Structures and Properties of High-Carbon High Speed Steel by RE-Mg-Ti Compound Modification

The effects of rare earths ( RE )-Mg-Ti compound modification on the structures and properties of high-carbon high speed steel ( HSS ) were researched. The impact toughness (ak), the fracture toughness (Klc)andt hreshold of fatigue crack growth (△Kth)are tested. The thermal fatigue test is done on a self-straining thermal fatigue tester, the wear test is done on a high temperature wear test machine. The results show that the matrix can be reftned by the RE-Mg-Ti compound modification, the euteetic carbides are inclined to spheroidicize and are distributed everdy, the morphology and distribution of eutectic carbides are improved by appropriate RE-Mg-Ti complex modification. After RE-Mg-Ti compound modification, a little effects can be found on the strength, hardness and red hardness, but the fractare toughness(Klc) and threshold of fatigue crack growth (△Kth) are improved in the meantime, the impact toughness (ak) is increased by over one time, and the rasistanee to thermal fatigue and wear resistanee at an elevated temperature are remarkably improved.     

Microstructure and wear behaviour of laser-induced thermite reaction Al<Subscript>2</Subscript>O<Subscript>3</Subscript> ceramic coatings on pure aluminum and AA7075 aluminum alloy

Wear-resistant laser-induced thermite reaction Al2O3 ceramic coatings can be fabricated on pure Al and AA7075 aluminum alloy by laser cladding （one-step method） and laser cladding followed by laser re-melting （two-step method） using mixed powders CuO-Al-SiO2 in order to improve the wear properties of aluminum and aluminum alloy, respectively. The microstructure of the coatings was characterized by scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The wear resistance of the coatings was evaluated under dry sliding wear test condition at room temperature. Owing to the presence of hard α-Al2O3 and γ-Al2O3 phases, the coatings exhibited excellent wear resistance. In addition, the wear resistance of the coatings fabricated by two-step method is superior to that of the coatings fabricated by one-step method.     

A MIXED METHOD OF DETERMINING THETHERMAL STRESS FOR COLD ROLLER

Coldrollerisanimportantcomponentofthemill.Thecoldrolleroftherollingprocessisusedathightemperature,whichwouldcracktherollerandshortentheservicelifeoftheroller.UPtonow,ageneralcalculationmethodofthethermalstressofthecoldrolleristoincreasethesafetycoefficient.Thiscalculationmethodlackstheoreticalanalysis.Inordertosolvethisproblem,thispaperappliesforthefirsttimethenewlydevelopedfiniteanalyticalmethodandtheboundaryfittingcoordinatetransformationmethodtomillpracticeandprovidesaanalyticalbasisoftemp…     

Experimental Study on Young′s Modulus of Concrete

Ｃｏｎｃｒｅｔｅｃｏｍｐｏｎｅｎｔｉｓｗｉｄｅｌｙｕｓｅｄｉｎｉｎｄｕｓｔｒｉａｌａｎｄｃｉｖｉｌｃｏｎｓｔｒｕｃｔｉｏｎｓ .Ｙｏｕｎｇ′ｓｍｏｄｕｌｕｓｉｓａｂｏｕｔｉｔｓｂａｓｉｃｍｅｃｈａｎｉｃｓｃｈａｒａｃｔｅｒｉｓｔｉｃ ,ｗｈｉｃｈｉｓｉｎｄｉｓｐｅｎｓａｂｌｅａｎｄｉｍ ｐｏｒｔａｎｔｆｏｒｓｔｕｄｙｓｕｃｈｐｒｏｂｌｅｍｓａｓｄｅｆｏｒｍａｔｉｏｎ ,ｅｘｐｌｏｓｉｖｅｗａｖｅａｎｄｅａｒｔｈｑｕａｋｅｗａｖｅ .ＴｈｅｒｅｌａｔｉｏｎｂｅｔｗｅｅｎＹｏｕｎｇ′ｓｍｏｄｕｌｕｓａｎｄｔ…     

