Papers by Keyword: Intermetallic Compounds

Abstract: Fast electron irradiation can induce the solid-state amorphization (SSA) of many intermetallic compounds. The occurrence of SSA stimulated by fast electron irradiation was found in the Al_0.5TiZrPdCuNi high-entropy alloy (HEA). The relationship between the occurrence of SSA in intermetallic compounds under fast electron irradiation and the empirical alloy parameters for predicting the solid-solution-formation tendency in HEAs was discussed. The occurrence of SSA in intermetallic compounds was hardly predicted, only by the alloy parameters of δ or ΔH_mix, which have been widely used for predicting solid-solution formation in HEAs. All intermetallic compounds with ΔH_mix ≤ -35 kJ/mol and those with δ ≥ 12.5 exhibit the occurrence of SSA. This implies that the intermetallic compounds with a largely negative ΔH_mix value and a largely positive δ parameter are favorable for the occurrence of SSA.

Abstract: The first-principles calculations by CASTEP program based on the density functional theory is applied to calculate the cohesive energy, enthalpy of formation, elastic constant, density of states and Mulliken population of Ag₃Sn、AgZn₃ and Ag₅Zn₈. Furthermore, the elastic properties, bonding characteristics, and intrinsic connections of different phases are investigated. The results show that Ag₃Sn、AgZn₃ and Ag₅Zn₈ have stability structural, plasticity characteristics and different degrees of elastic anisotropy; Ag₃Sn is the most stable structural, has the strongest alloying ability and the best plasticity. AgZn₃ is the most unstable structure, has the worst plasticity; The strength of Ag₅Zn₈ is strongest, AgZn₃ has the weakest strength, the largest shear resistance, and the highest hardness. Ag₅Zn₈ has the maximum Anisotropy index and Ag₃Sn has the minimum Anisotropy index. Ag₃Sn、AgZn₃ and Ag₅Zn₈ are all have covalent bonds and ionic bonds, the ionic bonds decrease in the order Ag₃Sn>Ag₅Zn₈>AgZn₃ and covalent bonds decreases in the order Ag₅Zn₈>Ag₃Sn>AgZn₃.

Abstract: Magnetic force microscopy (MFM) and magnetometry, scanning electron microscopy (SEM) and atomic force microscopy (AFM) are used to study the magnetic and structural properties of the (Nd,Pr)-Fe–B and (Nd,Ho)-(Fe,Co)-B alloys. The alloys are synthesized using an arc or induction furnaces. The nanocrystalline state of the (Nd,Ho)-(Fe,Co)-B alloys is reached by two techniques, namely, melt spinning (MS) and severe plastic deformation (SPD). Hydrogenation and multistage treatment of (Nd,Ho)-(Fe,Co)-B alloys, which includes severe plastic deformation of melt-quenched ribbons and subsequent heat treatment, is also used. The surface morphology and domain structure of samples are studied. These pictures are used to interpret the observed magnetic hysteresis loops of the samples. It was found that multistage treatment allows one to obtain samples with higher values of coercivity due to the formation of a special microstructure with oval grain (the aspect ratio equal to ∼ 3).

Abstract: In the metal inert gas (MIG) weld-brazing process, the lap-joint welds between 5052 aluminum alloy and automotive galvanized steel sheet were achieved employing an automatic MIG welding machine. The different percentage of helium (He) gas addition to pure argon (Ar) shielding gas was selected to investigate the performance of lap-joint welds such as appearance of weld bead surface, weld bead geometry, microstructure, tensile strength, fracture surface of welds and thickness of intermetallic compounds (IMCs) layer between the dissimilar materials in the brazing zone. The results showed that the lap-joint welds produced by adding 5% and 10% He gas to Ar shielding gas were provided with better performance of specimens. The average tensile strength of lap-joint welds between 5052 aluminum alloy and automotive galvanized steel sheet is 206.23 MPa. In additions, the amount of porosity in the fusion zone that specimens produced by using 10% He addition to Ar-based shielding gas is less than others. It can be found that the thickness of IMCs layer between the weld bead and automotive galvanized steel sheet from 3.30 μm to 4.90 μm.

