Characterization, processing, and alloy design of NiAl-based shape memory alloys
- Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.
- Johnson Controls Inc., Milwaukee, WI (United States)
- Eaton Corp., Milwaukee, WI (United States)
The microstructures and phase transformations in binary Ni-Al, ternary Ni-Al-Fe, and quaternary Ni-Al-Fe-Mn shape memory alloys (SMAs) were investigated by light and electron microscopy, electron and X-ray diffraction, and differential scanning calorimetry. The effects of alloying additions (B, Fe, and Mn) on martensite stability, shape recovery, and tensile ductility were also studied. NiAl-based SMAs can be made ductile by alloying with B for enhanced grain boundary cohesion and Fe for improved bulk properties. Iron has the undesirable effect that it decreases the martensite to austenite transformation temperatures (A[sub p]). Fortunately, A[sub p] can be increased by decreasing the equivalent Al content of the alloy. In this way, a high A[sub p] temperature of [approximately]190 C has been obtained without sacrificing ductility. Recoverable strains of [approximately]0.7% have been obtained in a Ni-Al-Fe alloy with A[sub p] temperature of [approximately]140 C. Manganese additions (2--10%) lower A[sub p], degrade hot workability, and decrease room temperature ductility. Good-quality, ductile SMA ribbons have been produced by melt spinning. However, additional alloy design is required to suppress the aging-induced embrittlement caused by Ni[sub 5]Al[sub 3] formation.
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 7199346
- Journal Information:
- Materials Characterization; (United States), Journal Name: Materials Characterization; (United States) Vol. 32:3; ISSN 1044-5803; ISSN MACHEX
- Country of Publication:
- United States
- Language:
- English
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