Fe-Ni 2元合金のマルテンサイト変態におよぼす繰返し熱処理の影響

抄録

In order to evaluate the effect of the cyclic heat treatment on the martensitic transformation, the investigations on dilatation curves, on microstructures and on mechanical properties were carried out using the iron-nickel binary alloys containing 24.50 to 30.70 atomic per cent nickel. The Ms temperature lowered with the increase in the numbers of cyclic heat treatment so that the amount of martensitic transformation also decreased. The optical and electron microstructures of martensite after the cyclic heat treatment consisted of finer martensite platelets and of high dislocation density. The hardness and tensile strength of austenite were remarkably increased by the cyclic heat treatment at the early stage, but in the case of the martensite they were not remarkably increased. The driving force necessary for initiating martensitic transformation increased with the increase in the numbers of cyclic heat treatment. It was suggested that these results will be caused by a mechanism based on the concept of the work hardening of austenite due to the cyclic heat treatment.