Deformation and its Structure in Llo Ti-Al-Nb Compound Alloys

ABSTRACTThe ternary TiAl-Nb (Llo) alloys stabilized at 1000°C for a week were prepared into miniature specimens for compressive deformation tests. The specimens were deformed in uniaxial compression at room temperature as well as various high temperatures. The yield stress and fracture strain were determined with respect to Nb concentration, and as a function of temperature to investigate positive temperature dependence.Dislocation structures and other deformation structures of the deformed alloys were studied by TEM.

Download Full-text

Plastic Deformations in Single Crystals of FePd with the L10 Structure

MRS Proceedings ◽

10.1557/proc-1128-u09-07 ◽

2008 ◽

Vol 1128 ◽

Author(s):

Katsushi Tanaka ◽

Wang Chen ◽

Kyosuke Kishida ◽

Norihiko L. Okamoto ◽

Haruyuki Inui

Keyword(s):

Plastic Deformation ◽

Shear Stress ◽

Temperature Dependence ◽

Single Crystals ◽

Yield Stress ◽

Room Temperature ◽

Positive Temperature ◽

Plastic Deformations ◽

L10 Structure ◽

Critical Resolved Shear Stress

AbstractCompressive deformations of L10-ordered single crystals of FePd have been investigated from room temperature to 873 K. The critical resolved shear stress for superlattice dislocations is hard to determine resulting from buckling that occurs after a small amount of conventional plastic deformation. The CRSS for superlattice dislocations determined from yield stress is significantly larger than that of ordinary dislocations. The CRSS for octahedral glide of ordinary and superlattice dislocations are virtually independent of the temperature, and the positive temperature dependence of the yield stress is not observed for both, ordinary and superlattice dislocations, by the present experiments.

Download Full-text

Effects of Alloying Elements on the Temperature Dependence of Yield Stress in L12-Co3(Al,W)

MRS Proceedings ◽

10.1557/opl.2015.161 ◽

2015 ◽

Vol 1760 ◽

Author(s):

Zhenghao M. T. Chin ◽

Norihiko L. Okamoto ◽

Haruyuki Inui

Keyword(s):

High Temperature ◽

Temperature Dependence ◽

Yield Stress ◽

Room Temperature ◽

Single Phase ◽

Alloying Elements ◽

High Temperature Strength ◽

Positive Temperature ◽

Compression Tests ◽

Polycrystalline Alloys

ABSTRACTThe effects of alloying elements (Ni/Ta) on the temperature dependence of yield stress in Co3(Al,W) with the L12 structure have been investigated through compression tests of nearly single-phase polycrystalline alloys in the temperature range between room temperature to 1,473K. Compared with a ternary Co3(Al,W), a Ni/Ta-added Co3(Al,W) alloy exhibits a higher γ΄ solvus temperature and lower onset temperature of the yield stress anomaly (positive temperature dependence of yield stress), suggesting that the CSF energy is increased by Ni/Ta addition. As a consequence, the high-temperature strength in Co3(Al,W) is considerably enhanced.

Download Full-text

Effect of Vanadium on Plastic Deformation in Llo TiAl Compound Alloys

MRS Proceedings ◽

10.1557/proc-133-687 ◽

1988 ◽

Vol 133 ◽

Cited By ~ 6

Author(s):

Sung H. Whang ◽

Yoo-Dong Hahn

Keyword(s):

Plastic Deformation ◽

Yield Stress ◽

Uniaxial Compression ◽

Fracture Stress ◽

Room Temperature ◽

Stacking Faults ◽

Aluminum Concentration ◽

Stress And Strain ◽

Thin Foils ◽

Miniature Specimens

ABSTRACTTernary Ti-Al-V (Llo) alloys containing vanadium up to 10 at.% and aluminum in the range of 50–55 at.% were prepared. Miniature specimens machined from these alloys were deformed in uniaxial compression at room temperature.The yield stress, and fracture stress and strain were determined with respect to vanadium and aluminum concentration. The deformed alloys were electropolished into thin foils and studied by TEM. In particular, the types of dislocations, stacking faults and twins in the Ti-Al-V alloys were investigated by TEM.

