Additive Manufacturing of Co-Ni-Ga High-Temperature Shape Memory Alloy: Processability and Phase Transformation Behavior
- PDF / 1,087,298 Bytes
- 6 Pages / 593.972 x 792 pts Page_size
- 14 Downloads / 186 Views
-Ti is currently the shape memory alloy (SMA) system of choice in many niche applications due to its good biocompatibility, high transformation strains and excellent cyclic stability. However, Ni-Ti SMAs suffer from limited transformation temperatures (TTs) and high production costs.[1–3] To extend the application temperature range, high-temperature (HT-) SMAs featuring increased martensite start temperatures (Ms) have
C. LAUHOFF, A. FISCHER, A. LIEHR, P. KROOß, J. RICHTER, M. KAHLERT, and T. NIENDORF are with the Institute of Materials Engineering, University of Kassel, 34125 Kassel, Germany. Contact e-mail: lauhoff@uni-kassel.de C. SOBRERO is with the Institute of Physics Rosario (CONICET), Rosario’s National University, 2000 Rosario, Argentina. F. BRENNE is with the Institute of Materials Engineering, University of Kassel and also with the Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801. S. BO¨HM is with the Institute of Production Technologies and Logistics, University of Kassel, 34125 Kassel, Germany. Manuscript submitted August 14, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS A
been designed. These alloys enable new applications in the fields of aerospace, automotive, oil and gas as well as other industries.[4,5] Adding a third element to Ni-Ti is a common practice to increase the TTs.[4] Ni-Ti-Hf is currently the most promising HT-SMA being in focus of many studies.[6–8] However, high costs of the alloying elements as well as highly challenging processing and machining remain major roadblocks towards widespread use of Ni-Ti-Hf in industrial applications.[9,10] Over the last decades, many alternative alloy systems have been introduced as HT-SMA candidates.[4,5] Among the alternative systems, the Heusler-type Co-Ni-Ga alloys have gained considerable attention[11]: Co-Ni-Ga, undergoing a martensitic transformation from cubic B2-ordered austenite to tetragonal L10 martensite,[12] consists of relatively inexpensive alloying elements and features excellent functional properties at elevated temperatures. In single-crystalline state, a fully reversible pseudoelastic response up to temperatures of about 500 °C and excellent functional stability at temperatures up to 100 °C have been shown.[13–15] This qualifies Co-Ni-Ga for high-temperature damping applications. Aging of stress-induced martensite, referred to as SIM-aging,[16] changes the chemical order and, thus, is suited to directly tailor the TTs. Hence, stable hightemperature actuation can be realized as well.[16,17] In addition, good formability can be obtained by controlled segregation of the ductile secondary c-phase (A1).[18–21] The fundamental properties of this alloy system are characterized in depth. However, excellent functional properties have been reported mainly for single-crystalline material so far. Owing to a pronounced anisotropic transformation behavior and a limited number of martensite variants, deformation constraints at grain boundaries (GB) cannot be sufficiently accommodated in pol
Data Loading...
