材料期刊网

Induced Plasticity of a Brittle (La, Ce)-Based Bulk Metallic Glass by Surface Corrosion

Ji-Juan Liu , Ran Li , Lian-Xiang Fang , Ju Wang , Tao Zhang

金属学报(英文版) doi:10.1007/s40195-016-0368-3

Unexpected facture without any room-temperature plasticity severely limits potential structural applications of bulk metallic glasses (BMGs), especially La-, Mg- and Fe-based ones. In this study, a simple free corrosion method was provided to improve the plasticity of a brittle (La, Ce)-based BMG by the introduction of high-density corrosion defects on the surface. The influences of immersing time in 0.1 mol/L H₂SO₄ aqueous solution on the surface morphology and mechanical properties of the BMG were evaluated. With increasing immersing time from 5 to 30 min, the degree of surface corrosion increased obviously, and the distribution of corrosion defects became more homogenous. In the samples, the yielding phenomenon and certain plasticity appeared up to 0.3% after the surface treatment. The yielding and plasticity can be attributed to easier nucleation of shear bands on the defect surface rather than on the glabrous surface. The results provided a novel method to improve the plasticity of BMGs.

关键词: Metallic , glasses , Corrosion , plastic , deformation , mechanism , Rapid , solidification , Microstructure

Fabrication of Carbon Nanotube-Reinforced 6061Al Alloy Matrix Composites by an In Situ Synthesis Method Combined with Hot Extrusion Technique

Chun-Nian He , Chao Feng , Ji-Chuan Lin , En-Zuo Liu , Chun-Sheng Shi , Jia-Jun Li , Nai-Qin Zhao

金属学报(英文版) doi:10.1007/s40195-016-0376-3

Carbon nanotube (CNT)-reinforced 6061Al alloy matrix composites were prepared by chemical vapor deposition (CVD) combined with hot extrusion technique. During the preparation process, the 6061Al flakes obtained by ball milling of the 6061Al spherical powders were subjected to surface modification to introduce a hydrophilic polyvinyl alcohol (PVA) membrane on their surface (6061Al@PVA) to bond strongly with nickel acetate [Ni(II)]. Then the 6061Al@PVA flakes bonded with Ni(II) were calcined and reduced to Ni nanoparticles, which were then heat-treated at 580 °C to remove PVA for obtaining even Ni/6061Al catalyst. After that, the as-obtained Ni/6061Al catalyst was employed to synthesize CNTs on the surface of the 6061Al flakes by CVD. After hot extrusion of the CNT/6061Al composite powders, the as-obtained CNT/6061Al bulk composites with 2.26 wt% CNTs exhibited 135% increase in yield strength and 84.5% increase in tensile strength compared to pristine 6061Al matrix.

关键词: Metal , matrix , composites , (MMCs) , Microstructure , Mechanical , properties , Carbon

Hafnium in Aluminum Alloys: A Review

Zhi-Hong Jia , Hui-Lan Huang , Xue-Li Wang , Yuan Xing , Qing Liu

金属学报(英文版) doi:10.1007/s40195-016-0379-0

Lots of the available literatures on hafnium in aluminum alloys are reviewed. The new binary Al-Hf phase diagram is simply assessed. Two ternary phase diagrams including Al-Hf-Zr and Al-Hf-Sc are accounted for, with emphasis on the aluminum rich part of the diagrams. The relationship between different structure Al₃Hf and several different formation mechanisms including the probable phase transformation mechanisms is described. The continuous Al₃Hf phase particles can serve as a grain refiner in the Al melt and a precipitate for controlling the grain structure of the alloy and a strengthening precipitate. A series of effects of Fe, Si, Zr, Sc and Li addition on the behavior of Al₃Hf and Al alloys are given. Moreover, the effects of Hf on the microstructure and properties of Al alloys, such as hardness and creep, are reviewed. Finally, some views of Hf-containing Al alloys are summarized.

关键词:

Al-Hf , Phase , diagram , Al3Hf , precipitate , Microstructure , Properties

40Cr调质热处理性能不合格原因分析

肖君

物理测试

本文通过对我厂生产的40Cr钢在试验中力学性能不达标进行原因分析，从而找到操作中存在的问题，并浅析了工艺对组织、性能的影响机理。

关键词: 成分 , Mechanical capability , Microstructure , Quenching and high temperature tempering , Tempering , Hardening

多主元高熵合金AlTiFeNiCuCrx微观结构和力学性能

陈敏 , 刘源 , 李言祥 , 陈祥

金属学报

本文研究了不同Cr含量的AlTiFeNiCuCrx多主元高熵合金的微观组织和力学性能特点。结果表明，Cr含量的增加使合金的凝固模式从亚共晶向过共晶凝固转移，铸态组织由一先析出枝晶相和枝晶间的菊花状共晶组织组成。合金仅由简单的面心立方结构(富Cr相)和体心立方结构(贫Cr相)两相组成。Cr含量的增加对合金硬度的提高较小。该合金为室温脆性材料，但在1073K高温时具有很好的塑性变形能力和较高的强度，当xCr=1-1.5左右时，合金具有最优的压缩强度和塑性组合。

