Composition and Crystalline Structure of Ternary Phases in the Ta–Ni–Al System

Russian Journal of Non-Ferrous Metals - The composition and crystal structure of compounds produced by self-propagating high-temperature synthesis (SHS) from the 5Ta–2Ni–3Al (at %)...     

Glass-Forming Ability of Mg–Cu–Ni–Gd Bulk Metallic Glasses with High Strength

The glass-forming ability (GFA) of Mg–Cu–Ni–Gd alloy system was evaluated using copper mold casting. A three-dimensional composition map of Mg–Cu–Ni–Gd system with GFA over 6 mm was revealed, confirming that the Ni addition decreased the GFA of Mg–Cu–Gd system. The maximum Ni tolerance was about 6 at.% for the Mg–Cu–Ni–Gd BMGs with GFA over 6 mm. The compressive tests displayed that the Ni addition as small as 3.45 at.% could result in higher strength for the Mg–Cu–Gd BMGs. The Mg–Cu–Ni–Gd system with small Ni content can be balanced candidates for the Mg-based BMGs with both acceptable GFA and high strength.     

Weldability and Microstructure of Nickel-Silicon Based Alloys

The NiSix based alloy typically has poor weldability due to its lower ductility. A limited amount of work has been performed on the weldability of NiSix based alloys. Therefore, the effect of heat treatment and welding parameters on weldability of the alloys, and the relationship between the weldability and microstructure were studied. The results show that the as-cast Ni-Si-Nb-B alloy （Ni 76. 5%, Si 20%, Nb 3%, and B 0. 5%） could be successfully welded after preheating at 600 ℃. The welding procedure should be performed on the alloys before any heat treatment and a preheating at 600 ℃ should be used. The fusion zone is harder than the matrix due to a large amount of 7 phase and a finer microstructure. The cracks are predominantly intergranular in heat affected zone and associated with the needle-like ）, phase. The heat treatment before welding increases the tendency of cracking in the fusion zone.     

Characterization of Fe–C–Cr Based Hardfacing Alloys

Hardfacing is one of the adaptable methods that can build up the hard and wear resistant surface layer of different materials on the surface of substrate material. It helps them withstand wear, as well as prevent corrosion and high temperature oxidation. In the present investigation three different types of Fe–C–Cr based hardfacing electrodes with varying chemical compositions were deposited on ASTM A36 steel substrate by using manual metal arc welding (MMAW) process. ASTM A36 steel was selected as a base material after consulting with Pressure and Process Boilers, Saharanpur (India), which is a leading manufacturer of boilers. ASTM A36 steel is mostly used by this company for the production of induced draft fans. MMAW process with direct current constant current type power source was used to deposit the hardfaced layers of uniform quality. Straight polarity was used for MMAW process so that more of the arc heat should be concentrated on the electrode. The hardfaced samples were characterized using various characterization techniques and the results of the same were also outlined in the present investigation.     

Research on Nitrogen Solubility of Fe–Cr–Mn–V–N System Alloys in Liquid and Solid Phases

In this paper, the thermodynamic model of nitrogen solubility in vanadium nitrogen microalloyed high strength weathering steels of Fe–Cr–Mn–V–N system, according to Hillert’s model for Gibbs energy of its various phases, was established and validated. In the model, the effect of the nitrogen partial pressure on the activity coefficient and the lattice structure characteristics of the vanadium nitrogen precipitated phase were considered. It would be of guiding significance for the design and smelting of Fe–Cr–Mn–V–N system alloys. Based on the established model, the nitrogen contents in \(\delta\), \(\gamma\), \(\alpha\) phase and liquid were calculated as a function of the temperature for Fe–Cr–Mn–V–N system alloys. The results show that: first, the maximum solubility of nitrogen in the solidification process is obviously affected by the phase transition when there is a sudden change in the solubility of nitrogen at the phase transition point. The maximum nitrogen solubility of the molten steel in the delta phase region determines whether nitrogen bubbles are formed during the solidification process. The nitrogen solubility is lowest in the solid–liquid region (about 1673 K). Secondly, the increase of Cr and Mn content is beneficial to improve nitrogen solubility in liquid and solid phases. However, the increase of V content mainly affects the nitrogen solubility in the solid phase because the nitrogen in this temperature range is precipitated in the form of vanadium nitride, as the second phase plays a role in strengthening. In addition, the alloying element Mn has a significant effect on nitrogen solubility since the Mn element is the promoting element of austenitic formation. During the solidification process, the delta ferrite region gradually reduces and may disappear with increasing Mn content. Therefore, increasing the Mn content of the alloy system in the design of alloy composition, can reduce the precipitation trend of the nitrogen during the solidification process, which can effectively avoid bubble formation in high nitrogen weathering steels. Lastly, with the increase in the nitrogen partial pressure, the solubility of nitrogen increases during the liquid and solid phases.     

Iron–Chromium Precursors for Hard-Magnetic Fe–Cr–Co Alloys

The effect of the chromium concentration on the magnetic properties of Fe–Cr precursors for hard-magnetic Fe–Cr–Co materials is studied. Nitrogen used as a sintering atmosphere and a long annealing time enhance are found to increase the coercive force H_c of the materials. The phase formation in Fe–30% Cr alloys is traced during heat treatment in nitrogen and argon atmosphere using thermal analysis.     

