离子钨钼共渗的表观过程

研究了双层辉光离子钨钼相渗在离子轰击条件下形成渗层和无离子轰击时形成沉积层的表观过程。结果表明,在形成沉积层时,由于离子轰击作用已在不存在,使渗层厚度减少２６％,用朗缪尔探针对双层辉光离子钨钼共渗过程进行了等离子体的诊断,等离子体对表现成分有较大影响。合理的等离子体密度范围为５＊１０＾－１１－３＊１０＾１２。     

Surface alloying of magnesium and AZ91 by thermochemical treatment in a medium containing zinc chloride and potassium chloride

Surface layers enriched with zinc were formed on pure magnesium and AZ91 alloy by heating the specimens in contact with paste containing zinc chloride and potassium chloride at 440 °C for 2 h, using no protective atmosphere. The study involved determining the microstructure, phase composition and microhardness of the resulting layers. During the layer formation process, a transient liquid phase occurred at the substrate/paste interface. The layers fabricated on both substrates were about 200 μm in thickness and they were metallurgically bonded to the substrate material. The same process conditions were used for both types of substrates. From the experimental data it is clear that the layer fabricated on magnesium differed in microstructure from that formed on AZ91. The alloyed layer on magnesium was characterised by dendrites of a solid solution of zinc in magnesium surrounded by a lamellar eutectoid structure composed of an MgZn intermetallic phase and a solid solution of zinc in magnesium. In the layer formed on AZ91, aluminium was detected in all the structural constituents. The layer was composed of a solid solution of zinc and aluminium in magnesium and Mg₁₇(Al, Zn)₁₂ and Mg₅Al₂Zn₂ intermetallic phases. The alloyed layers had much higher hardness than the substrate materials.     

用铸渗工艺对消失模铸件件进行表面合金化的研究

利用干砂消失模铸造工艺,对铸铁件表面合金化铸渗机理进行了研究,通过建立数学模型,对铸渗过程中铁水传输进行了理论分析,给出了铸渗量与浇口的大气压力、铁水静压力、渣液阻力及附加压力的关系,提出了铸渗量大小主要取决于铸渗孔道半径的新观点,用正交试验对合金涂层中合金粉粒度,合金粉加入量、溶剂加入量及涂层中聚苯乙烯泡沫加入量等进行了考证,得出最佳工艺配方为：合金粉粒度75－100目,泡沫加入量30％－50％（ψ（B））;溶剂加入量4％,在配制涂料时,适当加入一定量泡沫珠粒,有利于母液透,这与理论推导结果相符,易获得3mm以上合金层厚度,合金层具有珠江体基体及大量M7C3碳化物,并且有高硬度及高抗磨性。     

用铸渗工艺对消失模铸铁件进行表面合金化的研究

利用干砂消失模铸造工艺,对铸铁件表面合金化铸渗机理进行了研究,通过建立数学模型,对铸渗过程中铁水传输进行了理论分析,给出了铸渗量与浇口的大气压力、铁水静压力、渣液阻力及附加压力的关系式,提出了铸渗量大小主要取决于铸渗孔道半径的新观点.用正交试验对合金涂层中合金粉粒度、合金粉加入量、溶剂加入量及涂层中聚苯乙烯泡沫加入量等进行了考证,得出最佳工艺配方为:合金粉粒度75～100目;泡沫加入量30%～50%(ψ(B));溶剂加入量4%.在配制合金涂料时,适当加入一定量泡沫珠粒,有利于母液渗透,这与理论推导结果相符,易获得3 mm以上合金层厚度.合金层具有珠光体基体及大量M7C3碳化物,并具有高硬度及高抗磨性.     

Ni-based superalloy surface alloying by double-glow plasma surface alloying technique

The double-glow surface alloying technique, also called the Xu-Tec/Xu-Loy process, is a novel technique in the field of surface alloying. This technique allows alloy layers with unique physical, chemical and mechanical properties, such as nickel-based alloy layers, stainless-steel layers and age-hardened surface high-speed steel layers to be formed at the surface of treated metallic materials. In this paper, recent research of the application of the double-glow plasma surface alloying technique in the formation of corrosion resistance alloy layers is briefly reviewed. The results of a study of Ni-Cr-Mo-Nb and Ni-Cr-Mo-Cu corrosion-resistant alloying layers as well as composite alloying layers with an electric brush plating Ni interlayer are reported.     

