Nonferromagnetic Elinvar-Type Alloys in the Mn–Ni–Co System

Abstract

Measurements of Young’s modulus at −150∼400°C and of rigidity modulus, thermal expansion and hardness at room temperature have been carried for Mn–Ni–Co alloys subjected to cold working and varying heat treatments. An anomalous variation associated with antiferromagnetic transformation was observed in the Young’s modulus vs temperature curves for the ternary alloys which had been slowly cooled after heating at 950°C for 1 hr. The temperature coefficient of Young’s modulus is highly dependent on the metallurgical processing history, i.e. annealing, cold working and reheating after cold working or water quenching as well as the alloy composition. The existence of a positive large maximum in the temperature coefficient of Young’s modulus vs composition curves demonstrates the Elinvar characteristics of the ternary alloys. The behaviors of the rigidity modulus and its temperature coefficient are very similar to those of the Young’s modulus and its temperature coefficient. The hardness of the alloys varies in a complex manner within the order of 100∼800 in Vickers hardness. The corrosion resistivity of the alloys is very satisfactory.