K.H.W.Seah(Dept. of Mechanical Engineering
,
National University of Singapore
,
10 Kent Ridge Crescent
,
Singapore 119260)R.S.Kulkarni and S.C.Sharma (Dept. of Mechanical Engineering
,
R.V.College of Engineering
,
Mysore Road
,
Bangalore-560-059
,
Karnataka
,
Ind
材料科学技术（英文）
This paper reports some results obtained in an investigation to see how increasing the corundum dispersoid content from 0% to 7% in a matrix of as-cast and wrought hiduminium alloy affects the hardness. wear resistance and fracture toughness of the composite. The results show that as the corundum content is increased, the hardness and the wear resistance increase remarkably,whereas the fracture toughness drops significantly. It was found that Just a minute amount of corundum is sufficient to cause a fairly large change in these mechanical properties. The hardness of the material is also affected signifIcantly by the aging time. Moreover, if other factors are kept constant, hot extrusion improves both its hardness and its wear resistance. whereas the fracture toughness is decreased
关键词:
K.H. W. Seah(Dept. of Mechanical Engineering
,
National University of Singapore
,
10 Kent Ridge Crescent
,
Singapore 0511)R.S.Kulkari and S.C.Sharma (Dept. of Mechanical Engineering
,
R.V.College of Engineering
,
Mysore Road
,
Bangalore-560-059
,
Karnataka
,
Indi
材料科学技术（英文）
This paper reports some results obtained in an investigation to see how increasing the corundum dispersoid content from o% to 7% in a matrix of hiduminium alloy affects the tensile and compressive strengths, the hardness and the casting characteristics of the composite. The results show that as the corundum content is increased, ultimate tensile strength (UTS)- compressive strength and hardness increase remarkably, whereas fluidity of the molten composite during casting drops significantly. It was found that just a minute amount of corundum is sufficient to cause a fairly large change in the mechanical properties and the fluidity of the molten material.This drop in castability is one of the reasons why adding corundum beyond 7 percent is not recommended. If other factors are kept constant, the fluidity is seen to slightly improve if the pouring temperature of the molten metal were increased from 670 to 710℃
关键词:
Dong LI
,
Zhentao YU
,
Weisheng TANG
,
Ju DENG
材料科学技术（英文）
NIN has developed a new type of Ti alloy. It is suitable for structure pieces applied in high-temperature and high-pressure water/steam conditions. Its nominal composition is Ti-4Al-2V. In this paper, its microstructure, mechanical properties and corrosion resistance were studied in detail.
关键词:
Communications in Theoretical Physics
The mistakes in Ref. [3] are pointed out. Some important problems are discussed, and the correct ideas, calculations and results are given. The R-line thermal shift of MgO:V2+ at normal pressure is the algebraic sum of the contribution from electron-phonon interaction and the contribution from thermal expansion. The latter can be calculated by using the thermal expansion coefficient and the pressure-induced shift.
关键词:
R-line thermal shift of MgO : V2+;pressure;temperature
Communications in Theoretical Physics
A great improvement on a previous work (Phys, Rev. B48 (1993) 14067) has been made. By taking into account all the irreducible representations and their components in the electron-phonon interaction (EPI) as well as all the levels and the admixtures of basic wavefunctions within d(3) electronic configuration, the values of all the parameters in the expressions of thermal shift (TS) and thermal broadening (TB) from EPI for the ground level, R level and R line of MgO:V2+ have microscopically been evaluated; and then, both the TS and TB of R line and various contributions to them have uniformly been calculated. The results are in very good agreement with the experimental data. It is found that all the three terms of TS from EPI are red shifts; the term of the contribution to TS from thermal expansion is blue shift. The Raman term is the largest, and the other terms are also important for TS. The R-line TS of MgO:V2+ comes from the first-order term of EPI. The elastic Raman scattering of acoustic phonons plays a dominant role in R-line TB of MgO:V2+. For calculations of both the TS and TB, it is very important to take into account all the admixtures of wavefunctions.
关键词:
crystal fields;optical properties;electron-phonon interaction;electronic structure;thermal shift and broadening;thermal expansion;pressure-induced shifts;energy-spectrum;sharp lines;ruby;temperature;mgo;v2+
Journal of Physics-Condensed Matter
Using x-ray diffraction, powder neutron diffraction, high-field magnetization measurement and thermomagnetic analysis, we have studied the structural and magnetic properties of RFe(10)V(2)C(0.5) alloys (R = Sm or Y) made by are melting, in which the carbon was added using Fe-C alloy. Both samples are found to be nearly single phase with ThMn12-type structure and with a small amount of alpha-Fe phase (less than 4 wt%). The neutron diffraction of the Y-containing compound indicates that the real composition of the main phase is Y(Fe9.87V1.90C0.23)C-0.27. and that the carbon atoms occupy not only the interstitial 2b site but also the substitutional 8i site. The Fe moments of the 8i site as well as the 8j site are found to be reduced in the Y(Fe9.87V1.90C0.27)C-0.27 compound compared with its carbon-free counterpart. The decrease in the Fe moment at the 8j site is due to the surrounding interstitial carbon atoms, while the decrease in the Fe moment at the 8i site is ascribed to the surrounding substitutional carbon atoms as nearest neighbours. The high-field magnetization measurements indicate that the anistropy held of SmFe10V2C0.5 and YFe10V2C0.5 are slightly higher than those of SmFe10V2 and YFe10V2, respectively. In SmFe10V2C0.5, the magnetization curve in the hard direction at 4.2 K shows a first-order-magnetization-process (FOMP)-like or quasi-FOMP-like transition.
关键词:
intermetallics;y(fe11ti);nitride;metal;gd;tm;c)
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
