Shape Memory and Mechanical Properties of Cold Rolled and Annealed Fe-17Mn-5Si-5Cr-4Ni-1Ti-0.3C Alloy.

Dohyung Kim,Kinam Hong,Jeesoo Sim,Junghoon Lee,Wookjin Lee

doi:10.3390/ma14020255

Abstract

In the present study, the shape, memory, and mechanical properties of cold-rolled and annealed Fe-17Mn-5Si-5Cr-4Ni-1Ti-0.3C (wt.%) alloy were investigated. The cold-rolled alloy was annealing heat-treated at different temperatures in the range of 500–900 °C for 30 min. The shape recovery behavior of the alloy was investigated using strip bending test followed by recovery heating. The microstructural evolution and the stress-strain response of the alloy heat-treated at different temperatures revealed that the recovery took place at a heat-treatment temperature higher than 600 °C. Recrystallization occurred when the heat-treatment temperature was higher than 800 °C. Meaningful shape recovery was observed only when the alloy was annealed at temperatures higher than 600 °C. The highest recovery strain of up to 2.56% was achieved with a pre-strain of 5.26% and recovery heating temperature of 400 °C, when the alloy was heat-treated at 700 °C. Conversely, the yield strength reduced significantly with increasing annealing heat-treatment temperature. The experimental observations presented in this paper provide a guideline for post-annealing heat-treatment when a good compromise between mechanical property and shape recovery performance is required.

Highlights

IntroductionNumerous studies have been conducted to use the alloys in structural applications due to their high elastic stiffness; strength; and, most importantly, low raw material cost
In the OM images, the γ-phases appear in brown, the ε-phases appear in white, and the α’-(body-centered tetragonal) phases appear in dark blue, [7]
Shear bands were clearly seen in the microstructure, which were tilted by approximately 45 degrees to the rolling direction (RD)

Summary

Introduction

Numerous studies have been conducted to use the alloys in structural applications due to their high elastic stiffness; strength; and, most importantly, low raw material cost. One possible application of the alloys could be the use of their high recovery-induced stress. By restraining the shape recovery, a so-called recovery stress can be generated in the material, resulting in pre-stressing or clamping forces [2]. Such behavior can be used in pipe joints, rail couplings, or pre-stressing reinforcement of civil structures [3,4,5,6,7,8,9,10]. It has been shown that Fe-SMA has good fatigue [12]

Methods

Results

Conclusion