Nonmagnetic Elinvar-Type Alloys in the Mn-Ni-Fe System

Abstract

Measurements of Young’s modulus at −150∼400°C and rigidity modulus, thermal expansion and hardness at room temperature have been carried out with Mn-Ni-Fe alloys subjected to a various procedures of heat treatment and cold working. In Young’s modulus vs temperature curves, the ternary alloys slowly cooled after heating for 1 hr at 950°C showed distinct anomalous changes related to the antiferromagnetic\ ightleftarrowsparamagnetic transformation. Young’s modulus at room temperature showed no remarkable difference by the annealed, cold worked or water quenched states, but the value tended to increase with increasing manganese or iron contents. The temperature coefficient of Young’s modulus showed a wide variation with annealing, water quenching, cold working, and reheating after water quenching or cold working, and also with alloy composition. The temperature coefficient of Young’s modulus as a function of composition exhibited a large positive maximum, thus showing the Elinvar property. The variations in rigidity modulus and its temperature coefficient showed a close similarity to those in Young’s modulus and its temperature coefficient. The hardness showed a very complicated change with the process of heat treatment, cold reduction rate and alloy composition, showing the Vickers hardness of about 100 to 900. Further, the corrosion resistance of Mn-Ni-Fe alloys is fairly large.