Ali Nazari
材料科学技术（英文）
In the present study, fracture toughness of functionally graded steels in crack divider configuration has been modeled. By utilizing plain carbon and austenitic stainless steels slices with various thicknesses and arrangements as electroslag remelting electrodes, functionally graded steels were produced. The fracture toughness of the functionally graded steels in crack divider configuration has been found to depend on the composites' type together with the volume fraction and the position of the containing phases. According to the area under stress-strain curve of each layer in the functionally graded steels, a mathematical model has been presented for predicting fracture toughness of composites by using the rule of mixtures. The fracture toughness of each
layer has been modified according to the position of that layer where for the edge layers, net plane stress condition was supposed and for the central layers, net plane strain condition was presumed. There is a good agreement between experimental results and those acquired from the analytical model.
关键词:
Fracture toughness
Ali Nazari
材料科学技术（英文）
In the present study, fracture toughness of functionally graded steels in crack divider configuration has been modeled. By utilizing plain carbon and austenitic stainless steels slices with various thicknesses and arrangements as electroslag remelting electrodes, functionally graded steels were produced. The fracture toughness of the functionally graded steels in crack divider configuration has been found to depend on the composites' type together with the volume fraction and the position of the containing phases. According to the area under stress-strain curve of each layer in the functionally graded steels, a mathematical model has been presented for predicting fracture toughness of composites by using the rule of mixtures. The fracture toughness of each
layer has been modified according to the position of that layer where for the edge layers, net plane stress condition was supposed and for the central layers, net plane strain condition was presumed. There is a good agreement between experimental results and those acquired from the analytical model.
关键词:
Fracture toughness
Ali Nazari
材料科学技术（英文）
Functionally graded steels were produced via electroslag remelting process using the primary electrodes of plain carbon and austenitic stainless steels. Charpy impact energy of as-prepared specimens was measured in the form of crack divider. The obtained results show that the impact energy of the specimens depends on the type and the volume fraction of the present phases. Based on the rule of mixtures, a mathematical model, which correlates the impact energy of functionally graded steels to the impact energy of the individual layers through Vickers microhardness of the layers, was presented. A good compatibility between the experimental results and those obtained from the model was observed.
关键词:
graded steels
,
Impact energy
,
Crack divider
,
Mathematical model
中国有色金属学报(英文版)
doi:10.1016/S1003-6326(16)64373-X
提出了一种从氧化铝中提取原铝的新方法。该方法的原理基于如下化学反应：AlI3+(3/2)Zn=Al+(3/2)ZnI2。首先通过氧化铝的碳热氯化反应得到氯化铝(AlCl3)，然后通过氯化铝和碘化钙的交换反应(AlCl3+CaI2→AlI3+CaCl2)得到碘化铝。在实验室条件下对这些反应进行了研究，同时对一些回收主要化学试剂的反应进行了研究(Cl2, ZnI2→Zn, CaCl2→CaI2)。采用XRD和SEM对反应产物的相组成及形貌进行分析。采用总自由能最小方法对化学反应平衡进行计算。结果表明，采用非电解方法，可以在没有非常高的温度和可消耗的化学试剂的条件下，从氧化铝中有效地提取铝。与当今采用燃煤发电提供电力的铝电解厂相比，本方法所产生的单位碳消耗和 CO2大气排放可以降低一半以上。
关键词:
铝
,
铝合金
,
氯化物
,
碘化物
,
锌
,
碘
,
高速冶金
Journal of Alloys and Compounds
Interdiffusion coefficients within the beta-phase region of the nickel-cobalt-chromium-aluminum (Ni-Co-Cr-Al) quaternary system were estimated by square root diffusivity analysis. The obtained results indicated that the cross interdiffusion coefficients D(ij) (i not equal j, i, j = Al, Cr, Co) other than D(AlCo), were less than the main interdiffusion coefficients Do (i = j), and that the values of D(Ali) were greater than those of D(Cri) and D(Coi). This finding suggests that the addition of chromium decreases the interdiffusion coefficients of aluminum and cobalt, but the addition of cobalt did not cause an obvious change in the interdiffusion coefficients of aluminum and chromium in the beta-phase region. The different effects associated with the additions of chromium and cobalt were qualitatively discussed in light of the relationship between the thermodynamic properties of the system and Wagner's interaction parameter. The results revealed that the different effects could be ascribed to the stronger thermodynamic interactions between aluminum and cobalt compared to that between aluminum and chromium. (C) 2009 Elsevier B.V. All rights reserved.
