A Study of the Effect of Nanosized Particles on Transient Liquid Phase Diffusion Bonding Al6061 Metal–Matrix Composite (MMC) Using Ni/Al2O3 Nanocomposite Interlayer

Transient liquid phase (TLP) diffusion bonding of Al-6061 containing 15 vol pct alumina particles was carried out at 873 K (600 °C) using electrodeposited nanocomposite coatings as the interlayer. Joint formation was attributed to the solid-state diffusion of Ni into the Al-6061 alloy followed by eutectic formation and isothermal solidification of the joint region. An examination of the joint region using an electron probe microanalyzer (EPMA), transmission electron microscopy (TEM), wavelength-dispersive spectroscopy (WDS), and X-ray diffraction (XRD) showed the formation of intermetallic phases such as Al₃Ni, Al₉FeNi, and Ni₃Si within the joint zone. The result indicated that the incorporation of 50 nm Al₂O₃ dispersions into the interlayer can be used to improve the joint significantly.     

Mechanical Properties of a Ni–Cr–Mo Steel Subjected to Room Temperature Carburizing Using Surface Mechano-Chemical Carburizing Treatment (SMCT)

Surface mechano-chemical carburizing treatment (SMCT) is a modified version of surface mechanical attrition treatment and it is one of the cutting-edge technologies for producing hard nano-crystalline surface in metallic materials. In the present study, a case carburized surface layer is achieved in 1.75 Ni–Cr–Mo steel at room temperature using SMCT. Activated charcoal powder is continuously fed during the process so as to achieve the carbon diffusion into the surface layer. The SMCT process has been carried out for different periods say 15, 30, 45 and 60 min respectively. The microstructure and surface chemical composition is investigated by using TEM and XRF analysis. The mechanical properties such as yield strength (YS), ultimate tensile strength (UTS), fracture toughness and surface hardness of SMCT samples have been investigated using universal testing machine, Plain strain fracture toughness test and Microvickers hardness test respectively. The surface carbon content has been found to increase linearly and grain size reduces continuously with processing time. A 60 min SMCT samples reveal 0.8% C and about 10 nm grains over the surface. The SMCT samples show significant improvement in mechanical properties. The surface hardness increases from 180 HV_0.1 to ~ 878 HV_0.1 by 60 min of treatment. About 55% increment in the YS and 30% increment in UTS is achieved by 60 min of SMCT. It is also interesting to note that the fracture toughness of the samples enhances from 24 to 47 MPa \( \sqrt m \) after 60 min of SMCT.     

Development of a Numerical Model for Simulating Transient Liquid Phase (TLP) Bonding Involving Two Solid–Liquid Interfaces that Concurrently Undergo 2D or 3D Migration

A new numerical model is developed for transient liquid phase (TLP) bonding involving two solid–liquid interfaces that concurrently undergo two-dimensional (2D) or three-dimensional (3D) migration in contrast to previous models in the literature where two solid–liquid interfaces are assumed to undergo one-dimensional (1D) migration. The developed model which incorporates variable diffusivity and conserves solute by using a unique hybrid explicit–fully implicit approach and an adaptable space discretization based on Murray–Landis transformation, respectively, is used to investigate the kinetics of the process and major predictions of the model are experimentally validated. It is found that in contrast to the case of 1D migration, despite matching material and bonding conditions, there is a transition from conventional symmetric solidification behavior to asymmetric solidification behavior such that the extent of isothermal solidification is consistently larger on the substrate in which curvature reduces along the direction of solute diffusion. Moreover, aside from what is generally known that the kinetics of isothermal solidification is controlled by diffusivity, equilibrium concentrations at the interface and initial substrate composition, this work shows that when the solid–liquid interface migrates in 2D or 3D, the kinetics is also significantly controlled by the type and degree of curvature at the migrating interface.

     

Hardfacing of a Modified 9Cr–1Mo Steel Component Using a Nickel-Base Alloy

A dashpot piston made of modified 9Cr–1Mo steel is hardfaced with NiCr-B alloy by the Plasma Transferred Arc (PTA) process. During initial trials, a large number of cracks were observed in the hardface deposit when hardfacing was carried out directly on the modified 9Cr–1Mo steel substrate using a preheat temperature of 723 K. Both the deposit and the martensitic structure formed in the heat affected zone of the substrate during deposition are hard and hence were unable to absorb the thermal stresses generated, leading to cracking. Subsequently, hardfacing trials carried out with an intermediate layer of 2 mm thick Inconel-625 alloy, were successful and deposits were crack-free. Use of a relatively soft Inconel-625 between the hardface deposit and the substrate reduced martensite formation in the substrate, and thus the cracking susceptibility of the deposit.     