Flow stress behavior of Cu13Zn alloy deformed at elevated temperature

Ｃｏｎｓｔｉｔｕｔｉｖｅｍｏｄｅｌｉｓａｍａｔｈｅｍａｔｉｃａｌｒｅｐｒｅｓｅｎｔａｔｉｏｎｏｆｔｈｅｄｅｆｏｒｍａｔｉｏｎｒｅｓｐｏｎｓｅｏｆａｍａｔｅｒｉａｌｔｏｅｘｔｅｒｎａｌｌｙａｐ ｐｌｉｅｄｌｏａｄｉｎｇ ,ｉｎｃｌｕｄｉｎｇｅｎｖｉｒｏｎｍｅｎｔａｌｆａｃｔｏｒｓ .Ｔｈｅｐｒｅ ｃｉｓｅｋｎｏｗｌｅｄｇｅｏｆｔｈｅｃｏｎｓｔｉｔｕｔｉｖｅｂｅｈａｖｉｏｒｏｆｔｈｅｍａｔｅｒｉａｌｉｓｔｈｅｆｏｕｎｄａｔｉｏｎｏｆｎｕｍｅｒｉｃａｌｓｉｍｕｌａｔｉｏｎｔｅｃｈｎｏｌｏｇｙｏｆｍａｔｅｒｉ…     

Alteration of diaspore by thermal treatment

Diaspore (α-AlOOH) was heated at various temperatures from 300 to 1000 ℃ for 2 h. The alteration of diaspore by thermal treatment was investigated by differential thermal analysis, thermogravimetric analysis and X-ray diffraction. The mechanism of thermal decomposition of diaspore was discussed according to the Coats-Redfern equation. It is found that after thermal treatment at 500 ℃, diaspore is transformed entirely to corundum (α-Al2O3). Combined with the mass loss ratio obtained from the thermogravimetric analysis data, the activation energies for the thermal treatment of diaspore are calculated as Ea=10.4 kJ/mol below 400 ℃ and Eb=47.5 kJ/mol above 400 ℃, respectively, which is directly related to the structural alteration of diaspore during the thermal treatment. The results indicate that the thermal decomposition of diaspore is conducted primarily by means of an interfacial reaction.     

Synthesis and characterization of Nd doped M-type hexagonal barium ferrite ultrafine powders

Ｂｅｃａｕｓｅｐｅｒｍａｎｅｎｔｂａｒｉｕｍｆｅｒｒｉｔｅｍａｔｅｒｉａｌｐｏｓｓｅｓｓｅｓｒｅｌａｔｉｖｅｌｙｈｉｇｈｓａｔｕｒａｔｉｏｎｍａｇｎｅｔｉｚａｔｉｏｎ ,ｇｒｅａｔｃｏｅｒｃｉｖｅｆｏｒｃｅａｎｄｈｉｇｈｍａｇｎｅｔｉｃａｎｉｓｏｔｒｏｐｙｆｉｅｌｄａｓｗｅｌｌａｓｅｘｃｅｌｌｅｎｔｃｈｅｍｉｃａｌｓｔａｂｉｌｉｔｙａｎｄｃｏｒｒｏｓｉｏｎｒｅｓｉｓｔａｎｃｅ ,ｉｔｈａｓｂｅｅｎｗｉｄｅｌｙｕｓｅｄａｓｔｒａｄｉｔｉｏｎａｌｐｅｒｍａｎｅｎｔｍａｇｎｅｔｓ,ｈｉｇｈ ｄｅｎｓｉｔｙｍ…     

Seismic ultimate bearing capacity of strip footings on slope

The influence of earthquake forces on ultimate bearing capacity of foundations on sloping ground was studied. A solution to seismic ultimate bearing capacity of strip footings on slope was obtained by utilizing pseudo-static analysis method and taking the effect of intermediate principal stress into consideration. Based on limit equilibrium theory, the formulae for computing static bearing capacity factors, Nq, Nc, Nγ, and dynamic bearing capacity factors, Nqd, Ncd, Nγd, which are associated with surcharge, cohesion and self-weight of soils respectively, were presented. A great number of analysis calculations were carried out to obtain the relationship curves of the static and dynamic bearing capacity factors versus various calculation parameters. The curves can serve as the practical engineering design. The calculation results also show that when the values of horizontal and vertical seismic coefficients are 0.2, the dynamic bearing capacity factors Nqd, Ncd and Nγd, in which the effects of intermediate principal stress are taken into consideration, increase by 4%?42%, 3%?27% and 34%?57%, respectively.     