Surface alloying of steels in the process of mechanical pulse treatment

It is shown that intense saturation of the surface layers of a hardened metal with nickel, copper, and chromium from electroplates occurs in the course of mechanical pulse treatment in the zone of frictional contact. In this case, the mass transfer coefficients range from 0.95·10⁻⁷ to 1.1·10⁻⁷ m²/sec. It is established that the number of alloying elements is defined by the number of generated dislocations. Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 34, No. 3, pp. 108–110, May–June, 1998.     

Surface alloying by pulsed intense electron beams

Results of numerical calculations and experimental studies of the thickness of modified layers, distribution of implanted materials, microstructure and phase composition inside the layers following pulsed electron beam treatment are presented. Possible physical mechanisms of the alloying process are discussed. The improvements of surface properties, especially corrosion resistance against liquid lead, are presented. It is shown that corrosion of OPTIFER IVc steel by liquid lead containing 8×10⁻⁶ at% oxygen is avoided by alloying Al into the surface.     

Synthesis of nanocrystalline NiAl over a wide composition range by mechanical alloying

The paper reports the synthesis of nanocrystalline NiAl by mechanical alloying of pure metal mixture and a mixture of prealloyed powder with Ni/Al. A large number of compositions have been studied to establish the phase field of NiAl in the milled state. The phase field of NiAl in the ball milled condition was found to be much wider (10–68 at.% Ni) than its equilibrium phase field (45–59 at.% Ni). The metastable equilibrium achieved by mechanical alloying was identical for a given composition irrespective of the starting ingredients. The crystallite size of NiAl reached a minimum (5 nm) at the phase boundary of NiAl/Ni₃Al.     

Basal-plane stacking-fault energies of Mg alloys: A first-principles study of metallic alloying effects

Generalized stacking-fault energies (GSFEs) of basal-plane stacking faults I₁ and I₂ in Mg alloys have been studied based on first-principles calculations, where 43 alloying elements were considered. It is found that the most contributing features of alloying elements to GSFEs are bulk modulus, equilibrium volume, binding energy, atomic radius and ionization energy. Both bulk modulus and ionization energy exhibit positive relationships with GSFEs, and the others show opposite relationships. Multiple regressions have been performed to offer a quantitative prediction for basal-plane GSFEs in Mg-X systems. GSFEs, alloying effects of elements and the prediction model established within this work may provide guidelines for new Mg alloys design with better ductility.     

Influence of alloying and secondary annealing on anneal hardening effect at sintered copper alloys

This paper reports results of investigation carried out on sintered copper alloys (Cu, 8 at%; Zn, Ni, Al and Cu-Au with 4 at%Au). The alloys were subjected to cold rolling (30, 50 and 70%) and annealed isochronally up to recrystallization temperature. Changes in hardness and electrical conductivity were followed in order to investigate the anneal hardening effect. This effect was observed after secondary annealing also. Au and Al have been found to be more effective in inducing anneal hardening effect.     

Multi-attribute decision-making of cryogenically cooled micro-EDM drilling process parameters using TOPSIS method

The geometrical characteristics of the micro-holes along with the performance measures are matter of critical concern in micro-electrical discharge machining (μEDM) process. This paper presents the multi-attribute decision-making of cryogenically cooled micro-EDM (CμEDM) drilling process. Current (I_p), pulse on duration (T_on), pulse off duration (T_off), and gap voltage (V_g) were the input process parameters preferred to optimize the multiple responses of geometrical characterization including taper angle (TA), overcut (OC), circularity at the entry and exit (C_ent and C_exit), and performance measures including material removal rate (MRR), tool wear rate (TWR), and average roughness (R_a). The Taguchi-based L₂₇ orthogonal array (OA) is used to carry out the experimental runs, and technique for order of preference by similarity ideal solution (TOPSIS) approach is used for the identification of optimal parameters on AISI 304 stainless steel. The optimized result achieved from this approach suggests improved TA, OC, C_ent, C_exit, MRR, and lower TWR, surface roughness (SR) with the combinations of CμEDM drilling process such as I_p of 15 A, T_on of 10?µs, T_off of 30?µs, and V_g of 30?V. Analysis of variance (ANOVA) was conducted to identify the major influencing parameter.     