Study of the Gamma Radiation Induced Change on the Surface Morphology of Electroless Ni–P Deposited AISI 304 Stainless Steel

In this research electroless Ni–P coatings were deposited on AISI 304 stainless steel. Deposits have been irradiated in 30 % H₂O₂ environment with a ⁶⁰Co gamma source at a dose rate of 0.48 Gy/s at ambient temperature. The effect of gamma radiation on surface characteristics of electroless Ni–P coated AISI 304 stainless steel was investigated. Scanning electron microscopy results revealed that the Ni–P deposit was completely cracked and fragmented after gamma radiation. Energy-dispersive X-ray examination showed high oxygen and phosphorous content on the surface after gamma radiation. According to X-ray diffraction result it originated from the formation of P₂O₃ oxide on the surface after gamma radiation. It was found that gamma radiation of Ni–P deposit at H₂O₂ environment caused oxidizing of Ni–P deposit and preferential formation of P₂O₃ oxide. Atomic force microscopy images showed typical nodular structure for Ni–P deposit and clustered structure with positions breaking off between the clusters for Ni–P deposit after gamma radiation.     

Design and Achievement of Metallurgical Bonding of Mg/Al Interface Prepared by Liquid–Liquid Compound Casting via a Co-deposited Cu–Ni Alloy Coating

The metallurgical bonding of Mg/Al bimetal by liquid–liquid compound casting was realized via co-deposition Cu–Ni alloy coating. The metallurgical layer of the Mg/Al bimetal consisted of Cu solid solution, Cu₂Mg and (Al0.7Cu1.3) Mg, Mg solid solution, Al₃Ni₂, and Mg₂Cu. Vickers hardness of the interface was between 149.9 and 209 HV, which was significantly lower than those of Al–Mg intermetallic compounds. The formation mechanism of the interface was attributed to interdiffusion among AZ91D, A356, and Cu–Ni alloy coating.

     

Decelerated Coarsening of (Ti,Mo)C Particles with a Core–Shell Structure in Austenite of a Ti-Mo-Bearing Steel

The aim of this study is to reveal the effect of Mo on coarsening of (Ti, Mo)C particles in austenite of a Ti-Mo-bearing steel. (Ti, Mo)C particles with a core–shell structure including a Ti-rich core and a Ti, Mo-rich shell were directly observed using high-resolution, high-angle, angular dark-field scanning transmission electron microscopy. Coarsening of (Ti, Mo)C particles is significantly decelerated due to the formation of a Mo-enriched shell, which is expected to reduce interfacial energy.     

Microstructure of TiC–TiN–Ni–(B) cermet systems

Abstract

TiC-TiN-Ni-(B) systems were investigated to understand particle coarsening and morphology changes as a function of sintering time and compositions. In addition, the variations in the C/(C+N) ratios of Ti(C_1-xN_x) solid solutions formed in the system were studied. As expected, the particle size becomes larger with an increase in the duration of sintering. However, added boron significantly reduced the growth of particles. X-ray diffraction analysis shows that the binder phase consists largely of Ni₃B in TiC-TiN-20Ni-1B (in wt-%) system. The presence of boron in the liquid Ni seems to interfere with the dissolution of TiC and TiN and/or transport of Ti, C, and N. The effect of boron decreases as the amount of Ni binder increases. The particle morphology is found to change with variations in the C/(C+N) ratio.     

Fe–Mo–(Ni/Cu)–石墨粉末冶金复合材料的制备及组织性能研究

采用粉末冶金方法制备了Fe–Mo–Ni–石墨(Fe–Mo–Cu–graphite,FMNG)和Fe–Mo–Cu–石墨(Fe–Mo–Cu–graphite,FMCG)材料,对比研究了Ni及Cu组元对Fe–Mo–石墨材料组织、物相、硬度及抗压强度等的影响。结果表明:烧结态FMNG、FMCG材料组织主要由珠光体、铁素体、贝氏体、石墨及夹杂分布的强化相Mo_2C、Fe_3Mo_3C组成;热处理提高了FMCG/FMNG材料的硬度及抗压强度;FMCG材料的抗压强度高于FMNG材料;FMCG材料的硬度低于FMNG材料。     

Microstructure of Cast Ultrahigh Carbon Steel (UHCS) Modified via Fe–Si–Mg–Ca–RE

In this study, effect of modification treatment via Fe–Si–Mg–Ca–RE modifier on microstructure of ultrahigh carbon steel containing 1.5 wt% C was investigated. Microstructure characterization was performed by optical microscopy. It was found that as-cast proeutectoid carbide network tend to break after the modification treatment, and the carbides changed to discontinuous and spherical shape and uniformly distributed in matrix. Also, grain size, porosity and inclusions content decreased by modification treatment.     