Download Full-text

Strain Rate Dependence of the Flow Stress and Work-Hardening of Single Crystals of NI3(Al,Hf)B

MRS Proceedings ◽

10.1557/proc-364-695 ◽

1994 ◽

Vol 364 ◽

Author(s):

S. S. Ezz ◽

Y. Q. Sun ◽

P. B. Hirsch

Keyword(s):

Flow Stress ◽

Strain Rate ◽

Temperature Dependence ◽

Single Crystals ◽

Yield Stress ◽

Strain Rate Sensitivity ◽

Work Hardening ◽

Room Temperature ◽

Rate Sensitivity ◽

Controlling Mechanism

AbstractThe strain rate sensitivity ß of the flow stress τ is associated with workhardening and β=(δτ/δln ε) is proportional to the workhardening increment τh = τ - τy, where τy is the strain rate independent yield stress. The temperature dependence of β/τh reflects changes in the rate controlling mechanism. At intermediate and high temperatures, the hardening correlates with the density of [101] dislocations on (010). The nature of the local obstacles at room temperature is not established.

Download Full-text

Plastic Deformations in L10-Ordered Single Crystals with their c/a Ratios Less than Unity

Materials Science Forum ◽

10.4028/www.scientific.net/msf.561-565.459 ◽

2007 ◽

Vol 561-565 ◽

pp. 459-462

Author(s):

Katsushi Tanaka ◽

Hiromitsu Ide ◽

Yoshinori Sumi ◽

Kyosuke Kishida ◽

Haruyuki Inui

Keyword(s):

Shear Stress ◽

Temperature Dependence ◽

Single Crystals ◽

Room Temperature ◽

The Other ◽

Compressive Deformation ◽

Positive Temperature ◽

Plastic Deformations ◽

Temperature Range ◽

Critical Resolved Shear Stress

Compressive deformation of L10-ordered single crystals of FePd whose c/a ratio less than unity have been investigated from room temperature to 823 K. The results show that the critical resolved shear stress (CRSS) for octahedral glide of ordinary dislocations is smaller than that of super-lattice dislocations in all the temperature range investigated, that is the opposite sense to the case of Ti-56 mol% Al. The CRSS for ordinary dislocations virtually independent to the temperature. On the other hand, the CRSS for super dislocations exhibits a weak positive temperature dependence from room temperature up to 573 K and decreases in higher temperatures.

Download Full-text

The Temperature Dependence of Yield Stress and Fracture Toughness in Unstabilized Zirconia Crystals

MRS Proceedings ◽

10.1557/proc-78-89 ◽

1986 ◽

Vol 78 ◽

Cited By ~ 1

Author(s):

T. W. Coyle ◽

R. P. Ingel ◽

P. A. Willging

Keyword(s):

Fracture Toughness ◽

Flexural Strength ◽

Temperature Dependence ◽

Yield Stress ◽

Test Temperature ◽

Room Temperature ◽

Single Edge ◽

Melting Technique ◽

Strength Tests ◽

Edge Notch

ABSTRACTThe flexural strength and the single edge notch beam fracture toughness of undoped ZrO2 crystals, grown by the skull melting technique, were examined from room temperature to 1400°C. On heating the toughness increased with test temperature to a maximum of 4.0 MPajm at 1225°C then gradually decreased to 2.6 MPa/m. Upon cooling after a 20 minute hold at 1250°C an increase in toughness to 5 MPa/m was observed at 1200°C; upon cooling to lower temperatures Kic gradually diminished. The loaddeflection curves for the flexural strength tests showed marked nonlinearity before failure for samples tested on cooling. The temperature dependence of the apparent yield stress suggests that initial yielding occurs by slip above 1200°C but that from 1200°C to 1050°C the observed yielding is due to stress induced tetragonal to monoclinic transformation.

Download Full-text

Yield Stress Anomaly for 1/2〈112] {1111} Slip in y-Titanium Aluminide

MRS Proceedings ◽

10.1557/proc-552-kk1.9.1 ◽

1998 ◽

Vol 552 ◽

Author(s):

S. Jiao ◽

N. Bird ◽

P. B. ◽

G. Taylor

Keyword(s):

Yield Stress ◽

High Temperatures ◽

Titanium Aluminide ◽

Room Temperature ◽

Elastic Strain Energy ◽

Weak Beam ◽

Transmission Electron ◽

Different Temperatures ◽

Edge Dislocations ◽

Dislocation Dissociation

ABSTRACTTransmission electron microscopy (TEM) studies of dislocation structures in single crystals of TiAl containing 54.5 or 54.7 at% Al deformed at different temperatures revealed the occurrence of slip on ½〈112]{ {111} at room temperature and near the peak of the yield stress anomaly (YSA). Measurements of the corresponding yield stresses revealed the existence of a YSA for this type of slip. Weak-beam TEM showed the presence of locks at room temperature for 30° dislocations and at high temperatures for edge dislocations. Both types of locks involve dissociation on two intersecting { 1111} type planes, driven by reduction in elastic strain energy. The edge dislocation dissociation at high temperatures involves both climb and glide.

Download Full-text