Hakaru Masumoto1, Michio Kikuchi1 and Takafumi Nakayama1
1The Research Institute of Electric and Magnetic Alloys, 2 Yagiyama-minami, Sendai 982
Young's modulus, thermal expansion and magnetization at 120--700 K and crystal structure at room temperature were investigated for annealed Mn-Ge-Fe alloys with various crystal structures such as β+γ , γ+ε and ε phases. Young's modulus vs temperature curves of the ternary alloys consisting of β+γ and of γ phase show a reversible change at a heating and cooling rate of about 27.8×10-3 K/s, and have distinct minimum and maximum corresponding to the Néel point of γ phase TN(γ) and β \rightleftarrows γ reversible transformation point Tt below about 10 at%Fe, and the alloys containing Fe above the same amount show only TN(γ). The Elinvar characteristics appears around the temperatures which correspond to a minimum or a maximum of Young's modulus vs temperature curves. However, Young's modulus of ternary alloys consisting of γ+ε and of ε phases shows minimum point at TN(ε) or TN(γ), and the Elinvar characteristics around these temperatures is weakened rapidly with increasing Fe content.
The composition range with about zero or -20×10-5 of the temperature coefficient of Young's modulus is relatively narrow and extends to the composition of Fe-70 at%Mn. This composition area has no relation to that of Fe-Mn-Ge ternary alloys reported previously.
Elinvar, Young's modulns, thermal expansion, manganese-germanium alloys, manganese-germanium-iron alloys, antiferromagnetism, hexagonal alloys
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