A new publication in Acta Materialia investigates the possibility to partially substitute Cobalt with entropic alloys, focusing on the relative stabilities of the fcc and hcp structures.
Cobalt-base alloys are important for high temperature applications due to their possibility to form duplex fcc + hcp structures and their low stacking fault energy. However, there is an interest in substituting cobalt for economical, ethical and health reasons.
Both the thermodynamic and kinetic calculations in this publication were performed with Thermo-Calc software and the Diffusion module (DICTRA) together with the thermodynamic database TCHEA and the kinetic database MOBNI. Thermo-Calc was used to predict the phase fractions of fcc and hcp which were compared with experimental results. In the article, it is stated that the calculated thermodynamic values correlate relatively well with the experimental values. The authors concluded that designing duplex fcc + hcp Co-based alloys with computational tools is feasible.
Type 410 steels are typically welded by using consumables with matching composition. However, this type of steel has shown to have poor weldability which is related to formation of hard and brittle martensite in the weld zone, hydrogen-included cracking or retention of δ-ferrite which affects the toughness. One theory that explains the inconsistent toughness is that the wide composition ranges of the base metal results in wide variations of the A1-temperature. In the paper, this theory was investigated with the design of experiment (DoE) approach using Thermo-Calc to perform thermodynamic simulations. Thermo-Calc together with the TCFE8 database was used to predict A1 and A3 temperatures for various compositions.
efficiency of fossil-fired and nuclear power plants has caused raised operating
temperatures, which requires use of creep-resistant stainless steels in the
hottest regions of the plant. Grade 91 steels are used in the lower-temperature
heat recovery steam generators. To be able to join the high- and
low-temperature sections, dissimilar metal welds (DMWs) are necessary. The
problem with using DMWs is that it often results in extensive carbon diffusion
near the fusion boundary which creates brittle and large carbides that make the
strength-enhanced ferritic (CSEF) steels are today welded with Ni-based filler
metals to reduce the carbon diffusion between the dissimilar steels, which
reduces the formation of hard and soft zones that negatively affects the creep
strength. However, the high concentration of carbide forming elements in
Ni-based alloys still creates a driving force for carbon diffusion toward the
Additive manufacturing of metals is transforming materials design and processing in ways unimaginable even 10 years ago, offering the freedom to produce complex parts without the restraints of traditional manufacturing.
However, Additive Manufacturing is a complex process and the mechanical properties of these materials and the parameters which control their reproducibility are not yet well understood. For example, additive processes are typically associated with rapid cooling rates and large thermal gradients. This can give rise to high levels of residual stress in the final part and local inhomogeneities in alloy composition during solidification. Also, the effect of multiple thermal cycles on material properties is sometimes unknown and typically does not result in the properties of a similar cast or wrought metal.
A lot of research is now being published in this area by members of our community using Thermo-Calc and we want to share some of this work with you. Below you will find a sampling of some of the work that is being done using Thermo-Calc and our add-on modules for diffusion and precipitation to research additive manufacturing of metals.Continue reading →
A new publication in the May issue of Acta Materialia uses the Diffusion module (DICTRA) with TCNI8, the Ni-based superalloys database, to investigate how additive manufacturing can improve heat treatment processes in the Ni-based superalloy Inconel 625. Continue reading →
A paper published in the March issue of the Journal CALPHADrelies on Thermo-Calc to analyse three methods used to increase the efficiency of computational materials software when applied to high temperature industrial alloys. Continue reading →
In a paper published in the January 2016 issue of Journal of Phase Equilibria and Diffusion, Vol. 37 No. 2 2016, the homogenization model within DICTRA together with the TCNI and MOBNI databases were used to model the interdiffusion processes in the Ni-based superalloy CMSX-10 and was shown to have good agreement with experimental values. Continue reading →
In a 2015 issue of Metallurgical and Materials Transactions A a group at Michigan University, Department of Materials Science & Engineering used TC-Toolbox for MATLAB® in conjunction with Thermo-Calc to optimise a nickel-based alloy, resulting in a lower cost alloy with 25% improvement in properties when assessed with their utility function. Continue reading →
ABM has released a special issue of the journal TMM comprised entirely of articles relating to Phase Diagrams and Computational Thermodynamics. The special edition includes articles ranging from the fundamentals of CALPHAD to examples of the use of ab-initio calculations and more. Continue reading →
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