KeywordAlloying strategy; Amorphous alloys; Fcc single phase; Gibbs phase rule; High entropy alloys; Icosahedral phase; Multicomponent alloys; Quasicrystals; Solid solubility; Al-based alloys; Scale icosahedral phase; Equiatomic substitution; Mechanical properties; Structural characterisation; Crystallisation behaviour; Elevated temperature; Amorphous alloys; High-strength; Microstructure
Rights(c) 2014 The Author. This is an Open Access article distributed under the Creative Commons CC-BY license (https://creativecommons.org/licenses/by-nc-sa/3.0/)
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AbstractThis paper describes some underlying principles of multicomponent and high entropy alloys, and gives some examples of these materials. Different types of multicomponent alloy and different methods of accessing multicomponent phase space are discussed. The alloys were manufactured by conventional and high speed solidification techniques, and their macroscopic, microscopic and nanoscale structures were studied by optical, X-ray and electron microscope methods. They exhibit a variety of amorphous, quasicrystalline, dendritic and eutectic structures.
CitationCantor B (2014) Multicomponent and High Entropy Alloys. Entropy. 16(9): 4749-4768.
Link to publisher’s versionhttp://dx.doi.org/10.3390/e16094749
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Design and processing of low alloy high carbon steels by powder metallurgy. P/M processing and liquid phase sintering of newly designed low-alloy high carbon steels based on Fe-0.85Mo-C-Si-Mn with high toughness and strength.Wronski, Andrew S.; Abosbaia, Alhadi A.S. (University of BradfordSchool of Engineering, Design and Technology, 2011-03-31)The work presented has the ultimate aim to increase dynamic mechanical properties by improvements in density and optimisation of microstructure of ultra high carbon PM steels by careful selection of processes, i.e. mixing, binding, alloying, heating profile and intelligent heat treatment. ThermoCalc modelling was employed to predict liquid phase amounts for two different powder grades, Astaloy 85Mo or Astaloy CrL with additive elements such as (0.4-0.6wt%)Si, (1.2-1.4wt%)C and (1-1.5wt%)Mn, in the sintering temperature range 1285-1300ºC and such powder mixes were pressed and liquid phase sintered. In high-C steels carbide networks form at the prior particle boundaries, leading to brittleness, unless the steel is heat-treated. To assist the breaking up of these continuous carbide networks, 0.4-0.6% silicon, in the form of silicon carbide, was added. The water gas shift reaction (C + H2O = CO + H2, start from ~500ºC) and Boudouard reaction (from ~500ºC complete ~930ºC) form CO gas in the early part of sintering and can lead to large porosity, which lowers mechanical properties. With the use of careful powder drying, low dew point atmospheres and optimisation of heating profiles, densities in excess of 7.70g/cm3 were attained. The brittle microstructure, containing carbide networks and free of cracks, is transformed by intelligent heat treatment to a tougher one of ferrite plus sub-micron spheroidised carbides. This gives the potential for production of components, which are both tough and suitable for sizing to improve dimensional tolerance. Yield strengths up to 410 MPa, fracture strengths up to 950 MPa and strains of up to 16 % were attained. Forging experiments were subsequently carried out for spheroidised specimens of Fe-0.85Mo+06Si+1.4C, for different strain rates of 10-3, 10-2, 10-1 and 1sec-1 and heated in argon to 700¿C, density ~7.8g/cm3 and 769 MPa yield strength were obtained.
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Selective laser melting of prealloyed high alloy steel powder bedsWright, Christopher S.; Youseffi, Mansour; Akhtar, S.P; Childs, T.H.C.; Hauser, C.; Fox, P.; Xie, J. (2006)This paper presents the results of a recent comprehensive investigation of selective laser melting (slm) of prealloyed gas and water atomised M2 and H13 tool steel powders. The objective of the study was to establish the parameters that control the densification of single and multiple layers with the aim of producing high density parts without the need for infiltration. Powders were processed using continuous wave (CW) CO2 and Nd:YAG lasers. Relationships between alloy composition, powder particle size and shape, flowability, microstructure (phases present, their size, morphology and distribution), track morphology, post scanned density, surface finish and scan conditions (Laser power, spot size and scan speed) are discussed for single track, single layer and multi-layer (up to 25 layers) constructions. Processing with a Nd:YAG laser with powders placed on substrates rather than on a loose powder bed gave more stable builds than with the CO2 laser. Using the Nd:YAG laser densities up to ~90% relative were possible with H13 powder compared with a maximum of ~70% for M2 in multi-layer builds. Maximum density achieved with CW CO2 processing was only ~60%, irrespective of powder composition. The paper compares the processibility of these materials with stainless steel powders processed to higher densities (up to 99% relative) under similar conditions. The results of the work show that a crucial factor for high density processing is melt pool wettability and this is controlled largely by carbon content; low carbon contents producing better wettability, flatter tracks and higher densities. The significance of this observation for the processing high alloy steels by slm will be discussed.