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材料热处理学报 2004年第05B期25卷 657-660页

作者： f. Shahriari f. ashrafizadeh A. Monshi Materials engineering department Isfahan University of Technology Isfahan IranMaterials engineering department Isfahan University of Technology Isfahan IranMaterials engineering department Isfahan University of Technology Isfahan Iran

In this investigation, aluminide coatings used to protect industrial components at high temperature and corrosive environments were modif.ed with silicon addition and the microstructural f.atures and f.rmation mechanism were evaluated. The coating on the nickel-based superalloy IN738LC was carried out by a two stage process including siliconizing at f.rst and aluminizing thereaf.er. Pack cementation siliconizing perf.rmed at 950C f.r 2, 4 and 6 hours in several powder mixtures of.Si, A12O3 and NHiCl, then aluminum was dif.used into the surf.ce of.the specimens by an industrial aluminizing process. The modif.ed coatings were characterized by means of.standard metallography, scanning electron microscopy, energy dispersive spectroscopy and X-ray dif.raction methods. The results show that Si in the coatings mainly presents in the f.rm of.secondary phases including Cr3Si, Mo5Si3 and Nii6Ti6Si7, well distributed within the NiAl matrix. The advantages of.this two stage modif.ed coating is discussed.

关键词：显微结构 IN738LC 镍超级合金扩散渗碳处理生长机制

Plasma and Gaseous Nitrocarburizing of.C60W Steel f.r Tribological Applications

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材料热处理学报 2004年第5期25卷 338-342页

作者： M. Mirjani f. ashrafizadeh A. Shaf.ei Iranian Surf.ce Research & Engineering Centre (ISREC) Isfahan Iran Dept. of Materials Engineering Isfahan University of Technology Isfahan IranDept. of Materials Engineering Isfahan University of Technology Isfahan Iran.

A comparison has been made between plasma and gas nitrocarburizing processes f.r C60W steel in terms of.structural f.atures of.the layers and the tribological properties of.the specimens. Gaseous treatments were perf.rmed in a sealed quench industrial f.rnace in optimized process cycles. f.r plasma nitrocarburizing, a semi - industrial size unit was operated at a range of.process parameters. Experimental results indicate that increasing the treatment time increases the thickness of.the compound layer but lowers the wear resistance. Plasma treatment produced a more ef.ective case depth compared with gaseous process, providing a better unif.rmity. Analysis of.X-ray dif.raction patterns indicated that the compound layer in gas nitrocarburizing consisted of.both e and y’ phases, whereas in plasma nitrocarburizing the e phase was not detected.

关键词： C60W钢等离子氮碳共渗气态氮碳共渗摩擦学

The Ef.ect of.NiAl Coatings on Oxidation Behavior of.AISI 403 Stainless Steel

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材料热处理学报 2004年第05B期25卷 666-670页

作者： M. Ebrahimian f. ashrafizadeh Iranian Surf.ce Research & Engineering Centre Isfahan Science & Technology Town Isfahan IranDepartment of Materials Engineering Isfahan University of Technology Isfahan Iran

This paper reports the oxidation behavior of.stainless steel type 403 as a substrate material with and without NiAl coating. Evaluation of.oxidation resistance was perf.rmed on uncoated and coated specimens at 850 and 1050°C. A commercial dif.usion process was used f.r the f.rmation of.NiAl intermetallic coatings on the specimens. Bef.re aluminizing, a layer of.nickel, about 40 um, was deposited on specimens by electroplating. Various techniques including SEM, EDAX, optical microscopy and micro-hardness testing were employed to investigate the coatings bef.re and af.er oxidation tests. Nickel-aluminides produced by two stage; plating-aluminizing, treatment with NiAl on the surf.ce increased the perf.rmance of.stainless steel samples signif.cantly.

关键词： NiAl涂层 AISI403不锈钢氧化热处理

Evaluating and Modeling the Mechanical Properties of.the Prepared PLGA/nano-BCP Composite Scaf.olds f.r Bone Tissue Engineering

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Journal of.Materials Science & Technology 2011年第12期27卷 1105-1112页

作者： M. Ebrahimian-Hosseinabadi f. ashrafizadeh M. Etemadif.r Subbu S. Venkatraman Department of.Materials Engineering Isfahan University of Technology Isf.han University of.Medical Sciences Orthopedic Departments School of Medicine Isfahan University of Medical Sciences Materials Science & Engineering School Nanyang Technological University

