Phase equilibria and thermodynamic re-assessment of the Cu–Ti system

Several as-cast and annealed Cu–Ti alloys were prepared for microstructural, compositional, structural and thermal characterizations. The formation of CuTi₂ was congruent and CuTi₃ was not found in both as-cast and annealed specimens. The temperatures of nine invariant reactions were determined. The Cu–Ti system was thermodynamically re-assessed according to the experimental phase equilibria and thermochemical properties from this work and the literature. The solution phases Liquid (L), fcc-A1 (Cu), bcc-A2 (βTi) and hcp-A3 (αTi) were treated as substitutional ones. The intermetallics compounds Cu₂Ti, Cu₃Ti₂, Cu₄Ti₃ and CuTi₂ with negligible solubility were described as line ones with the formula Cu_pTi_q, while βCu₄Ti and CuTi with remarkable solubility were modeled with the formula (Cu,Ti)_r(Cu,Ti)_s. A group of reliable thermodynamic parameters of the Cu–Ti system were obtained. The calculated results agreed reasonably well with the experimental ones.     

Genomic materials design: CALculation of PHAse Dynamics

The CALPHAD system of fundamental phase-level databases, now known as the Materials Genome, has enabled a mature technology of computational materials design and qualification that has already met the acceleration goals of the national Materials Genome Initiative. As first commercialized by QuesTek Innovations, the methodology combines efficient genomic-level parametric design of new material composition and process specifications with multidisciplinary simulation-based forecasting of manufacturing variation, integrating efficient uncertainty management. Recent projects demonstrated under the multi-institutional CHiMaD Design Center notably include novel alloys designed specifically for additive manufacturing. With the proven success of the CALPHAD-based Materials Genome technology, current university research emphasizes new methodologies for affordable accelerated expansion of more accurate CALPHAD databases. Rapid adoption of these new capabilities by US apex corporations has compressed the materials design and development cycle to under 2 years, enabling a new “materials concurrency” integrated into a new level of concurrent engineering supporting an unprecedented level of manufacturing innovation.     

CALPHAD and the materials genome A 10 year anniversary

The materials genome initiative was announced by US President Obama 2011. Its actual meaning was initially rather unclear and it seemed as it could contain everything. Nevertheless, in their Scripta paper 2014 Kaufman and Ågren argued that the materials genome, analogously with biological genomes, should be defined as a set of information (databases) allowing prediction of materials structure as well as its response to processing and usage conditions. It thus seemed natural that CALPHAD thermodynamics and kinetics should play an essential role.In the present paper the role of CALPHAD as a way of processing different kind of materials data will be emphasized. The extension from thermochemistry to other properties, industrial applications and extrapolation far from equilibrium will be reviewed.     

Experimental investigation and thermodynamic modeling of the Cr–Zr–Si system

The phase equilibria of the Cr–Zr–Si ternary system were studied combined with the key experiments and thermodynamic assessment. Thirty-five ternary alloys were prepared to determine the isothermal sections at 900 and 1000 °C by means of X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS). Five ternary compounds, i.e., τ₁ (CrSi₂Zr), τ₂ (Cr₄Si₅Zr₂), τ₃ (Cr₄Si₇Zr₄), τ₄ (CrSiZr) and τ₅ (Cr₃SiZr₂), were confirmed. The solubilities of the third element in binary compounds were determined. Based on the experimental phase equilibria data available in the present work and the literature, as well as the thermodynamic parameters of constitutive binary systems, the Cr–Zr–Si system was evaluated by using the CALPHAD (CALculation of PHAse Diagram) method. A set of self-consistent thermodynamic parameters was obtained. Three isothermal sections and liquidus projection were calculated and the reaction scheme was constructed. The calculated results are in agreement with the experimental data.