Investigation on the effect of strain value in high pressure torsion process on the microstructure, mechanical properties an‎d shape memory behavior of Fe-15Mn-5Si-7Cr-5Ni alloy

10/20/2025 12:00:00 AM

In recent years, iron-based shape memory alloys have been used significantly in commercial an‎d engineering applications, because these alloys have many advantages such as low cost, good workability an‎d high strength. The shape memory property in these alloys arises from the transformation of FCC austenite to HCP martensite under deformation, an‎d its reverse transformation upon heating. In addition, Fe-Mn-Si-based shape memory alloys also exhibit the unique property of pseudoelasticity. However, Ni-Ti-based shape memory alloys have better shape memory. but due to the high cost of these alloys, their application has been limited. Therefore, researchers have always been looking for ways to improve the shape memory property of iron-based alloys. One of the most common methods for enhancing shape memory in these alloys is the application of severe plastic deformation processes. In this study, the effect of high-pressure torsion on the microstructure, mechanical properties, pseudoelastic behavior an‎d shape memory behavior of an iron-based shape memory alloy with the chemical composition Fe-15Mn-5Si-7Cr-5Ni (wt%) was investigated. Results showed that this alloy contained two phases, austenite an‎d epsilon martensite, an‎d after applying high-pressure torsion, martensite fraction was increased. The tensile test showed that the ultimate strength of the solution annealed sample was 876 MPa, which increased to 904 MPa after only 0.5 turns of high-pressure torsion, an‎d its maximum value was 1670 MPa after 3 turns. Microhardness testing also indicated that the hardness value increased an‎d became more uniform throughout the disk with an increase in the number of HPT turns up to 10 turns, an‎d the highest hardness value was reached at the edges of the disk, about 612 Vickers. Examination of the fracture surfaces of the samples also showed that with an increase in the number of high-pressure torsion turns up to 10 turns, areas with a more brittle fracture surface were observed. due to the pseudoelastic results, hysteresis was observed in all samples an‎d increasing strain, led to an increase in the hysteresis width. Also, the highest shape recovery rate was achieved for the 3-turn sample, at a pre-strain of 1%, for 66%. The highest percentage of recovery strain was also achieved in the same sample, at 3.1%.

آلياژ حافظه‌دار پايه Fe-Mn-Si , فرايند پيچش تحت فشار بالا , ريزساختار , خواص مكانيكي , رفتار حافظه‌داري

Shape memory alloys , Iron based shape memory alloys , Severe plastic deformation , High pressure torsion , Shape memory effect

Mozhdeh Jamshidi Savadroodbari

Dr.Hamidreza koohdar