Ductility and Fracture Behavior of Polycrystalline Ni3Al Alloys

1986 ◽  
Vol 81 ◽  
Author(s):  
C. T. Liu
Keyword(s):  
Fracture Behavior ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Grain Shape ◽  
Tensile Ductility ◽  
Dynamic Effect ◽  
Al Alloys ◽  
Gaseous Oxygen ◽  
Comprehensive Review ◽  
Room Temperature Ductility

AbstractThis paper provides a comprehensive review of the recent work on tensile ductility and fracture behavior of Ni3AI alloys tested at ambient and elevated temperatures. Polycrystalline Ni3Al is intrinsically brittle along grain boundaries, and the brittleness has been attributed to the large difference in valency, electronegativity, and atom size between nickel and aluminum atoms. Alloying with B, Mn, Fe, and Be significantly increases the ductility and reduces the propensity for intergranular fracture in Ni3 Al alloys. Boron is found to be most effective in improving room-temperature ductility of Ni3Al with <24.5 at. % Al.The tensile ductility of Ni3Al alloys depends strongly on test environments at elevated temperatures, with much lower ductilities observed in air than in vacuum. The loss in ductility is accompanied by a change in fracture mode from transgranular to intergranular. This embrittlement is due to a dynamic effect involving simultaneously high localized stress, elevated temperature, and gaseous oxygen. The embrittlement can be alleviated by control of grain shape or alloying with chromium additions. All the results are discussed in terms of localized stress concentration and grain-boundary cohesive strength.

Effect of chromium on properties of Fe3Al

1989 ◽  
Vol 4 (5) ◽  
pp. 1156-1163 ◽  
Author(s):  
C. G. McKamey ◽  
J. A. Horton ◽  
C. T. Liu
Keyword(s):  
Tensile Strength ◽  
Fracture Mode ◽  
Mixed Mode ◽  
Fracture Behavior ◽  
Room Temperature ◽  
Antiphase Boundary ◽  
Transgranular Cleavage ◽  
Room Temperature Ductility ◽  
Wavy Slip ◽  
Strength And Ductility

The effects of the addition of chromium on several properties of Fe3Al, including tensile strength and ductility, fracture behavior, and slip and dislocation characteristics, were studied. Alloying with up to 6 at. % chromium results in an increase in room temperature ductility from approximately 4% to 8–10%. Along with this increase in ductility, the addition of chromium produces a change in fracture mode from transgranular cleavage to a mixed mode of intergranular-transgranular cleavage, and a change in slip behavior from coarse straight slip to fine wavy slip. These phenomena are discussed in terms of the effect of chromium on the antiphase boundary energies and dislocation characteristics.

Electron microscope studies of climb of dissociated dislocations

1978 ◽  
Vol 36 (1) ◽  
pp. 324-325
Author(s):  
C.B. Carter ◽  
D. Cherns ◽  
P.B. Hirsch ◽  
H. Saka
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Point Defects ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Al Alloys ◽  
Weak Beam ◽  
High Supersaturation ◽  
Beam Technique

The mechanism of climb of dissociated dislocations in f.c.c. metals and alloys is not well understood. Climb of dislocations by absorption or emission of vacancies at existing jogs in dissociated dislocations has been observed using the “weak-beam” technique of electron microscopy, but the mechanism of nucleation of jogs is not clear. In this paper we report some results of experiments designed to study the nucleation problem, and more generally the mechanism of absorption of point defects under conditions of high supersaturation.Thin (111) sections of deformed single crystals of Cu-Al alloys, of various compositions, have been electron irradiated in an AEI EM7 HVEM up to 1 MeV, either at room temperature, or elevated temperatures up to 200°C, using a goniometer heating stage. Observations under weak beam conditions have been made a) in situ in the HVEM b) at 100kV in an JEM100B, following irradiation in the HVEM. Interstitials produced by the irradiation are expected to be preferentially attracted to the dislocations because of the strong dislocation-interstitial interaction.