关键词:
Diffusion;NiAl phase;Electron microprobe;multicomponent diffusion couples;square root diffusivity;transfer-matrix method;zero-flux planes;intermetallic compound;coefficients;ternary;nickel;alloys;fe
陈小庆
,
孙利杰
,
邬小鹏
,
钟泽
,
傅竹西
功能材料
用MOCVD方法在Si基片上生长了Al掺杂的SiC薄膜,发现三甲基铝(TMA)源载气流量与硅烷流量之比的大小,会决定薄膜的导电类型.用XPS方法测试样品后发现,TMA载气流量与硅烷流量比直接影响Al原子在SiC薄膜中的含量.Al含量在1.5%以下,Al原子在SiC薄膜中主要以填隙形式(Ali)存在,薄膜显示出n型;而Al含量在1.5%～3%之间的时候,Al原子主要以替位Si(AlSi)的形式存在,薄膜显示出p型.继续增加掺杂源的流量,所得SiC薄膜结晶质量会变得较差,电阻也变得较高.
关键词:
3C-SiC
,
SiC:Al
,
MOCVD
,
导电类型
Acta Materialia
Porous Ni-Ti shape-memory alloys (SMAs) have attracted a great deal of attention recently because they have a similar microstructure to human bone and have significant prospects in medical applications. In the present study, equiatomic porous Ni-Ti SMAs, especially those with an unusual kind of linear-aligned elongated pore structure, have been successfully prepared by self-propagating high-temperature synthesis (SHS) using elemental nickel and titanium powders. The porous Ni-Ti SMAs thus obtained have an open porous structure with about 60 vol.% porosity, and the channel size is about 400 mu m. The corresponding microstructural characteristics and the effect of preheating temperature on the microstructure have been investigated. It is found that the combustion temperature increases with increasing preheating temperature and results in melting of the NiTi compound above 450 degrees C. Moreover, the preheating temperature has been shown to have a significant effect on the microstructure of the SHS-synthesized porous Ni-Ti SMAs, and the mechanism of anisotropy in pole structure is attributed to the convective flows of Liquid and argon during combustion. (C) 2000 Acm Metallurgica Inc. Published by Elsevier Science Ltd. Ali rights reserved.
关键词:
self-propagating high-temperature synthesis (SHS);porous Ni-Ti;shape-memory alloys;combustion synthesis
Acta Materialia
Cyclic deformation behavior and surface deformation features of [011] multiple-slip-oriented single crystals were investigated at constant plastic shear strain amplitude (gamma(pl)) in the range of 1.1x10(-4)- 7.2 x 10(-3) at room temperature in air. It was revealed that the cyclic deformation characteristic of [011] copper single crystal is quite different from that of [001] and [(1) over bar 11] multiple-slip-oriented copper single crystals. The [011] crystal exhibits a rather low initial hardening rate, which does not increase notably even under higher plastic strain amplitudes. The cyclic stress-strain (CSS) curve of the [011] crystal exhibit a clear plateau region over the range of plastic strain amplitude investigated. Surface observations indicated that the primary persistent slip bands (PSBs) already occur under a lower strain amplitude of 1.1x10(-4), but the operation of secondary slip was strongly suppressed by the corresponding dislocation interactions even at high strain amplitudes. This slip characteristic was suggested to be associated with the occurrence of the plateau region. When gamma(pl)greater than or equal to 2.5 x 10(-3), two types of deformation bands (DBI and DBII) formed on the specimen surface and their habit planes are perpendicular to each other strictly. An analysis based on the classical crystallographic deformation geometry was proposed to interpret the existence of an irreversible rotation of crystal in single crystal subjected to symmetrical push-pull loading. This phenomenon is assumed to be an essential reason for the formation of DBI and DBII. When gamma(pl)greater than or equal to 5.0 x 10(-3) another type of deformation band (DBIII) was observed on the specimen surface and its habit plane is exactly (001) with the maximum shear stress acting on it. The favorable macroscopic state of stress may be responsible for the formation of DBIII, giving rise to the cyclic softening in the cyclically deformed [011] copper single crystals at high strain amplitudes (y(pl) greater than or equal to 5.0 x 10(-3)). (C) 1998 Acta Metallurgica Inc. Published by Elsevier Science Ltd. Ali rights reserved.
关键词:
dislocation-structures;fatigue damage;behavior;amplitude;localization
