Antiferromagnetic Elinvar-Type Alloys in the Mn–Cu–Mo System

Abstract

Measurements have been made of the Young’s modulus at −150∼400°C and the rigidity modulus and its temperature coefficient at room temperature for Mn–Cu–Mo alloys subjected to cold working and various heat treatments. The results of measurements show the appearance of an anomalous variation, which seems to be related to the antiferromagnetic \ ightleftarrows paramagnetic transformation, on the Young’s modulus vs composition curves for the ternary alloys in the state of slow cooling after heating at 900°C for 1 hr. In general the Young’s modulus at room temperature in the state of annealing is higher than that in state of cold working or water quenching, and its value shows the tendency to increase with rise of the reheating temperature after cold working or water quenching. The temperature coefficient of Young’s modulus undergoes a remarkable variation by annealing, cold working, water quenching, and reheating after cold working or water quenching. The temperature coefficient is also found to vary greatly with composition. There appear positive values of the temperature coefficient of Young’s modulus in the wide range of composition, proving the alloys to have the Elinvar characteristics. The changes in rigidity modulus and its temperature coefficient with composition, heat treatment and cold working closely resemble those in Young’s modulus and its temperature. The vickers hardness shows a complicated variation in the range of the order of 130∼700 with composition and the state of cold working, water quenching or thermal treatment after cold working and water quenching. The corrosion resistance of the ternary alloys is found to be fairly satisfactory.