The thermodynamic description of the C-Cr-Ti ternary system has been reassessed. The main reason was to adjust the solubility limit of Cr in MC (M = Cr, Ti), but also to take the solubility of Ti in M3C2 and M7C3 into account. Another reason was that the thermodynamic descriptions of all the three constituent binary systems (C-Cr, C-Ti and Cr-Ti) had been revised after the previously published description of the C-Cr-Ti system. Important metastable end-members and interaction parameters were calculated using Density Functional Theory (DFT). For fcc-CrC and Ti3C2, DFT was used together with a recently published method to calculate the molar Gibbs energy as a function of temperature (Gm(T)). For fcc-CrC also the magnetic contribution and the magnetic transition temperature, i.e. the Curie temperature (TC), were included. DFT was also used to calculate Gibbs energy of formation at 0 K for Ti7C3 and to calculate the molar excess Gibbs energy contribution, and TC, as a function of Ti composition in MC. DFT calculated parameters were compared with experiments or previous assessments. Selected experimental information from literature was then used to optimize parameters that are difficult to calculate with DFT, e.g. interaction parameters for the liquid phase and temperature dependence for interaction parameters in the solid phases. The resulting thermodynamic description, which is based on critically reviewed binary descriptions, reproduces the experimental solidification sequence, found in literature, equally well as the previous description of the C-Cr-Ti system. Furthermore, in contrast to the previous description, the new description also reproduces the most recent experimentally determined solubility of Cr in MC and takes the solubility of Ti in M3C2 and M7C3 into account. Finally the new description uses DFT calculated metastable end-members and interaction parameters, which gives more reliable predictions, especially at low temperatures.

A method for calculation of finite temperature thermodynamic properties for magnetic allotropes has been developed. The developed method is based on quasi-harmonic approximations using the Debye-Gruneisen model. Electronic contributions are included and magnetic disordering contributions are added with the empiric model often used in CALPHAD (CALculation of PHAse Diagrams) databases. The developed method also includes two new ways to estimate the Debye temperature (theta(D)(V-0)) which enables calculation of finite temperature thermodynamic properties also for allotropes that are dynamically unstable at 0 K. Also a new CALPHAD approach for estimation of Curie- (T-C) or Neel- (T-N) temperatures is presented. The developed method was used to calculate Gibbs energy as a function of temperature (G(T)) and isobaric heat capacity as a function of temperature (C-P(T)) for the body-centred-cubic (bcc), the face-centred-cubic (fcc) and the hexagonal-closed-packed (hcp) allotropes of Fe, Co and Ni. The results were compared with the SGTE Unary database. By using the developed method the phase transitions in Fe and Co were predicted. The calculations of the metastable allotropes fcc-Fe, hcp-Fe and bcc-Ni in this work indicates that the descriptions of these allotropes in the SGTE Unary database need to be updated, especially regarding the magnetic parameters. Furthermore, contradictory to previously reported results in literature, the calculations in this work show that the magnetic ground state structure of fcc-Fe is the double layer antiferromagnetic structure (AFM-D) and not a spin-spiral. The final conclusion is that by using the developed method it is possible to calculate finite temperature thermodynamic properties, not only, for stable and metastable magnetic allotropes, but also for magnetic allotropes that are dynamically unstable at 0 K, which is very important for the development of thermodynamic databases.

To understand the observed wear in WC/Co tools during machining of Ti-alloys, it is important to know which interfaces are present in the tool-workpiece contact zone. It has been shown that WC grains in contact with the workpiece form a C depleted layer consisting of BCC W, and as such, knowledge of which WC/W interfaces can be expected and which interfaces can be used as starting points for further computations are of great importance. Here, this is studied by the systematic construction of interfaces and evaluation of the work of adhesion and interfacial energies of 60,000 unique interfaces spread across six different interface systems made up of the basal and prismatic surfaces of WC and the low index surfaces of BCC W. Calculations are made using a classical approach in LAMMPS as well as subset analysis using first principles in VASP (Vienna Ab Initio Simulation Package). The results show trends as functions of strain and system size giving a large-scale overview of this system and finding the energetically preferred interface combination to be the type-I, W-terminated prismatic WC surface against the [110] surface of BCC W.