关键词: 多主元合金 , High-entropy alloy , Microstructure , Properties

添加硼对铸造Ti-46.5Al-8Nb合金组织和性能的影响

江治国 , 陈波 , 马颖澈 , 赵秀娟 , 刘奎 , 李依依

金属学报

研究了硼对Ti-46.5Al-8Nb合金组织的影响。研究发现硼细化了TiAl合金的晶粒尺寸，粗化了片层间距。片层间距与晶粒尺寸d-1/2符合线性关系。室温断裂强度与晶粒尺寸符合Hall-Petch关系。

关键词: TiAl合金 , Boron , Microstructure , Mechanical properties

激光立体成形Ti-20%Ni合金枝晶的组织演化

许小静 , 林鑫 , 杨模聪 , 陈静 , 黄卫东

金属学报

Ti-20%Ni(质量分数)合金激光立体成形组织由β-Ti枝晶和枝晶间(β-Ti+Ti2Ni)层片共晶及棒状共晶组成. 随着激光能量密度D　e减小, 枝晶特征尺寸F减小. 枝晶特征尺寸及共晶间距的变化规律分别与枝晶生长KGT经典模型和共晶生长TMK经典模型吻合较好.

关键词: 激光立体成形 , Parameters , Microstructure , Ti-20wt%Ni

高频脉冲电沉积镍钴合金镀层的硬度研究

许韵华曹克宁杨玉国赵宇宫晓静

中国腐蚀与防护学报

在硫酸盐电解液中，采用脉冲电源电沉积了镍钴合金。研究了电解液中CoSO₄的浓度及脉冲参数对镀层中Co含量和镀层显微硬度的影响。采用SEM和XRD研究了镀层的表面形貌和微观结构。结果表明，镀层中的Co含量对镀层硬度有显著影响，当Co含量小于55 mass%时， 镀层的硬度随着Co含量的增加递增。Co含量较低时，合金由面心立方结构（fcc）的固溶体组成。

关键词: 高频 , Ni-Co alloys , Microhardness , Microstructure

Oxygen Permeation Behaviors and Hardening Effect of Titanium Alloys at High Temperature

Hongyan MA , Maocai WANG , Weitao WU

材料科学技术（英文）

In order to improve the surface hardness and wear resistance of Ti and Ti alloy components, an oxygen permeation treatment (OPT) was developed. The oxygen permeation behaviors of three Ti alloys, TA2, TB5 and TC11, treated in air with O-P medium at high temperature have been studied. The results show that the O-P treatment can significantly improve the surface hardness of Ti alloys. The oxidation mass-gain of β-Ti alloy (TB5) is much higher than α-Ti alloy (TA2) under the same condition, while α+βTi alloy (TC11) is the lowest. All the Ti alloys treated at this condition produce two surface layers: the outer layer consists mainly of TiO¬2, as well as trace of other oxides, and the inner layer consists of a Ti-O interstitial solid solution formed by the diffusion of oxygen in α crystal lattice. Thick scales of βTi alloy (TB5) are easily formed depending mainly on the poor solid solution content of oxygen, while deep solution layer can be formed since partial β phase has been transformed into α phase. The scales of α-βTi alloy (TC11) are very thin and compact. Aluminum-rich zone, as well as deficient zone, is found in oxide layers. A crystallographic characterization of oxygen solution layer has been performed and evaluated by crystallographic lattice constant.

关键词: Microstructure , null , null , null

Microstructure and Lattice Parameters of AlN Particle-Reinforced Magnesium Matrix Composites Fabricated by Powder Metallurgy

Jie Chen , Chong-Gao Bao , Yong Wang , Jin-Ling Liu , Challapalli Suryanarayana

金属学报(英文版) doi:10.1007/s40195-015-0333-6

Magnesium matrix composites reinforced with AlN particles were fabricated by the powder metallurgy technique. The evolution of lattice constants and solid solubility levels of Al in α-Mg and the microstructure of Mg-Al/AlN composites were investigated in the present study. The results showed that the solid solubility of Al in α-Mg reached a relatively high level by the P/M process with a long time of milling. X-ray diffraction showed that the peaks of Mg phase clearly shifted to higher angles. The lattice constants and cell volume decreased significantly compared with those of standard Mg due to a significant amount of Al incorporated into α-Mg in the form of substitutional solid solution. The degree of lattice deformation decreased at a low sintering temperature and increased at higher sintering temperatures due to the presence of AlN. Microstructural characterization of the composites revealed a necklace distribution of AlN particles in the Mg matrix. Heat treatment led to precipitation of Mg₁₇Al₁₂ from the supersaturated α-Mg solid solution. The precipitate exhibited granular and lath-shaped morphologies in Mg matrix and flocculent precipitation around AlN particles.

关键词: Metal matrix composite , AlN particle , Microstructure , Lattice parameter , Powder metallurgy , Solid solubility