Effects of Microalloying on Glass Forming Ability and Thermodynamic Fragility of Cu-Pr-Based Amorphous Alloys

The effects of microalloying of Ti and B on the glass formation of Cu60Pr30Ni10Al10-2xTixBx（x = 0, 0.05% （atom fraction）） amorphous alloys was investigated using differential scanning calorimetry （DSC） and X-ray diffraction （XRD）. XRD analysis showed that mieroalloying with 0.05% Ti and 0.05% B improved the glass forming ability （GFA）. The smaller difference in the Gibbs free energy between the liquid and crystalline states at the glass transition temperature （△G1-X（Tg）） and the smaller thermodynamic fragility index （△Sf/Tm, where ASf is the entropy of fusion, and Tm is the melting temperature） after mieroalloying correlated with the higher GFA.     

Phase Structure and Electrochemical Properties of RE-Mg Based Composite Hydrogen Storage Alloys

Rareearth basedAB5 typealloy ,akindofhy drogenstoragealloyusedasnegativeelectrodemateri alsofthenickel/metalhydride (Ni/MH )secondarybattery ,haseasyinitialactivation ,longcyclelifeandlowcost ,butstillasmalldischargecapacity ,poorhigh ratedischargeability(HRD)andpoorpropertiesatlowtemperature[1,2 ] .Therefore ,howtoincreaseitsdischargecapacityandtoimproveotherelectrochemi calpropertiesismeaningfulbothintheoryandinpracticalapplication .Mg basedhydrogenstorageal loysareremarkablebecauseofitsr…     

Effect of Ti Addition and Microstructural Evolution on Toughening and Strengthening Behavior of as Cast or Annealed Nb–Si–Mo Based Hypoeutectic and Hypereutectic Alloys

Room temperature fracture toughness along with compressive deformation behavior at both room and high temperatures (900 °C, 1000 °C and 1100 °C) has been evaluated for ternary or quaternary hypoeutectic (Nb–12Si–5Mo and Nb–12Si–5Mo–20Ti) and hypereutectic (Nb–19Si–5Mo and Nb–19Si–5Mo–20Ti) Nb-silicide based intermetallic alloys to examine the effects of composition, microstructure, and annealing (100 hours at 1500 °C). On Ti-addition and annealing, the fracture toughness has increased by up to ~ 75 and ~ 63 pct, respectively with ~ 14 MPa√m being recorded for the annealed Nb–12Si–5Mo–20Ti alloy. Toughening is ascribed to formation of non-lamellar eutectic with coarse Nb_ss, which contributes to crack path tortuosity by bridging, arrest, branching and deflection of cracks. The room temperature compressive strengths are found as ~ 2200 to 2400 MPa for as-cast alloys, and ~ 1700 to 2000 MPa after annealing with the strength reduction being higher for the hypoeutectic compositions due to larger Nb_ss content. Further, the compressive ductility has varied from 5.7 to 6.5 pct. The fracture surfaces obtained from room temperature compression tests have revealed evidence of brittle failure with cleavage facets and river patterns in Nb_ss along with its decohesion at non-lamellar eutectic. The compressive yield stress decreases with increase in test temperature, with the hypoeutectic alloys exhibiting higher strength retention indicating the predominant role of solid solution strengthening of Nb_ss. The flow curves obtained from high temperature compression tests show initial work hardening, followed by a steady state regime indicating dynamic recovery involving the formation of low angle grain boundaries in the Nb_ss, as confirmed by electron backscattered diffraction of the annealed Nb–12Si–5Mo alloy compression tested at 1100 °C.

     

Cerium Effect on the Phase Composition and Crystallization Behavior of Aluminum Casting Alloys Based on the Al–Mg–Si System

Russian Journal of Non-Ferrous Metals - Using a Thermo-Calc software package (TCAl4.0 database), unexplored data concerning the phase composition and crystallization behavior of...     

Developing Temperature–Time and Pressure–Time Diagrams for Diffusion Bonding AZ31B Magnesium and AA6061 Aluminium Alloys

Diffusion bonding is a suitable process for joining dissimilar materials without much difficulty. In this investigation, an attempt was made to develop temperature–time and pressure–time diagrams for effective diffusion bonding of AZ31B magnesium and AA6061 aluminium alloys. The bonding quality of the joints was checked by microstructure analysis, lap shear tensile testing and ram tensile testing. Based on the results, temperature–time and pressure–time diagrams were constructed and these diagrams will act as reference maps for selecting appropriate process parameters to get quality bonds.     

The Synthesis of Cast Materials Based on the MAX Phases in a Cr–Ti–Al–C System

Russian Journal of Non-Ferrous Metals - Two variants of the self-propagating high-temperature synthesis (SHS) process, namely, SHS from elements and SHS metallurgy, are combined to obtain cast...     

Effect of Impurities and Cerium on Stress Concentration Sensitivity of Al-Li Based Alloys

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