Andrej Atrens
材料科学技术（英文）
Corrosion research by Atrens and co-workers has made significant contributions to the understanding of the service performance of engineering materials. This includes: (1) elucidated corrosion mechanisms of Mg alloys, stainless steels and Cu alloys, (2) developed an improved understanding of passivity in stainless steels and binary alloys such as Fe-Cr, Ni-Cr, Co-Cr, Fe-Ti, and Fe-Si, (3) developed an improved understanding of the melt spinning of Cu alloys, and (4) elucidated mechanisms of environment assisted fracture (EAF) of steels and Zr alloys. This paper summarises contributions in the following: (1) intergranular stress corrosion cracking of pipeline steels, (2) atmospheric corrosion and patination of Cu, (3) corrosion of Mg alloys, and (4) transgranular stress corrosion cracking of rock bolts.
关键词:
Stress corrosion cracking
,
null
,
null
Materials Science & Engineering C-Biomimetic Materials Sensors and Systems
Bamboo, one of the strongest natural structural composite materials, has many distinguishing features. It has been found that its reinforcement unit, hollow, multilayered and spirally-wound bast fiber, plays an extremely important role in its mechanical behavior. In the present work, on the basis of the study on bamboo bast fiber and wood tracheid, a biomimetic model of the reinforcing element, composed of two layers of helically wound fiber, was suggested. To detect the structural characteristics of such a microstructure, four types of macro fiber specimens made of engineering composites were employed: axially aligned solid and hollow cylinders, and single- and double-helical hollow cylinders. These specimens were subjected to several possible loadings, and the experimental results reveal that only the double-helical structural unit possesses the optimum comprehensive mechanical properties. An interlaminar transition zone model imitating bamboo bast fiber was proposed and was verified by engineering composite materials. In our work, the transition zone can increase the interlaminar shear strength of the composite materials by about 15%. These biomimetic structural models can be applied in the design and manufacture of engineering composite materials.
关键词:
bamboo;bast fiber;biomimetics;engineering composites
Science
Strengthening materials traditionally involves the controlled creation of internal defects and boundaries so as to obstruct dislocation motion. Such strategies invariably compromise ductility, the ability of the material to deform, stretch, or change shape permanently without breaking. Here, we outline an approach to optimize strength and ductility by identifying three essential structural characteristics for boundaries: coherency with surrounding matrix, thermal and mechanical stability, and smallest feature size finer than 100 nanometers. We assess current understanding of strengthening and propose a methodology for engineering coherent, nanoscale internal boundaries, specifically those involving nanoscale twin boundaries. Additionally, we discuss perspectives on strengthening and preserving ductility, along with potential applications for improving failure tolerance, electrical conductivity, and resistance to electromigration.
关键词:
strain-rate sensitivity;stacking-fault energy;nano-scale twins;cu-al;alloys;nanocrystalline metals;mechanical-properties;activation;volume;copper;deformation;behavior
QIAO Lijie LIU Rui XIAO Jimei University of Science and Technology Beijing
,
Beijing
,
China
金属学报(英文版)
The effects of stress components on nucleation sites and propagation directions of stress cor- rosion cracks in brass were investigated with specimens under mode Ⅱ and mode Ⅲ loadings. The results indicated that under mode Ⅱ loading,stress corrosion cracks nucleated on the site with maximum normal stress component and propagated along the plane perpendieular to the maximum normal stress,under mode Ⅲ loading,the stress corrosion crack was not evident on the 45°plane due to the general corrosion in aqueous solution with high NH_4OH concentra- tion,while stress corroded in aqueous solution with low NH_4OH concentration, numerous cracks with spacings of 10—150μm were found on the 45°plane with maximum normal stress and no stress corrosion cracks was observed on the plane with maximum shear stress.
关键词:
stress corrosion cracking
,
null
,
null
,
null
Metallurgical and Materials Transactions a-Physical Metallurgy and Materials Science
The half-width values of the X-ray diffraction profiles are frequently used to characterize the static strength of a strengthened surface, or the depth distribution of this mechanical parameter, in a strengthened surface layer, especially in a shot-peening affected layer. However, for the unpeened surface and the base material of the shot-peened specimen of an alloy steel treated in hard state, the experimental results shown in this article indicate that uniaxial tensile or compressive plastic deformation increases the yield strengths while it decreases the half-width values. The half-width values of the shot-peened surface and surface layer greatly decrease, whereas the yield strength of this surface remarkably increases. Accordingly, in the authors' opinion, the half-width values could not correctly describe the static strengths of hard metallic materials, and, contrary to the viewpoint put forward by a lot of researchers, the shot-peened surfaces of such materials are work hardened instead of work softened. A model demonstrating that plastic deformation reduces the half-width values by decreasing the second kind internal stresses is developed.
关键词:
张宁
,
茹红强
,
巩甘雷
,
孙旭东
,
夏鸿燕
材料与冶金学报
doi:10.3969/j.issn.1671-6620.2002.01.012
利用化学共沉淀方法制备了SiC/(Al(OH)3+Y(OH)3)陶瓷复合粉体.研究了pH值对SiC/(Al(OH)3+Y(OH)3)复合粉体的ξ电位和分散性的影响,以及pH值对Al(OH)3和Y(OH)3在SiC表面包覆性的影响.结果表明,当溶液的pH=9时,SiC/(Al(OH)3+Y(OH)3)复合粒子表面的ξ电位值较高,复合粉体的分散性和包覆效果也较好.
关键词:
共沉淀
,
包覆
,
SiC/(Al(OH)3+Y(OH)3)
,
pH值
,
ξ电位
宋杰光
,
王芳
,
徐明晗
,
杜大明
,
鞠银燕
,
李世斌
,
纪岗昌
,
张联盟
人工晶体学报
本文采用共沉淀法优化包裹型Al(OH)3-Y(OH)3/ZrB2复合粉体的合成工艺,通过TEM对合成的复合粉体进行形貌分析,得出适宜的包覆工艺参数分别是pH=9、溶液浓度为Al3+=0.017 moL/L和Y3+ =0.01 mol/L、滴定速度为0.05 ml/s、反应时间为60min.通过优化工艺,可以合成出包裹结构较好的包裹型Al(OH)3-Y(OH)3/ZrB2复合粉体,其包裹层厚度约为150 ～ 300 nm,为改善ZrB2基复合材料难于烧结致密化和高温条件下易氧化奠定原料基础.
关键词:
二硼化锆
,
合成工艺
,
共沉淀法
