation and Damage Development in Al/Al2O3/SiC Hybrid Metal Matrix Composite

Russian Journal of Non-Ferrous Metals - In this study, the micro-mechanisms involved in fatigue crack propagation are investigated qualitatively in a Al/Al2O3/SiC hybrid metal matrix composite...     

Roll-Bonded Tri-Layered Mg/Al/Stainless Steel Clad Composites and their Deformation and Fracture Behavior

The deformation and fracture behaviors of roll-bonded tri-layered Mg/Al/stainless steel (SST) composite plates were studied. Brittle interfacial reaction compounds were observed at the Mg/Al interface upon annealing at and above 573 K (300 °C), whereas no visible interfacial reaction compounds were observed at Al/SST interfaces even after annealing up to 673 K (400 °C). The strength of the tri-layered Mg/Al/SST clad plates is in close agreement with those calculated from the strength data of the separated Mg, Al, and ST layers using the rule of mixture. The fracture strain components of the tri-layered clad in the absence of brittle interfacial intermetallic layer far exceed those calculated based on the fracture strain data of separated Mg, Al, and SST sheets. The enhanced ductility of the clad composites is due to the suppression of the localized deformation in a metallic layer by other metallic layers caused by the mutual constraint imposed by an adjacent layer. On the other hand, the fracture strain was found to be reduced in the presence of intermetallic layers between the metallic substrates. Cracks perpendicular to the stress axis were observed in the intermetallic compound layer between Mg and Al, inducing the localized slip in the vicinity of intermetallic cracks and premature fracture of the Mg alloy layer.     

包裹型SiO2/Al复合粉体的制备及烧结性能研究

为了克服金属陶瓷两相分布不均、界面不润湿和难以烧结致密等难题,采用球磨技术将增强相均匀包裹在基体材料表面,研究包裹型SiO₂/Al复合粉体的球磨制备工艺及其烧结性能,提高金属陶瓷的综合性能。结果表明,随着球磨时间的延长,SiO₂/Al复合粉体的比表面积先增大后减小,球磨6 h获得的复合粉体比表面积最大,达到8.1 m2·g?1。随着球料比的增大,SiO₂/Al复合粉体的比表面积先增大后减小,说明SiO₂包裹在Al粉表面的量呈现先增多再减少的趋势。随着球磨转速的增大,SiO₂/Al复合粉体比表面积先增大后减小。随着烧结温度的提高,SiO₂/Al金属陶瓷表面硬度先增高后降低,在烧结温度为900 ℃时,SiO₂/Al金属陶瓷的表面硬度达到最高。球磨时间为6 h,球料比为2:1,球磨转速为360 r·min?1,烧结温度900 ℃可以获得性能较佳的SiO₂/Al金属陶瓷。     

Growth characteristics of directionally solidified Al203/YAG/ZrO2 ternary hypereutectic in situ composites under ultra-high temperature gradient

Oxide eutectic ceramic in situ composites have attracted significant interest in the application of high-temperature structural materials because of their excellent high-temperature strength,oxidation and creep resistance,as well as outstanding microstructural stability.The directionally solidified ternary Al_2O_3/YAG/ZrO_2 hypereutectic in situ composite was successfully prepared by a laser zone remelting method,aiming to investigate the growth characteristic under ultra-high temperature gradient.The microstrucnrres and phase composition of the as-solidified hypereutectic were characterized by using scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),and X-ray diffraction(XRD).The results show that the composite presents a typical hypereutectic lamellar microstructure consisting of fine A1203 and YAG phases,and the enriched ZrO_2 phases with smaller sizes are randomly distributed at the Al2O3/YAG interface and in Al_2O_3 phases.Laser power and scanning rate strongly affect the sample quality and microstructure characteristic.Additionally,coarse colony microstructures were also observed,and their formation and the effect of temperature gradient on the microstructure were discussed.     

Al2O3/AlTiC/ZrO2/透辉石陶瓷材料的力学性能及微观结构

将金属Al、Al3Ti和TiC以AlTiC中间合金的形式以及ZrO2颗粒共同引入Al2O3基体材料中,热压制备了Al2O3/TiC/ZrO2/AlN复合材料.在此基础上,添加(体积分数)1%透辉石作为烧结助剂,以实现复合材料的液相烧结并促进其致密化程度.复合材料在烧结过程中有新相AlN生成;同时Al、TiC以及Al3Ti释放的Ti原子发生原子重组生成Al2Ti4C.对热压后材料的硬度、断裂韧度和抗弯强度进行了测试和分析;探讨了透辉石对材料致密化程度及力学性能的影响效果;研究了复合材料断面断裂方式的变化对其力学性能的影响;并对AlTiC中间合金的细化特性进行了分析.     

CA-MIG热源处理下钛/铝异质合金界面显微组织特性

采用Al-Si5焊丝进行TC4钛/1060铝异质结构的CA-MIG连接,采用SEM、EDS等显微分析手段对不同热输入下所获接头的Ti/Al界面显微组织特点、界面附近元素分布进行分析,研究Ti/Al界面特性随热源热输入变化的演变规律。结果表明,CA-MIG热源热输入对Ti/Al界面显微组织具有显著影响。当热源热输入低于0.91 kJ/cm时,钛与铝基焊缝之间仅形成了一层界面反应层。当热源热输入处于0.91~1.55 kJ/cm时,钛与焊缝之间形成了两种Ti/Al界面,一种为单层结构的齿状Ti(Al,Si)₃;另一种由α-Ti(Al,Si)均匀层、Ti₅Si₃纳米颗粒+Ti(Al,Si)₃混合层、齿状Ti(Al,Si)₃层3层结构组成。当热源热输入超过1.55 kJ/cm后,除了上述两种Ti/Al界面外,局部微区钛合金发生熔化,与铝基焊缝之间形成了成分复杂的熔合区,熔合区内存在大量的裂纹缺陷。     

原位还原法制备Al/Al2O3复合材料的力学性质及反应动力学

以石英为先驱体,以液态铝为还原剂,在1073～1523 K的温度范围内对原位生成铝/氧化铝复合材料进行了研究,对获得的复合材料的物理和机械性能做了测定,并对材料显微结构进行了观测和分析.在1473K制备的铝/氧化铝复合材料密度为2.95g/cm3,最大弹性模量为130 GPa,最大三点抗弯强度为580 MPa,最大拉伸强度为268 MPa,洛氏硬度为86.产物铝/氧化铝复合材料的形状与作为先驱体的二氧化硅的形状几乎一致.讨论了反应过程的动力学.