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Applied Physics Letters 80 (7): 1186-1188 (2002)

Thermodynamic stability and diffusivity of near-equiatomic Ni-Mn alloys

Ling Ding , Peter F Ladwig , Xinyan Yan , Y A Chang
The equilibrium phase diagram of the nickel-manganese system is determined between 500 and 850C, in the composition range between 25 and 70 at.% Ni. A combination of electron probe microanalysis, x-ray diffraction, and optical microscopy was employed to analyze 47 samples that were annealed anywhere from three to seven months. The equiatomic, antiferromagnetic, L10-NiMn phase that is of considerable technological interest was found to exist continuously between 500 and 700C. No other intermediate phases were found in this study at low temperatures. These results are in contrast to the currently accepted phase diagram published in most handbooks. A hot-isobaric-pressing method was used to initially bond samples that were subsequently used to determine interdiffusion coefficients in the Ni-Mn system at 650C. The Boltzmann-Matano method [T. Heumann, Z. Phys. Chem. 201, 168 (1952)] allowed the calculation of these interdiffusion coefficients across the -Mn, -Mn, -Mn, L10-NiMn, and -Ni phases. 2002 American Institute of Physics.
ISSN: 00036951     
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