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A first-principles based description of the Hf-Ni system supported by high-temperature synchrotron experiments
- Source :
- Thermochimica Acta. 668:142-151
- Publication Year :
- 2018
- Publisher :
- Elsevier BV, 2018.
-
Abstract
- Hf-Ni is an important binary system for high temperature alloys and shape memory alloys which has been investigated several times in the literature but often using samples of Hf contaminated by Zr. The thermodynamics of this system are remodeled in this work based on first-principles calculations and additional experiments using Hf with relatively low Zr contamination (0.25 wt. %). Diffusion couples in the Ni-rich portion of the Hf-Ni system heat treated at 1173, 1273 and 1373 K are used to measure phase stability and Hf solubility in the fcc phase. The solubility observed in fcc Ni from Ni/Ni50Hf50 (at.%) diffusion couples is larger than that observed in previous experiments. These results are the only source fit to during modeling of the fcc solubility to mitigate effects from Zr contamination. Data in the literature suggests that the high temperature crystal structure of the B33 NiHf phase is, in fact, the B2 structure. High temperature synchrotron measurements provide confirmation of this crystal structure. Modeling of the B2 phase was aided by first-principles calculations using special quasi-random structures (SQS). The present CALPHAD model will prove useful when designing shape memory alloys containing Hf and when modeling the Hf activity in Ni-base high temperature alloys.
- Subjects :
- 010302 applied physics
Work (thermodynamics)
Materials science
Diffusion
Thermodynamics
02 engineering and technology
Crystal structure
021001 nanoscience & nanotechnology
Condensed Matter Physics
01 natural sciences
Synchrotron
law.invention
law
Phase (matter)
0103 physical sciences
Binary system
Physical and Theoretical Chemistry
Solubility
0210 nano-technology
Instrumentation
CALPHAD
Subjects
Details
- ISSN :
- 00406031
- Volume :
- 668
- Database :
- OpenAIRE
- Journal :
- Thermochimica Acta
- Accession number :
- edsair.doi...........55800d47c5a181c06d1b3289f6e89696