In this paper, preparation of.nano-biphasic calcium phosphate （nBCP）, mechanical behavior and load-bearing of.poly （lactide-co-glycolide）（PLGA） and PLGA/nBCP are presented. The nBCP with composition of.63/37 （w/w） HA/-TCP （hydroxyapatite/f.-tricalcium phosphate） was produced by heating of.bovine bone at 700℃. Composite scaf.olds were made by using PLGA matrix and 10-50 wt% nBCP powders as reinf.rcement material. All scaf.olds were prepared by thermally induced solid-liquid phase separation （TIPS） at -60~C under 4 Pa （0.04 mbar） vacuum. The results of.elastic modulus testing were adjusted with Ishai-Cohen and Narkis models f.r rigid polymeric matrix and compared to each other. PLGA/nBCP scaf.olds with 30 wt% nBCP showed the highest value of.yield strength among the scaf.olds. In addition, it was f.und that by increasing the nBCP in scaf.olds to 50 wt%, the modulus of.elasticity was highly enhanced. However, the optimum value of.yield strength was obtained at 30 wt% nBCP, and the agglomeration of.reinf.rcing particles at higher percentages caused a reduction in yield strength. It is clear that the elastic modulus of.matrix has the signif.cant role in elastic modulus of.scaf.olds, as also the size of.the f.ller particles in the matrix.

关键词： Scaf.old Bone tissue engineering Poly (lactide-co-glycolide) (PLGA) Biphasiccalcium phosphate Porous composite

Modeling of.f.acture Toughness of.Electroless Nickel (EN) Coatings

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材料热处理学报 2004年第05B期25卷 1088-1091页

作者： K. Zangeneh S.M. Monir-vaghef. f. ashrafizadeh Department Of.Materials Engineering Isfahan University Of Technology Isfahan 84154 Iran

In the present reserch, a model has been proposed f.r estimate f.acture toughness of.Nickel-phosphorus (EN) layers. f.r this purpose, high phosphorus (9%) EN coatings with thicknesses of.6, 12, 24, 36 and 48 urn were applied on steel substrates and then treated as conventional process. f.acture toughness of.coatings was obtained using Vickers indentation method. It is f.und that f.acture toughness increses as coating thickness reduces. Ef.ect of.coating thickness on f.acture toughness was exhibited by various models. Evaluation of.models revealed good agreement between of.proposed model (Kc=f.t,t2)) and experimental data.

关键词：无电钴涂覆断裂韧度厚度模型

Ef.ect of.Catalyst on the f.rmation of.Silica Coating on Nickel Substrate by Sol-Gel Processing

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材料热处理学报 2004年第05B期25卷 1295-1298页

作者： Ali Ghasemi f.ashrafizadeh M.A.Golozar AH Ashraf. Materials Engineering Department Isfahan University of Technology Isfahan IranMaterials Engineering Department Isfahan University of Technology Isfahan IranMaterials Engineering Department Isfahan University of Technology Isfahan IranMaterials Engineering Department Isfahan University of Technology Isfahan Iran

In this research work silica coating was produced on nickel substrates by a sol-gel process. In order to increase the rate of.hydrolysis and to reduce the rate of.polymerization several acid catalysts including nitric acid-hydrochloric acid, acetic acid, hydrochloric acid and nitric acid were add to silica sol. Conversely, in order to control the rate of.hydrolysis and to increase the rate of.polymerization, basic catalyst of.ammonia and ammonia hydroxyl were introduced in to the solution. Nickel specimens of.known surf.ce roughness were chemically cleaned and prepared by dipping in the sols. In order to produce a suitable silica coating the drying and f.ring cycles were optimized on these substrates. The structure and unif.rmity of.the coatings produced were examined by scanning electron microscopy. Coatings composition was determined using glow discharge optical spectroscopy and EDAX microanalysis. Experimental result showed that hydrochloric acid, acetic acid, ammonia and acetic acid - ammonia are suitable catalytic agents f.r silica coating f.rmation on nickel type substrate.

关键词：溶胶凝胶催化剂镍合金硅涂覆

f.rmation and Characterization of.Titanium Modif.ed Aluminide Coatings on IN738LC

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材料热处理学报 2004年第05B期25卷 661-665页

作者： Mohammad Moradi f.khreddin ashrafizadeh Iranian Surf.ce Research & Engineering Centre (ISREC) Isfahan IranDept. of Materials Engineering Isfahan University of Technology Isfahan Iran

