Microstructure, phase stability, mechanical properties, and shape memory characteristics of Ni-Fe-Al-B alloys
- Oak Ridge National Lab., TN (United States)
- Johnson Controls, Inc., Milwaukee, WI (United States)
- Eaton Corp., Milwaukee, WI (United States)
Conventionally cast and hot-rolled Ni-Fe-Al-B alloys containing 4--20 at.% Fe, 23.9--31.5 at.% Al, and 300 wppm B were investigated in this study. After oil quenching from 1300 C, all the alloys -- except SMA-15 (27Al-14Fe) -- have a two-phase microstructure, one phase of which is martensite with the characteristic platelet morphology, and the other a globular second phase distributed throughout the microstructure. The amount of second phase generally increases with increasing Fe content. Alloys containing less than 145 Fe were found to be quite brittle at room temperature, indicating that the second phase is at least partly responsible for room-temperature ductility. The best tensile ductility (12%) was obtained in SMA-17 (23.9Al-20Fe) which was shown by X-ray diffraction to consist of 70% (mostly disordered) fcc [(Ni,Fe){sub 3}(Al,Fe)] + 25% (partly ordered) bct (martensite) + 5% B2 (NiAl). Differential scanning calorimetry showed that the transformation temperatures for this alloy were M{sub p} = 65{degrees}C and A{sub p} = 95{degrees}C. Room-temperature tensile strains of 2--3% could be almost completely recovered in SMA-17 by heating for 3 min. at 600{degrees}C with the load removed. Upon subsequent cycling (i.e., strain-anneal cycling), the amount of strain recovery increased dramatically from 70% in the first cycle to nearly 100% after 4--5 cycles, indicating that cold work may help in improving the shape memory characteristics of this alloy. SMA-15 was found to have significantly higher transformation temperatures (M{sub p} = 143{degrees}C and A{sub p} = 170{degrees}C) than SMA-17; however, it is relatively brittle compared to SMA-17.
- Research Organization:
- Oak Ridge National Lab., TN (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 10124625
- Report Number(s):
- CONF-911202-62; ON: DE92008276
- Resource Relation:
- Conference: Annual fall meeting of the Materials Research Society (MRS),Boston, MA (United States),2-6 Dec 1991; Other Information: PBD: [1991]
- Country of Publication:
- United States
- Language:
- English
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