On the Mechanisms of Ductility Enhancement in β+γ′- Ni70Al30 and β+(γ+γ)-Ni50Fe30Al20In Situ Composites

1992 ◽  
Vol 273 ◽  
Author(s):  
A. Misra ◽  
R. D. Noebe ◽  
R. Gibala
Keyword(s):  
Room Temperature ◽  
Volume Fraction ◽  
Tensile Ductility ◽  
Nominal Composition ◽  
Substantial Portion ◽  
Directionally Solidified ◽  
Ductile Phase ◽  
Room Temperature Ductility ◽  
Slip Transfer ◽  
Slip Traces

ABSTRACTDuctile phase reinforcement is an attractive approach for improving room temperature ductility and toughness of intermetallics. Two alloys of nominal composition (at.%) Ni70Al30 and Ni50Fe30Al20 were directionally solidified to produce quasi-lamellar microstructures. Both alloys exhibit ∼10% tensile ductility at 300 K when the ductile phase is continuous, while the Ni70Al30 alloy has a tensile ductility of ∼4% when the γ′ phase is discontinuous. Observations of slip traces and dislocation substructures indicate that a substantial portion of the ductility enhancement is a result of slip transfer from the ductile phase to the brittle matrix. The details of slip transfer in the two model materials and the effect of the volume fraction and morphology of the ductile phase on the ductility enhancement in the composite are discussed.

Effect of Bi Addition on Thermal Stability and Tensile Ductility of Mg-3%Zn-0.4%Zr Alloy

2010 ◽  
Vol 654-656 ◽  
pp. 647-650
Author(s):  
Joong Hwan Jun ◽  
Min Ha Lee
Keyword(s):  
Thermal Stability ◽  
Tensile Strength ◽  
Elevated Temperature ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Tensile Ductility ◽  
Grain Structure ◽  
Hot Rolled ◽  
Thermal Stability Of ◽  
Zr Alloy

Thermal stability of  grains and tensile ductilities at room and elevated temperatures were investigated and compared for Mg-3%Zn-0.4%Zr and Mg-3%Zn-0.4%Zr-1%Bi alloys in hot-rolled state. The Bi-added alloy showed slightly finer-grained microstructure with enhanced thermal stability, which is closely associated with fine Mg-Bi compounds acting as obstacles for the migration of grain boundaries. The Mg-3%Zn-0.4%Zr-1%Bi alloy exhibited better tensile strength at room temperature and tensile ductilities at elevated temperature. Finer and more homogeneous grain structure with higher thermal stability would be responsible for the enhanced tensile properties in the Bi-added alloy.

Fracture Behavior of Micro-Sized Specimens Prepared From an Amorphous Alloy Thin Film at Ambient and Elevated Temperatures

2001 ◽  
Vol 695 ◽  
Author(s):  
K. Takashima ◽  
R. Tarumi ◽  
Y. Higo
Keyword(s):  
Thin Film ◽  
Fracture Toughness ◽  
Amorphous Alloy ◽  
Cantilever Beam ◽  
Fracture Behavior ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Alloy Thin Film ◽  
Type Specimens ◽  
Beam Type

ABSTRACTFracture behavior of micro-sized cantilever beam type specimens prepared from an electroless deposited Ni-P amorphous alloy thin film has been investigated at ambient and elevated temperatures. Cantilever beam type specimens with dimensions of 10 x 12 x 50 μm3 were prepared from an electroless deposited Ni-P amorphous alloy thin film and notches were introduced by focused ion beam machining. Fatigue pre-cracks were introduced ahead of the notches. The introduction of fatigue pre-crack and fracture toughness tests were carried out using a mechanical testing machine for micro-sized specimens. The temperature of the specimen was controlled from room temperature to 473 K using a newly developed heating system. Compared with room temperature, fracture toughness increased approximately 40 % at 373 K but decreased 19 % at 473 K. The increase of fracture toughness at 373 K is considered to be related with the formation of nano-sized crystals and the decrease of fracture toughness at 473 K is considered to be due to the growth of crystals. It is required to consider the fracture behavior obtained in this investigation when designing actual MEMS devices using electroless deposited amorphous films.

scholarly journals The Mechanical Properties of FeAl

1998 ◽  
Vol 552 ◽  
Author(s):  
I. Baker ◽  
E. P. George
Keyword(s):  
Mechanical Properties ◽  
Water Vapor ◽  
High Temperature ◽  
Low Temperature ◽  
Yield Strength ◽  
Fracture Behavior ◽  
Room Temperature ◽  
Room Temperature Ductility ◽  
Equilibrium Vacancy ◽  
Made In

ABSTRACTIn the last few years, considerable progress been made in obtaining reproducible mechanical properties data for binary FeAl alloys. Two sets of observations are the foundation of this progress. The first is that the large equilibrium vacancy concentrations that exist in FeAl at high temperature are easily retained during cooling, and that these strongly affect the low-temperature mechanical properties. The second is that room-temperature ductility is adversely affected by water vapor. The purpose of this paper is to highlight our understanding of key phenomena and to show how an understanding of the factors which control the yield strength and fracture behavior has followed from the discovery of the above two effects.

