Intrinsic ductility and environmental embrittlement of binary Ni[sub 3]Al

Journal Article · Thu Apr 01 04:00:00 EST 1993 · Scripta Metallurgica et Materialia; (United States)

DOI:https://doi.org/10.1016/0956-716X(93)90366-Z· OSTI ID:6520745

George, E P; Liu, C T ^[1]; Pope, D P ^[2]

---

1. Oak Ridge National Lab., TN (United States)
2. Univ. of Pennsylvania, Philadelphia (United States)

Polycrystalline, B-free Ni[sub 3]Al (23.4 at.% Al), produced by cold working and recrystallizing a <100> single crystal, exhibits room temperature tensile ductilities of 3-5% in air and 13-16% in oxygen. These ductilities are considerably higher than anything previously reported, and demonstrate that the intrinsic' ductility of Ni[sub 3]Al is much higher than previously thought. They also show that the moisture present in ordinary ambient air can severely embrittle Ni[sub 3]Al (ductility decreasing from a high of 16% in oxygen to a low of 3% in air). Fracture is predominantly intergranular in both air and oxygen. This indicates that, while moisture can further embrittle the GBs in Ni[sub 3]Al, they persist as weak links even in the absence of environmental embrittlement. However, they are not intrinsically brittle' as once thought, since they can withstand relatively large plastic deformations prior to fracture. Because B essentially eliminates environmental embrittlement in Ni[sub 3]Al - and environmental embrittlement is a major cause of poor ductility in B-free Ni[sub 3]Al - it is concluded that a significant portion of the so-called B effect must be related to suppression of moisture-induced environmental embrittlement. However, since B-doped Ni[sub 3]Al fractures transgranularly, whereas B-free Ni[sub 3]Al fractures predominantly intergranularly, B must have the added effect that it strengthens the GBs. A comparison with the earlier work on Zr-doped Ni[sub 3]Al shows that Zr improves the ductility of Ni[sub 3]Al, both in air and (and even more dramatically) in oxygen. While the exact mechanism of this ductility improvement is not clear at present, Zr appears to have more of an effect on (enhancing) GB strength than on (suppressing) environmental embrittlement.

• DOE Contract Number: AC05-84OR21400
• OSTI ID: 6520745
• Journal Information: Scripta Metallurgica et Materialia; (United States), Journal Name: Scripta Metallurgica et Materialia; (United States) Vol. 28:7; ISSN SCRMEX; ISSN 0956-716X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103* -- Metals &amp; Alloys-- Mechanical Properties
ALLOYS
ALUMINIUM ALLOYS
BORON
BORON ADDITIONS
BORON ALLOYS
COMPARATIVE EVALUATIONS
DATA
DUCTILITY
ELEMENTS
EMBRITTLEMENT
EVALUATION
EXPERIMENTAL DATA
FRACTURE PROPERTIES
INFORMATION
MECHANICAL PROPERTIES
METALLURGICAL EFFECTS
METALS
NICKEL ALLOYS
NICKEL BASE ALLOYS
NUMERICAL DATA
SEMIMETALS
TENSILE PROPERTIES
TRANSITION ELEMENTS
ZIRCONIUM
ZIRCONIUM ADDITIONS
ZIRCONIUM ALLOYS