Surface modification of an aluminium 2124 composite by eutectic alloying

The incorporation of a hard particular dispersion in a metal matrix results in a composite material with unique mechanical and tribological properties. However, once the composite has been fabricated the particular dispersion cannot be rearranged or modified. In this study, the surface of a 2124 aluminium metal matrix composite is modified by eutectic alloying with copper. The results show that by heat treating the composite at a temperature above the eutectic temperature for the Al-Cu system, the distribution of SiC particles can be altered. There is a significant movement of particles towards the surface of the composite and abrasive wear tests show better wear resistance than the unmodified surfaces. This change in wear behaviour is attributed to the absence of severe plastic deformation due to the increase in concentration of hard SiC particles within the surface.     

Effect of existing form of alloying elements on the microhardness of Al-Si-Cu-Ni-Mg piston alloy

Effect of alloying elements including Si, Cu, Ni and Mg with different existing forms on the microhardness of Al-12Si-4Cu-2Ni-2.6Mg (in wt.%) piston alloy was investigated. It is found that microhardness of the alloy reaches to 1.88 GPa when all the Cu, Ni, Mg and 3.63 wt.% Si dissolved in the α-Al matrix, and increases to 2.02 GPa while only the solid-solved Si precipitates to form nanoparticles. The precipitated Si has greater contribution to the alloy's microhardness than the solid-solved Si in the same level. Furthermore, the precipitation of intermetallics containing Cu, Ni and Mg that disperses in the Al-matrix can further improve the microhardness to 2.09 GPa. The hardening efficiency of the intermetallics precipitation of Cu, Mg and Ni on microhardness is less than that of the nanoscale Si precipitates under the same mass fraction. For Cu, Mg and Ni alloying elements, whether dissolving in α-Al matrix or precipitating as nanoparticles, there is no evident difference on improving microhardness of the tested alloy.     

A novel application of micro-EDM process for the generation of nickel nanoparticles with different shapes

This article explains production of nickel nanoparticles through a micro-electrical discharge machining (EDM) process with a combination of different process parameters. The production of nickel nanoparticles was carried out in a dielectric medium (deionized water) with developed micro-EDM while polyvinyl alcohol worked as the stabilizing agent. The characterization of nickel nanoparticle was done by scanning electron microscope (SEM), Energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), UV–Vis spectroscopy, and Fourier transform infrared (FTIR) analysis. From this investigation, the mean crystal size of the nickel nanoparticles was found to be in the range of 15–20?mm for a pulse-on time variation of 2–0.3?µs and the crystal size was found to decrease with the decrease of pulse-on time. It was also observed that with this decrease, the shape and size of nickel nanoparticles change from spherical to needle-like. The dispersion stability of nickel nanofluid was determined by viscosity measurements and the dynamic viscosity was noted to decrease by decreasing the pulse duration. From the FTIR spectrum results, it was confirmed that the synthesized nickel nanoparticles in deionized water were pure and monolithic. UV–Vis–NIR spectroscopy depicted that the band gap energy increases with a reduction in the pulse-on time and obtains a higher band gap (5.31?eV) for 0.3?µs pulse-on time.     

Effects of Alloying Elements on Microstructure and Erosion Resistance of Fe—C—Cr Weld Surfacing Layer

Effects of alloying elements on microstructure and erosion resistance of Fe-C-Cr weld surfacing layer have been studied. The experimental results show that increasing C and Cr content favors improving the erosion resistance of the layer, and the excessive C and Cr result in decreasing the erosion resistance at 90 deg. erosion. That Mo, Nb or Ti improves the erosion resistance of Fe-C-Cr weld surfacing layer is mainly attributed to increasing the amount of M7C3 and forming fine NbC or TiC in austenite matrix, but the excessive Mo, Nb or Ti is unfavorable. The addition of Mo, Nb and Ti in proper combination possesses stronger effect on improving the erosion resistance and the erosion resistance (εA) of Fe-C-Cr weld surfacing layer with fine NbC, TiC and M7C3 distributing uniformly in austenite matrix obviously increases to 2.81 at 15 deg. erosion and 2.88 at 90 deg. erosion when the layer composition is 3.05C, 20.58Cr, 1.88Mo, 2.00Nb and 1.05Ti (in wt pct).     

