インバー型Mn-Ge基3元合金の弾性特性および熱膨張特性

Abstract

Magnetization, Young’s modulus and thermal expansion at 150-600 K and crystal structures at room temperature were investigated for Mn-Ge based ternary alloys containing Ti, V or Cr less than 14% which have various structures such as γ(14%Ge), γ+ε(16-20%Ge) and ε(22%Ge) phases.Magnetization value of the ternary alloys are at the most 0.4-0.5×10−6 Wb·m·kg−1 in the range of measured temperatures. Temperature dependence of magnetization of the ternary alloys shows a similar tendency to that of the basal binary alloys and distinct variations at Tt, TN(ε) and/or TN(γ) corresponding to the β\ ightleftarrowsγ or β\ ightleftarrowsε reversible phase transformation, antiferromagnetic Néel point of the ε phase and that of the γ phase, respectively. At each point of Tt, TN(ε) and TN(γ), both Young’s modulus and thermal expansion of the ternary alloys show distinct variations. Elinvar characteristic is observed in the temperature range between Tt and TN(ε) or in the range below TN(γ), and a small thermal expansion coefficient is obtained in the temperature range below TN(ε) for the alloys having an ε or ε-rich phase. A very small temperature coefficient of the Young’s modulus in the vicinity of room temperature is obtained in the wider composition range for the Mn-Ge-Ti system than that of the alloys containing V or Cr. Unlike the case of elasticity, Mn-Ge-Cr alloys show a small thermal expansion coefficient in the wider composition range than that of other alloys. In the Mn-Ge-V alloys, there are some composition ranges in which both a very small thermal expansion coefficient and a small temperature coefficient of Young’s modulus are observed in the vicinity of room temperature. Therefore, the temperature coefficient of the ultrasonic delay time shows a relatively small value.