1986 Volume 27 Issue 6 Pages 469-475
The thermal expansion, magnetic properties, hardness and workability were investigated in Mn-22%Ge based ternary ε phase alloys containing noble metals in groups VIIA, VIII and IB of the periodic table. In the thermal expansion curves of the ternary alloys there appears a minimum corresponding to the Néel point of the ε phase, showing the Invar characteristics below this temperature. The thermal expansion coefficient of the ternary alloys in the vicinity of room temperature shows the zero or a negative value. The spontaneous volume magnetostriction of Mn-22%Ge-0.9%Ir, −1.7%Ag and −0.9%Au alloys at 77 K is about 1.3×10−2. The value is hardly affected by the additions and is nearly equal to those of a Mn-22%Ge binary alloy and Invar-type Fe–Ni or Fe–Pt alloys. The magnetization of the ternary alloys shows almost the same temperature dependence as that of the Mn-22%Ge binary alloy which shows a parasitic ferromagnetism. The magnetization at T⁄TN=0.65 decreases with increase of the additions except Ag. The Néel point of the ε phase is scarcely affected by the additions except Ir, Pt and Re.
The Vickers hardness of almost all ternary alloys containing the noble metals less than 2% shows a value lower than that of Mn–Ge alloys, and they are superior in workabilities such as cutting and forging to the binary alloys.