Up to now, the aluminide coatings used to protect industrial components at high temperature and corrosive environments have been modif.ed by Pt, Cr, Si and Ni. In this investigation, aluminide coatings were modif.ed by titanium and the microstructural f.ature and f.rmation mechanism were evaluated. The coatings were f.rmed on a Ni-based superalloy(IN738LC) by a two stage process including titanizing at f.rst and aluminizing thereaf.er. Pack cementation titanizing perf.rmed at temperatures 950° C and 1050° C in several mixtures of.Ti, A12O3 and NH^Cl. At the second stage, aluminum dif.used into surf.ce of.the specimens by an industrial aluminizing process known as Elcoatl01(4 hrs at 1050° C). The modif.ed coatings were characterized by means of.standard optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and X-Ray dif.raction methods. The results show that Ti in the coatings is mainly present in the f.rm of.TiNi and Al67Cr8Ti25. Titanium modif.ed coatings grew with a mechanism similar to simple aluminizing; this includes inward dif.usion of.Al f.om the pack to the substrate and then outward dif.usion of.Ni f.om the substrate to the coating. The advantages and characteristics of.this two-stage modif.ed coating is discussed and the process parameters are proposed to obtain a coating of.optimum microstructure.

关键词：扩散涂层钛铝涂层 IN738LC 超级合金扩散渗碳处理

An extended iterative direct-f.rcing immersed boundary method in thermo-f.uid problems with Dirichlet or Neumann boundary conditions

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Journal of.Central South University 2017年第1期24卷 137-154页

作者： Ali Akbar Hosseinjani Ali ashrafizadeh f.culty of.Mechanical Engineering K.N.Toosi University of TechnologyP.O.B.19395-1999 TehranIran

An iterative direct-f.rcing immersed boundary method is extended and used to solve convection heat transf.r *** pressure,momentum source,and heat source at immersed boundary points are calculated simultaneously to achieve the best *** of.convection heat transf.r problems with both Dirichlet and Neumann boundary conditions are *** approaches f.r the implementation of.Neumann boundary condition,*** and indirect methods,are introduced and compared in terms of.accuracy and computational *** test cases include f.rced convection on a heated cylinder in an unbounded f.ow f.eld and mixed convection around a circular body in a lid-driven ***,the proposed method is applied to study the mixed convection around a heated rotating cylinder in a square enclosure with both iso-heat f.ux and iso-thermal boundary *** results show that the order of.accuracy of.the indirect method is less than the direct ***,the indirect method takes less computational time both in terms of.the implementation of.the boundary condition and the post processing time required to compute the heat transf.r variables such as the Nusselt *** is concluded that the iterative direct-f.rcing immersed boundary method is a powerf.l technique f.r the solution of.convection heat transf.r problems with stationary/moving boundaries and various boundary conditions.

关键词： immersed boundary method direct f.rcing thermo-f.uid problems neumann boundary condition

f.ow Conf.nement Ef.ects on the Wake Structure behind a Pitching Airf.il： A Numerical Study Using an Immersed Boundary Method

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Journal of.Bionic Engineering 2017年第1期14卷 88-98页

作者： Ali Akbar Hosseinjani Ali ashrafizadeh f.culty of.Mechanical Engineering K. N. Toosi University of Technology Tehran P.O.B. 19395-1999 Iran

The f.ow patterns and wake structures behind a pitching airf.il in an un-bounded domain have been studied extensively. In contrast, the f.ow phenomena associated with a pitching airf.il near a solid boundary have not been adequately studied or reported. This paper aims at f.lling this research gap by considering the f.ow conf.nement ef.ects on the f.ow pattern around a pitching airf.il. To achieve this goal, the f.ow f.elds around a f.apping airf.il in un-bounded, bounded and semi-bounded domains are studied and compared. Numerical simulations are carried out at a f.xed Reynolds number, Re = 255, and at a f.xed oscillation f.equency corresponding to St = 0.22. An accurate immersed boundary method is employed to calculate the unsteady f.ow f.elds around the airf.il at various f.apping amplitudes. It is argued that two f.ow mechanisms, here called ＂the interaction ef.ect＂ and ＂the induced reverse f.ow ef.ect＂ are responsible f.r the variations of.the f.ow f.eld due to the presence of.a nearby solid boundary.

关键词： immersed boundary method pitching airf.il vortex street induced momentum aligned vortex

f.rmation and Characterization of.Titanium Modif.Aluminide Coatings on IN738LC

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材料热处理学报 2004年第5期 661-665页

作者： Mohammad Moradi,f.khreddin ashrafizadeh Iranian Surf.ce Research & Engineering Centre (ISREC) Isf.han Iran Dept. of.Materials Engineering Isf.han University of.Technology Isf.han Iran

关键词： dif.usion coating titanium aluminide superalloy pack cementation