Impact of Thermomechanical Processing on the Functional Properties of Fe–Ni–Co–Al–Ti–B Shape Memory Alloys

Abstract

Iron-based shape memory alloys (SMAs) are promising alternatives to conventional SMA candidates such as Ni–Ti regarding cost-efficiency. The present study investigates cold-rolled Fe–Ni–Co–Al–Ti–B samples subjected to different recrystallization heat treatments. The impact on microstructure and thermomechanical behavior is discussed in detail. Two distinct recrystallization heat treatment (HT) procedures were conducted. After both HTprocesses, the samples were aged at 600 ℃ for 4 h to precipitate the γ’-phase, which is crucial for the thermomechanical behavior of the material. The cold-rolled material exhibitsβ-phase, which fully dissolves during a solution annealing above 1200 ℃. In addition, a Goss-type texture has formed with the main component in {hkl} < 100 > γ. During the HTprocess, both recrystallization and grain growth occurred. Thermomechanical experiments demonstrate reversible shape memory behavior and transformation strains up to 5 % under external load during heating and cooling experiments.