Weiwei Zhang Receives JPED Editor Choice Award

Weiwei Zhang, PhD, Material Scientist at Thermo-Calc Software, was awarded for her paper “Thermodynamic Modeling of the La-Co-O System” (Authors: Weiwei Zhang, Erwin Povoden-Karadeniz, Huixia Xu & Ming Chen). It was recognized as one of six papers in the annual JPED Editors’ Choice Awards. Dr. Zhang’s paper is based on a chapter from her PhD thesis and was edited for publication in the “Journal of Phase Equilibria and Diffusion”.

Weiwei Zhang
Weiwei Zhang, PhD, Material Scientist at Thermo-Calc Software
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Complimentary Thermo-Calc Licenses Support Research Beneficial for Sustainability in Transport and Energy Sector

Gourav Mundhra, PHD student

Gourav Mundhra is a joint PhD student in the Department of Metallurgical and Materials Engineering at the Indian Institute of Technology Madras and the Department of Materials Science and Engineering at the National Tsing Hua University. He resides in India and is the lead author of the article “Design of a novel Al–Ti–Zr light-weight alloy: CALPHAD and experiments” which was recently published in the Journal of Alloys and Compounds by Elsevier.

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Applications of Thermo-Calc to Steel Making Processes Described in New Paper

A paper was recently published as part of the TMS Proceedings 11th International Symposium on High Temperature Metallurgical Processing which describes in detail how Thermo-Calc can be applied to steel making processes for new and existing steel grades using the new Process Metallurgy Module, which was introduced last year in Thermo-Calc 2019b. The paper, titled The application of an effective equilibrium reaction zone model based on CALPHAD thermodynamics to steel making, describes how an expansion to the module, coming this year, incorporates a kinetic model of the steelmaking process based on the concept of effective equilibrium reaction zones (EERZ) and gives a detailed example of how this module can be applied to the entire steelmaking process using a real case from a steel plant in Ontario, Canda.  

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Segregation in Continuously Cast Steel Billets Investigated using Thermo-Calc and DICTRA

Steel billets with text that reads Thermo-Calc and DICTRA used for investigating segregation in continuously cast steel billets.

A paper published in IOP Conference Series: Materials Science and Engineering investigates various fundamental concepts that are at play during the solidification of continuously cast steel billets at different cooling rates. The simulations in the paper, Continuous Casting of High Carbon Steel: How Does Hard Cooling Influence Solidification, Micro and Macro Segregation?, were performed with the Thermo-Calc software package to investigate solidification as well as micro and macro segregation of steel billets from continuous casting. Thermo-Calc, together with the TCFE database, was used to calculate different steel properties and perform Scheil solidification simulations to compare simplified C80D steels with no carbon diffusion and fast carbon diffusion. The calculated steel properties were then used in the solidification simulation in CHILL (developed by the SMS Group). With information from the CHILL simulations, the diffusion equations were solved using the Diffusion module (DICTRA) together with the free mobility database MFEDEMO. Thermo-Calc was also used to calculate the driving forces for diffusion with the free database FEDEMO.

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Thermo-Calc Used to Predict Phase Fractions when Partially Substituting Cobalt

Cobalt symbol on blue background with the words Thermo-Calc used to predict phase fractions when Partially Substituting Cobalt

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.

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Thermo-Calc used to Estimate Critical Temperatures in Type 410 Steels

A person welding with the words Thermo-Calc used to estimate critical temperatures in type 410 steels written on top

In the paper Alloy Composition and Critical Temperatures in Type 410 Steel Welds, Thermo-Calc was used to evaluate the effect of alloy composition on critical temperatures (A1 and A3) in Type 410 steels.

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.

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Paper Investigates Carbon Behavior in the Heat-Affected Zone of Grade 91 Steel using DICTRA

A macro view of the weld metal, heat affected zone and base metal from section with the words "investigation of carbon behavior in the heat-affected zone of grade 91 steel using DICTRA".
A macro view of the weld metal, heat affected zone and base metal from section.

In a paper out of Ohio State University, the mechanism of δ-ferrite retention in the coarse-grained heat-affected zone is studied.

The 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 welds weaker.

Creep 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 filler metal.

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Applications of Thermo-Calc to Additive Manufacturing of Metals

A few pieces of 3D printed metal components.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