Thermal-mechanical properties of short carbon fiber reinforced geopolymer matrix composites subjected to thermal load

Short carbon fiber preform reinforced geopolymer composites containing different contents of α-Al₂O₃ filler (C_f(α-Al₂O₃)/geopolymer composites) were fabricated, and the effects of heat treatment temperatures up to 1 200 °C on the thermal-mechanical properties were studied. The results show that the thermal shrinkage in the direction perpendicular to the lamination of the composites gradually increases with the increase of the heat treatment temperatures from room temperature (25 °C) to 1 000 °C. However, the composites in the direction parallel to the lamination show an expansion behavior. Beyond 1 000 °C, in the two directions the composites exhibit a larger degree of shrinkage due to the densification and crystallization. The mechanical properties of the composites show the minimum values in the temperature range from 600 to 800 °C as the hydration water of geopolymer matrix is lost. The addition of α-Al₂O₃ particle filler into the composites clearly increases the onset crystalline temperature of leucite (KAlSi₂O₆) from the amorphous geopolymer matrix. In addition, the addition of α-Al₂O₃ particles into the composites can not only help to keep volume stable at high temperatures but also effectively improve the mechanical properties of the composites subjected to thermal load to a certain extent. The main toughening mechanisms of the composites subjected to thermal load are attributed to fiber pulling-out.     

Coating of Fe, Ni on α-alumina microspheres by heterogeneous precipitation

1INTRODUCTION Themagneticmetal coatedceramicoxides,core shellstructuralcompositematerials,inwhichthinmetallicfilmsarecoatedonaceramicoxide matrixwithmicrometerparticlesizes,areattrac tiveduetothecombinationofthefunctionalchar acteristicsofmetalsandmechanicalpropertiesoftheceramicmatrix.Theceramic basedtransition metal coated,core shellcompositessuchasNi coatedAl2O3[1],Fe coatedAl2O3[2],FeNi coated Al2O3[3]orCoFe coatedSiO2[4],havebeenfoundtoexhibitinterestingfunctionalperformancesdue…     

Characteristics and mechanism of abrasive wear for thermoplastic polymers

Abrasive wear characteristics of polyethylene, polystyrene, polymethylmethacrylate, nylon 1010 and polyvinyl chloride were investigated. The volume relative wear resistance coefficients of these thermoplastic polymers are 18%-35% (hardened and low temperature tempered steel 45 was used as a comparing material), and have a linear correlation with square roots of their cohesive energy densities. The coefficients of linear correlation is 0.949. Wear morphologies were observed by scanning electron microscope (SRM). Main wear mechanism of the thermoplastic polymers includes brittle breaking for the hard and brittle polymers & plowing and fatiguing for the soft and tough ones.     

Microscopic characteristics of different fracture modes of brittle rock

Ａｓｕｒｖｅｙｏｆｆｒａｃｔｕｒｅｍｅｃｈａｎｉｃｓｌｉｔｅｒａｔｕｒｅｒｅ ｖｅａｌｓｔｈａｔｒｅｓｅａｒｃｈｗｏｒｋｏｎｒｏｃｋｆｒａｃｔｕｒｅｍｅｃｈａｎ ｉｃｓｈａｓｍａｉｎｌｙｆｏｃｕｓｅｄｏｎＭｏｄｅⅠｆｒａｃｔｕｒｅ (ｏｐｅｎ ｉｎｇｍｏｄｅ) ,ｉｎｐａｒｔｉｃｕｌａｒ,ｏｎＭｏｄｅⅠｆｒａｃｔｕｒｅｔｏｕｇｈｎｅｓｓｔｅｓｔｉｎｇ[1 2 ] .Ｈｏｗｅｖｅｒ,ｐｒｅ ｅｘｉｓｔｉｎｇｃｒａｃｋｓｉｎｒｏｃｋｍａｔｅｒｉａｌｓｏｒｄｉｓｃｏｎｔｉｎｕｉｔｉｅｓｉｎｒｏｃｋｍａｓｓｅｓａｒｅｓｅ…     

Analysis of the effects of the heat of sorption on the process of heat transfer in moisture exchange across a membrane

