Microstructural Evolution and Functional Properties of Fe-Mn-Al-Ni Shape Memory Alloy Processed by Selective Laser Melti
- PDF / 1,264,720 Bytes
- 5 Pages / 593.972 x 792 pts Page_size
- 24 Downloads / 224 Views
es, shape memory alloys (SMAs) have been the focus of intensive research.[1,2] Based on a fully reversible solid-to-solid phase transformation involving a high-temperature austenitic parent phase and a low-temperature martensitic product phase, unique properties can be obtained. Numerous alloys have been proposed and studied in the past, nickel-titanium (Ni-Ti) and its ternary and quaternary derivatives being the most
THOMAS NIENDORF, Professor, is with the Institut fu¨r Werkstofftechnik, Universita¨t Kassel, 34125 Kassel, Germany. FLORIAN BRENNE, Research Assistant, is with the Lehrstuhl fu¨r Werkstoffkunde, Universita¨t Paderborn, 33098 Paderborn, Germany. PHILIPP KROOß and MALTE VOLLMER, formerly Research Assistants with the Institut fu¨r Werkstofftechnik, TU Bergakademie Freiberg, 09599 Freiberg, Germany, are now Research Assistants with the Institut fu¨r Werkstofftechnik, Universita¨t Kassel. Contact email: krooss@ uni-kassel.de JOHANNES GU¨NTHER, Research Assistant, and HORST BIERMANN, Professor, are with the Institut fu¨r Werkstofftechnik, TU Bergakademie Freiberg. DIETER SCHWARZE, Process Engineer, is with SLM Solutions GmbH, 23556 Lu¨beck, Germany. Manuscript submitted October 28, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS A
researched systems.[1–4] As Ni-Ti SMAs suffer high production cost, alternative SMAs composed of cheaper alloying elements were developed. Copper-based alloys are well characterized, but unfortunately suffer rapid martensitic stabilization, poor ductility, and thus limited formability.[5,6] Work conducted in the group of Kainuma clearly revealed that alloy composition as well as microstructural control by thermomechanical treatment allows for better formability.[7] Shape memory properties as well can be significantly improved by thermomechanical processing and cyclic heat treatment, respectively. The key to superior shape memory performance in Cu-based alloys is the existence of microstructures characterized by a very low degree of constraints.[8] Omori et al.[9] proposed cyclic heat treatment in order to establish bamboo-like, i.e., oligocrystalline, microstructures. A different approach was chosen by Liu et al.,[10] who used continuous unidirectional casting in order to obtain strongly textured Cu-based SMAs featuring columnar grains with a mean column diameter of about 1 mm. Associated grain boundaries mainly were of low-angle character, i.e., low-energy boundaries.[10] Obviously, both microstructures differ significantly; however, due to the low degree of constraints, shape memory performance, i.e., maximum attainable pseudo-elastic strains and reversibility, in either case was similar to that in the single crystalline material.[8–10] In line with the findings obtained in the Cu-based systems, iron-based SMAs show a strong interrelationship of shape memory properties and microstructure.[11–13] Mechanical constraints imposed by fine-grained microstructures characterized by a high grain boundary to sample volume ratio and the presence of triple points result in poor pseudo-elastic response an
Data Loading...