W18Cr4V激光表面合金化的X射线衍射研究

利用X射线衍射技术研究了高速钢W18Cr4V激光表面合金化后合金化层的相组成。精确计算了碳化物和基体α-Fe的晶格常数。并从理论上分析了激光表面合金化过程中碳化物和基体α-Fe的熔覆特性。     

Effects of process parameters on fatigue behavior and surface integrity of tool steel produced by electrical discharge turning

Electrical discharge machining is used in the production of countless parts with complex geometries and micro dimensions, from many elements of industrial molds to parts of motors and pumps. Also, most of these parts are cylindrical and it is always more meaningful to study their rotational fatigue behavior to predict their response during their operation. This study concentrated on the impacts of machining parameters on the surface quality and fatigue behavior of tool steel shaped by electrical discharge turning. The results based on Taguchi methodology have shown that discharge current affects R_a and R_z more, and pulse duration more affects the mean spacing of profile irregularities, S_m. As a result of the heat affected depth in the machined region, which changes in proportional with the processing parameters, the microhardness decreased from the sample surface to the core. The maximum hardness was measured at current of 12 A, pulse duration of 3 μs and pulse interval of 7 μs. According to the fatigue tests, it was found that the fatigue life decreased with the increase in R_z and S_m values. Moreover, high microhardness and thick recast layer reduced the fatigue strength of the samples with relatively smooth surface topography.     

Surface hardness behaviour of Ti-Al-Mo alloys

The microhardness characteristics of various micro-constituents formed in the Ti-Al-Mo alloys have been investigated. Four alloys having compositions, Ti-40Al-2Mo, Ti-42Al-2Mo, Ti-40Al-6Mo and Ti-42Al-6Mo, have been chosen for this purpose. All of these were heat treated at 1300°C and 1400°C for 1 h and water quenched. All the specimens after above heat treatments have displayed load independent Vickers hardness values (VHN) around 300 g of applied load. The average surface hardness characteristic of the alloys is largely found to be dictated by the phases that are present. The microstructural specific VHN values vary between 600 and 750. The indentation behaviour, however, is governed by the morphologies and length scales of microstructures. The most remarkable finding of the present study pertains to the formation of shear bands around the periphery of the indenter for a finer basket weave microstructure in the Ti-40Al-2Mo. The cluster of finely located slip steps was clearly seen. Such a report is lacking in literature in this class of alloys.     

利用JMatPro软件进行合金覆层成分设计及回火工艺制定

利用JMatPro软件对合金覆层进行计算,模拟分析了不同回火状态下合金覆层内部相组成成分的变化情况与碳化物颗粒的析出情况,预测了合金覆层的相关性能;采用微束等离子熔覆加工方法,在H13钢基体上熔覆制备了合金覆层,研究分析了合金覆层回火前后的组织形态、物相组成、元素分布和显微硬度变化.结果表明,对合金覆层进行200℃回火...     

机械合金化法制备低质量分数Mo-Cu合金

采用机械合金化法制粉、液相烧结和致密化处理工艺,制备了低质量分数的Mo-Cu合金。通过X射线衍射和扫描电镜对Mo-Cu复合粉末形貌、液相烧结和变形加工后合金显微组织进行了分析,研究了各种工艺参数对Mo-Cu合金致密性、拉伸强度和延伸率的影响。结果表明,采用高能球磨机械合金化和液相烧结,可获得相对密度高达98.2%的Mo-Cu合金,再经致密化变形加工处理后,可获得全致密的Mo-Cu合金,在40%变形率的条件下,拉伸强度可达到569MPa,延伸率为6.3%。