A theoretical study has been conducted to investigate the effects of mass transfer on heat transfer in moisture exchange across a membrane and a mathematical model describing the heat transfer process with consideration of the heat of sorption was established. A dimensionless variable, Ψ =JLλ /δ (T ₁₀−T ₂₀), which controls the effect of the heat of sorption on the heat transfer in membrane process, was obtained through theoretical analysis, and the effects of Ψ on the heat transfer process were analyzed. Results showed that in the case that the temperature gradient and mass transfer are in the same direction, the effective heat flux changes the direction at Ψ=1. For Ψ<1, the heat transfers from high to low temperature sides through the membrane, and the total thermal resistance increases with increasing the moisture flux across membrane or reducing the temperature difference between the bulk flows on the two sides of membrane. For Ψ>1, the overall effect of the heat and mass transfer is that the effective heat flux points from low to high temperature sides and the total thermal resistance decreases with increasing the mass flux or reducing the temperature difference. In the case that the temperature gradient and mass transfer are in the opposite directions, the existence of the heat of sorption acts to enhance the heat transfer from high to low temperature sides, causing a reduced total thermal resistance, and the greater the mass flux or the smaller the temperature difference, the smaller the total thermal resistance. Supported by the National Natural Science Foundation of China (Grant No. 50576040)     

Thermodynamic assessment of Au-Zr system

1　INTRODUCTIONChemicalvapordeposition (CVD)diamondholdsgreatpromiseinsolvingthermalmanagementprobleminhigh performancemulti chipmodules (MCMs) .However ,thismaterialdoespresentsometechnologi calchallenges ,onebeingthedevelopmentofreliablemetallizationsystems[1] .Thedesirablecharacteristicsofametallizationsystemare goodadhesiontothesubstrate ,lowstress ,goodelectricalconductivityandminimalreactionsatsubsequentprocessingtempera tures (upto 4 0 0℃ ) [2 ] .Goldisusuallychosenasthemetalfor…     

Influence of interfacial strength on the fracture toughness of glass-ceramic matrix composites

Nine kinds of glass-ceramic matrix composites with different compositions and interfacial strength (τ _s) were prepared. The influence of τ _s on the fracture toughness(K _1c) of composites was studied. It was discoved that, for the system no chemical reaction taking place at the interface, K _1c increased proportionally with τ _s increasing at the first stage, then decreased when τ _s reached a certain value. According to this result, a model of relationship between τ _s, thermal mismatch (Δα _r) and K _1c was built up. If a chemical reaction took place and a new phase was formed in the interface, the K _1c of composite was effected by the combination of τ _s, chemical bonding, radial interfacial stress and other factors. Project supported by the National Natural Science Foundation of China Synopsis of the first author Wang Lingsen, professor, born in 1938, current research field: special ceramic and ceramic matrix composite, etc.     

Microstructural features and properties of high-hardness and heat-resistant dispersion strengthened copper by reaction milling

The oxide dispersion strengthened copper alloys are attractive due to their excellent combination of thermal and electrical conductivities,high-temperature strength and microstructure stability.To date,the state-of-art to fabrication of them was the internal oxidation (IO) process.In this paper,alumina dispersion strengthened copper (ADSC) powders of nominal composition of Cu-2.5 vol%Al2O3 were produced by reaction milling (RM) process which was an in-situ gas-solid reaction process.The bulk ADSC alloys for electrical and mechanical properties investigation were obtained by sintering and thereafter hot extrusion.After the hot consolidation processes,the fully densified powder compacts can be obtained.The single γ-Al2O3 phase and profile broaden effects are evident in accordance with the results of X-ray diffraction (XRD);the HRB hardness of the ADSC can be as high as 95;the outcomes should be attributed to the pinning effect of nano γ-Al2O3 on dislocations and grain boundaries in the copper matrix.The electrical conductivity of the ADSC alloy is 55%IACS (International Annealing Copper Standard).The room temperature hardness of the hot consolidated material was approximately maintained after annealing for 1 h at 900 ℃ in hydrogen atmosphere.In terms of the above merits,the RM process to fabricating ADSC alloys is a promising method to improve heat resistance,hardness,electrical conductivity and wear resistance properties etc.     