Room Temperature Ductility of B2-Type CoZr Intermetallic Compounds

2006 ◽  
Vol 980 ◽  
Author(s):  
Yasuyuki Kaneno ◽  
Takayuki Takasugi ◽  
Mitsuhiko Yoshida ◽  
Hiroshi Tsuda
Keyword(s):  
Room Temperature ◽  
Elevated Temperatures ◽  
Volume Fraction ◽  
Tensile Ductility ◽  
Tensile Tests ◽  
Ductile Deformation ◽  
Chemical Compositions ◽  
Second Phase ◽  
Intermetallic Alloys ◽  
Hot Rolled

AbstractB2 (CsCl) CoZr intermetallic alloys with different chemical compositions were hot-rolled and subsequently recrystallized to evaluate tensile properties and rolling workability. Co-49.0Zr, -49.5Zr and -50.0Zr alloys showed the B2-matrixed microstructure containing C15 Co2Zr dispersions, while Co-50.5Zr and -51.0Zr alloys showed the B2-matrixed microstructure containing C16 CoZr2 dispersions. These homogenized ingots were successfully hot-rolled without edge cracks, except for the Co-51.0Zr alloy. The tensile tests revealed that the Co-49.5Zr, -50.0Zr and -50.5Zr alloys exhibited a notable tensile ductility at room temperature as well as at elevated temperatures. Moreover, the recrystallized CoZr alloys were cold-rolled up to 70% reduction without intermediate annealing. It was also found that tensile ductility was most prominent in the Co-50.0Zr alloy with the least volume fraction of second phase dispersions in the investigated alloys, suggesting that the B2 phase of CoZr was inherently ductile. Deformation microstructures were characterized by means of XRD and TEM observations. Mechanisms responsible for the observed large tensile ductility of the CoZr alloys were discussed, on the basis of the observed deformation microstructures.

The Work Hardening of some Commercial Al Alloys

2006 ◽  
Vol 519-521 ◽  
pp. 55-62 ◽  
Author(s):  
David J. Lloyd
Keyword(s):  
Elevated Temperature ◽  
Work Hardening ◽  
Deformation Behavior ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Al Alloys ◽  
Temperature Behavior ◽  
Physical Metallurgy

The work hardening of Al alloys is very important in regards to their formability and their deformation behavior in service. The majority of the work in the literature has considered relatively pure materials, and has tended to concentrate on room temperature and elevated temperature behavior. In Al alloys there is interest in work hardening at lower temperatures since they are quite restricted in terms of the elevated temperatures at which they can be used. In this paper the work hardening of commercial 1000, 3000 and 5000 alloys have been investigated from room temperature down to 85°K. The work hardening has been analyzed using the Voce approach, and it is shown that this enables the work hardening of the different alloys to be related to their basic physical metallurgy.

Ductility Improvement of Direct-Cast Gamma TiAl-Based Alloy Sheet

1996 ◽  
Vol 460 ◽  
Author(s):  
Toshihiro Hanamura ◽  
Keizo Hashimoto
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
Tensile Ductility ◽  
Particle Dispersion ◽  
Alloy Sheet ◽  
High Temperature Strength ◽  
High Oxygen Content ◽  
Room Temperature Ductility ◽  
Average Grain Size ◽  
The Matrix

ABSTRACTFor improving the room temperature tensile ductility of direct-cast gamma TiAl sheets without affecting their high-temperature strength, direct sheet casting with T1B2 particle dispersion is employed and conducted. The T1B2 addition and rapid cooling results in the formation of a fine equiaxed grain microstructure with an average grain size of ∼10μm, contributing to the increase in the room temperature ductility to 2.1% with the high-temperature tensile strength kept at about 200MPa. This improvement of room-temperature ductility is attributable to the following fact. The high oxygen content of this material, about 2500wt. ppm, is not harmful to the tensile ductility when the oxygen is in the solid solution of the 0:2 lamellar phase or in oxide particles, which are fine enough not to cause brittleness to the matrix. From these findings, a principle is proposed that oxygen is not harmful to the ductility of gamma TiAl when its microstructure containing oxygen is fine enough.

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