Abstract: Innovative technology of HDTV-borating, that is distinguished by high hardness, strength, wear resistance and corrosion resistance occupies a special place among the hardening processes for steels and construction materials. During the new technology process HDTV-boration of structural steel 65Mn (65Г in Russian) under a mix layer of charge mixture based on fused borate fluxing agent P-0.66, boron carbide and intermetallic compounds Fe_xAl_y, Ni_xAl_y. Using the methods of X-ray phase analysis, spectrography and metallography, the composition and structure of coatings were determined, the microhardness distribution over the coating thickness was studied. In the coatings, new phases of intermetallic compounds, the double superhard boride Fe₂AlB₂, were found; in the coatings, the base iron boride is FeB, what leads to an increase in their hardness and wear resistance. Modification of boride coatings formed by intermetallic compounds with melting temperatures close to the process temperature of HFC surfacing leads to a decrease in the cracks number and the appearance of new consumer qualities of the material.

Abstract: The paper presents a new technological scheme for obtaining bimetallic materials of the composition "aluminum casting alloy - sintered iron powder" by the method of joint stamping. The results of experimental studies of the effect of process conditions on the physicomechanical properties of the starting materials and the adhesive strength of the final bimetal blank are presented.

Abstract: An experimental study of the phase composition for nine samples of the Cu–Ni–Ce–La alloys with different content of components was carried out. The nickel concentration in the experimental samples varies from 3 to 40 wt. %, the sum of cerium and lanthanum concentrations was not exceed 7 wt. %. Alloys samples of the system Cu–Ni–Ce–La were studied using scanning electron microscopy and microprobe analysis, as well as X-ray analysis. Also, Vickers micro hardness was measured on the cross sections of the experimental samples. In this work, the conditions of intermetallic compounds formation in the as-cast samples were studied. The results of the work can be used for the technological processes analysis of copper and copper-based alloys production.

Abstract: The effect of processing conditions on microstructure and mechanical properties of Fe-Al-Si powders was studied by means of scanning electron microscopy, X-ray diffraction and nanoindentation. Fe-Al-Si alloy powder was prepared from pure elemental powders by mechanical alloying. Microstructure and mechanical properties of powders were characterized after various durations of mechanical alloying. Special sample preparation technique was developed allowing to characterize the properties of individual powder particles after each step of processing in a planetary ball mill. This step-by-step characterization allowed to find the optimum conditions for subsequent spark plasma sintering.

Abstract: Titanium/steel clad material with excellent mechanical properties and corrosion resistance has important application in the oil, gas and ocean equipment. Due to the metallurgical incompatibility of titanium and steel, the mechanical properties of weld joint would completely lose when the brittle intermetallic phase existed in the fusion welding process. Therefore, the gas tungsten arced welding (TIG) + metal inert-gas welding (MIG) + metal active-gas welding (MAG) with pure vanadium and pure copper composite filler metals for welding connection experiment in this study was carried out on Ø610mm×(14+2)mm TA1/X65 titanium/steel clad pipe fitting (titanium cladding with thickness 2 mm, X65 pipeline steel with thickness 14 mm). The microstructure, interface element distribution, main phase, microhardness distribution on cross section and mechanical properties of butt welds were researched by using OM, XRD, EDS element mapping, microhardness and tensile tests. The result showed that the use of pure vanadium and pure copper composite filler metals for welding connection could effectively avoid the production of intermetallic compounds in the process of titanium/steel composite pipe fusion welding. The deposited metal of titanium, vanadium, copper and steel had obvious zoning, the inter-diffusion melting phenomenon was not severe, which is by using solid solution phases to transit zonings of deposited metal. The microstructure of titanium and vanadium transition interface were composed of titanium-based solid solution, the microstructure of vanadium and copper transition interface was composed of vanadium-based solid solution, and the microstructure of copper and steel transition interface were composed of copper-based solid solution. The transition interface had no porosity, crack and other defects. The tensile strength of the weld was 546MPa, which is mainly contributed by the carbon steel layer. With pure vanadium and pure copper as transition filler metal for the welding connection TA1/X65 clad pipe was successfully realized by TIG+MIG+MAG welding method, and the strength index reached the desired effect.

Abstract: In this research, we investigated the influence of indium and antimony additions on the microstructure, mechanical and thermal properties of Sn-3.0Ag-0.5Cu lead free solder alloys. The results revealed that the addition of 0.5 wt.%InSb into SAC305 solder alloys resulted to a reduced melting temperature by 3.8 °C and IMCs phases formed new Ag₃(Sn,In) and SnSb in the Sn-rich matrix with a decreased grain size of 28%. These phases improved the mechanical properties of solder alloys. In addition, the mechanical properties of SAC305 solder alloys increased by adding 0.5 wt.%InSb, resulting in an increase of ultimate tensile strength of 24%, but the percent elongation decreased to 45.8%. Furthermore, the Vickers microhardness slightly increased of the SAC305 solder alloys.