Synthesis and characterization of arsenate antimonic acid AAAc(1 : 1)

The AAAc(1 : 1) was synthesized in water by As₂O₃ and Sb₂O₃ with molar ratio of 1 : 1. AAAc(1 : 1) was characterized by Raman, IR, TG/DTG, DSC, XPS and XRD. The results show that there are four peaks to v _s of As-OH, As-O-Sb, Sb-OH and Sb-O-Sb in Raman spectra of AAAc(1 : 1) at 100 – 1 000 cm⁻¹. The solution of AAAc(1 : 1) was also titrated with KOH solution. The titration results show that AAAc(1 : 1) is a hexabasic acid with dissociation constants of k ₁=3.62 × 10⁻², k ₂=3.05 × 10⁻³, k ₃=6.43 × 10⁻⁶, k ₄ =9.78 × 10⁻⁸, k ₅=1.32 × 10⁻¹¹, k ₆=3.87 × 10⁻¹². AAAc(1 : 1) has a good solubility and stability in water, its solid obtained by free volatilizing water from its solution under air at ambient temperature is amorphous. Chemical and thermal analysis show that the composition of AAAc(1 : 1) is As₂O₅ · Sb₂O₅ · 8H₂O in air at 25 °C. AAAc(1 : 1) has the structure of AsO(OH)₂-OH-Sb(OH)₄-O-Sb(OH)₄-OH-AsO(OH)₂ or As(OH)₃-O-Sb(OH)₄-O-Sb(OH)₄-O-As(OH)₃ (isomerism) through experimental determination and geometry optimization. Foundation item: Project(50274075) supported by the National Natural Science Foundation of China     

Dynamic recrystallization behavior of 35CrMo structural steel

1　ＩＮＴＲＯＤＵＣＴＩＯＮＤｕｒｉｎｇｈｏｔｗｏｒｋｉｎｇ ,ｓｅｖｅｒａｌｍｅｔａｌｌｕｒｇｉｃａｌｐｈｅｎｏｍｅｎａｓｕｃｈａｓｗｏｒｋ ｈａｒｄｅｎｉｎｇ (ＷＨ ) ,ｄｙｎａｍｉｃｒｅｃｏｖｅｒｙ (ＤＲＶ) ,ａｎｄｄｙｎａｍｉｃｒｅ ｃｒｙｓｔａｌｌｉｚａｉｔｏｎ (ＤＲＸ )ｏｃｃｕｒｓｉｍｕｌｔａｎｅｏｕｓ ｌｙ[1 5 ] .Ｅｓｐｅｃｉａｌｌｙ ,ｔｈｅｏｃｃｕｒｒｅｎｃｅｏｆＤＲＸ ,ｃａｎｒｅｆｉｎｅｇｒａｉｎａｎｄｒｅｄｕｃｅｄｅｆｏｒｍａｔｉｏｎｒｅｓｉｓｔａｎｃｅｉｎｐｒａｃｔｉｃａｌｈｏｔ ｗ…     

THE PROCESS AND MECHANISM OF TiAl－BASED ALLOY SYNTHESIZED FROM Ti AND AlP OWDERS

ＴＨＥＰＲＯＣＥＳＳＡＮＤＭＥＣＨＡＮＩＳＭＯＦＴｉＡｌ－ＢＡＳＥＤＡＬＬＯＹＳＹＮＴＨＥＳＩＺＥＤＦＲＯＭＴｉＡＮＤＡｌＰＯＷＤＥＲＳＸｉｏｎＡｘＸｉａｎｙ；ＨｕａｎｇＢａｉｙｕｎ（ＰｏｗｄｅｒＭｅｔａｌｌｕｒｇｙＲｅｓｅａｒｃｈＩｎｓｔｉｔｕｉｅ...     

Thermoelectric properties of Ca3Co4O9 ceramics

Ca₃Co₄O₉ ceramics were prepared using the sol-gel process with ordinary pressing sintering and their thermoelectric properties were measured from room temperature to 673 K. The experimental results show that single phase Ca₃Co₄O₉ can be fabricated at 750–900 °C in different citrate acid molar proportions for 0.2–1.0. For all the oxides, both the Seebeck coefficients S and the electrical conductivities κ increase with the increasing temperature. The Seebeck coefficients S are all positive. The thermal conductivities k increase with the increasing temperature also and the lattice thermal conductivity κ _l plays an important role to the thermal conductivity κ. The citrate acid molar proportions have a large influence on the particle sizes, which influences the thermoelectric properties of the ceramics. The figure of merit increases with the increasing temperature and reaches 4.5×10⁻⁵ K⁻¹ at 573 K for the sample in the citrate acid molar proportion of 0.46.