Consistency in material properties and performance is critical to the aerospace industry. Small variations in material chemistry or process windows can have a large impact on the final part performance. The ability to predict and adjust for these variations can reduce scrap and part re-work. Metallurgists and process engineers responsible for heat treatments must adapt their processes when input variables change.
In an article recently published in “Heat Treat Today”, Adam Hope and Paul Mason from Thermo-Calc Software Inc, discuss how modeling and simulation tools such as Thermo-Calc can support engineers in their research.
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.
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.
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
Thermo-Calc Software recently published a new comprehensive tutorial which teaches about the role of diffusion in materials and how the Diffusion module (DICTRA) can be applied to materials design and processing, called The Role of Diffusion in Materials.
A basic exercise at the beginning of the tutorial walks users through how to assess whether there is any leakage from a tube at a power plant. The exercises get increasingly complex as the tutorial progresses.
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 →
The Diffusion module (DICTRA), the software program for accurate simulation of diffusion controlled reactions in multicomponent alloy systems, is now available in the graphical mode beginning with Thermo-Calc 2017a, making it easier than ever for users to begin making diffusion simulations. 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 →