Centrifugal Metallothermic SHS of Cast Co–Cr–Fe–Ni–Mn–(Х) Alloys

Russian Journal of Non-Ferrous Metals - A relatively new approach to obtaining metal materials containing several principal elements in equiatomic concentrations which look promising for replacing...     

Phase equilibria in W-Fe-Co-Ni system alloys. I. Alloys containing 10% (Fe + Co + Ni) at 1400–1200°C

Conclusions The isostructural intermediate -phases of Fe₇W₆ and Co₇W₆ in the W-Fe-Co system form a continuous series of solid solutions and transformation of the L + peritectic equilibrium into, the similar L + (Co₇W₆), occurring in a narrow temperature range (1640–1630°C) is observed. In the W-Fe-Co-Ni system in the 1470–1460°C range transition of the L + (Fe₇W₆)+ peritectic equilibrium into the similar. L + (Co₇W₆+ is also observed.Upon completion of crystallization and at temperatures of 1400–1200°C alloys of the primary section with 10% (Fe + Co + Ni) have a two-( + or +) or three-phase (+ +) structure. In alloys rich in iron at temperatures below 1215°C FeW may form instead of (Fe₇W₆) phase.Translated from Poroshkovaya Metallurgiya, No. 4(280), pp. 60–64, April, 1986.     

Evaluation of Microstructural, Mechanical Properties and Corrosion Behavior of AISI Type 316LN Stainless Steel and Modified 9Cr-1Mo Steel Exposed in a Dynamic Bimetallic Sodium Loop at 798 K (525?°C) for 16,000 Hours

Changes occurring in the chemical composition, microstructure, mechanical properties, and carburization behavior of type 316LN stainless steel and modified 9Cr-1Mo steel on exposure to flowing sodium at 798?K (525?°C) for 16,000?hours in a bimetallic loop are discussed in this article. Type 316LN stainless steel revealed a degraded layer of approximately 5???m depth. No significant microstructural changes were observed in the case of modified 9Cr-1Mo steel exposed to sodium. The carburization depth in type 316LN stainless steel was approximately 100???m and the surface carbon concentration was 0.374?wt?pct. In the case of modified 9Cr-1Mo steel, the carbon concentration at the surface was approximately 3.50?wt?pct and the depth of carburization was nearly 75???m. The concentration of nickel and chromium decreased from the bulk to the surface of type 316LN stainless steel, leading to the formation of a ferrite layer. The concentration of these two elements reached the original matrix concentration at around 30???m. Sodium-exposed material indicated an increase in yield strength by 10?pct and reduction in ductility by 34?pct vis-à-vis annealed material. No such changes in strength and ductility were observed in the case of modified 9Cr-1Mo steel. A decrease in impact energy was noticed for sodium-exposed type 316LN stainless steel and modified 9Cr-1Mo steel vis-à-vis as-received material.     

Electrochemical Behavior of Bulk Amorphous Steel Fe55M2Cr12Mo10B6C13Y2（M=Ni, Cu, Nb）

 Fe55Ni2Cr12Mo10B6C13Y2,Fe55Cu2Cr12Mo10B6C13Y2 and Fe55Nb2Cr12Mo10B6C13Y2 alloys with diameter of 4mm were produced by copper mold casting. The role of alloying additions (Ni, Cu or Nb) on corrosion resistance of Fe55Nb2Cr12Mo10B6C13Y2, Fe55Ni2Cr12Mo10B6C13Y2 and Fe55Cu2Cr12Mo10B6C13Y2 alloys were studied by polarization curves and electrochemical impedance spectroscopy (EIS). The results show that Fe55Ni2Cr12Mo10B6C13Y2 and Fe55Cu2Cr12Mo10B6C13Y2 alloys can be cast into bulk metallic glasses. Fe55Ni2Cr12Mo10B6C13Y2 and