Plastic deformation of single crystals with the C11b structure : Effect of the c/a axial ratio

2000 ◽  
Vol 646 ◽  
Author(s):  
Kazuhiro Ito ◽  
Hironori Yoshioka ◽  
Masaharu Yamaguchi
Keyword(s):  
Plastic Deformation ◽  
Single Crystals ◽  
Interplanar Spacing ◽  
Plastic Anisotropy ◽  
Axial Ratio ◽  
Compression Tests ◽  
Key Factors ◽  
Burgers Vector ◽  
Structural Applications ◽  
Very High

ABSTRACTMoSi2 has a great potential for very high temperature structural applications. Plastic deformation of MoSi2 single crystals with the C11b structure is extremely anisotropic. It is caused by non-Schmid behavior of slip on {013}<331> with the higher CRSS values for orientations closer to [001]. In order to provide better understanding of key factors on such non-Schmid behavior in MoSi2 (c/a=2.45), we chose PdZr2 with a c/a axial ratio higher than 3 (c/a=3.30) and characterized the plastic deformation. Compression tests were conducted at various temperatures along [001], [010] and [110] axes. Slip on {013}<100> has the shortest Burgers vector and the largest interplanar spacing in PdZr2 and was observed to be activated for [110] with the lowest CRSS. While slip on {013}<331> can be activated even at -196°C for [001]. Although {013}<331> slip has the same Schmid factors for [001] and [010], the yield stress of the [010]-oriented crystals is about twice higher than that of the [001]-oriented crystals. Thus non-Schmid behavior of slip on {013}<331> is also observed in PdZr2, and the manner is opposite to that in MoSi2. Plastic anisotropy in the C11b structure will be discussed in terms of the c/a axial ratio.

Plastic Deformation of Approximants: Dislocations vs. Phason Lines

1998 ◽  
Vol 553 ◽  
Author(s):  
H. Klein ◽  
M. Feuerbacher ◽  
P. Schall ◽  
K. Urban
Keyword(s):  
Plastic Deformation ◽  
High Temperature ◽  
Single Crystals ◽  
Periodic Lattice ◽  
Length Scale ◽  
Relative Importance ◽  
Line Lattice ◽  
Burgers Vector ◽  
Mechanisms Of Plastic Deformation

AbstractDeformation experiments were performed on single crystals of the ξ-AIPdMn approximant in bending geometry at high temperature. Two different mechanisms of plastic deformation are shown to exist in this phase: one based on dislocations and another novel mechanism based on the motion of phason lines. Burgers vector and line directions of dislocations were determined. Phason lines are shown to build a periodic lattice. The interaction of a dislocation with the phason line lattice results in dislocations on another length scale. This meta-dislocation in the periodic phason line lattice has a Burgers vector of magnitude 165 Å. The relative importance of phason lines and dislocations for the plastic deformation is discussed as a function of the orientation of the sample with respect to the bending geometry.

Physical and Mechanical Properties of Mo5X3+α (X=Si, B, C) Single Crystals

2002 ◽  
Vol 753 ◽  
Author(s):  
Taisuke Hayashi ◽  
Kazuhiro Ito ◽  
Katsushi Tanaka ◽  
Masaharu Yamaguchi
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Single Crystals ◽  
Plastic Anisotropy ◽  
Physical And Mechanical Properties ◽  
Structure Type ◽  
Advanced Materials ◽  
Anisotropy Ratio ◽  
Higher Temperature ◽  
Better Than

ABSTRACTMo5X3+α (X=Si, B, C) intermetallic compounds such as Mo5SiB2 (D8l), Mo5Si3 (D8m) and Mo5Si3C (D88) have a great potential for ultra-high temperature applications. The present study was undertaken putting greater emphasis on clarifying how their physical and mechanical properties are similar or different in terms of a structure type. Some interesting features are summarized in this paper.The resistivity of Mo5SiB2, Mo5Si3 and Mo5Si3C single crystals exhibited a negative curvature (d2ρ(T)/dT2<0), with a tendency towards saturation. In the Mo5Si3C with large ρ0 due to impurity carbon atoms, resistivity saturation is pronounced. In contrast, a much higher temperature is required to reach saturation in the Mo5SiB2. The anisotropy ratio of CTE (αc/αa) for the Mo5SiB2 is about 1.2–1.6 and is significantly reduced from about 2 of the Mo5Si3 and Mo5Si3C. On the other hand, the Young's modulus of the Mo5SiB2 is more anisotropic than those of the Mo5Si3 and Mo5Si3C. Plastic anisotropy was observed in the Mo5SiB2, because only slip on [001] {100} is operative at 1500°C. On the contrary, plastic deformation was observed at temperatures above 1300°C for the Mo5Si3C and Mo5Si3. Anisotropy of their plastic deformation was much less than that of the Mo5SiB2, presumably because more than two slip systems can be activated. Creep resistance of the Mo5SiB2 is much better than that of the Mo5Si3 as well as the most advanced materials such as MoSi2 and Si3N4 based structural ceramics.

Mechanical and thermal properties of single crystals of ZrB2

2002 ◽  
Vol 753 ◽  
Author(s):  
N. L. Oka moto ◽  
M. Kusakari ◽  
K. Tanaka ◽  
H. Inui ◽  
M. Yamaguchi ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Thermal Expansion ◽  
Single Crystals ◽  
Elastic Constants ◽  
Layered Structure ◽  
Mechanical And Thermal Properties ◽  
Slip Systems ◽  
Compression Tests ◽  
Deformation Behaviors ◽  
Temperature Ranges

ABSTRACTCoefficients of thermal expansion (CTE), elastic constants and plastic deformation behaviors of single crystals of ZrB2, which possesses a hexagonal layered structure where pure Zr and pure B atomic planes stack alternatively along the c-axis, have been investigated in wide temperature ranges. While the observed elastic constants indicate highly anisotropic nature of atomic bonding being consistent with the layered structure, the observed CTE values are rather isotropic. Two operative slip systems, (0001)<1120> and on {1100}<1123>, are identified in compression tests. The observed plastic behaviors are discussed in the light of the deduced anisotropy in atomic bonding.

Plastic Deformation of Ni3Nb Single Crystals

1998 ◽  
Vol 552 ◽  
Author(s):  
Kouji Hagihara ◽  
Takayoshi Nakano ◽  
Yukichi Umakoshi
Keyword(s):  
Plastic Deformation ◽  
Shear Stress ◽  
Single Crystals ◽  
Crystal Orientation ◽  
Strengthening Mechanism ◽  
Orientation Dependence ◽  
Slip Model ◽  
Compression Tests ◽  
Increasing Temperature ◽  
Critical Resolved Shear Stress

ABSTRACTTemperature dependence of yield stress and operative slip system in Ni3Nb single crystals with the DOa structure was investigated in comparison with that in an analogous L12 structure. Compression tests were performed at temperatures between 20 °C and 1200 °C for specimens with loading axes perpendicular to (110), (331) and (270).(010)[100] slip was operative for three orientations, while (010)[001] slip for (331) and {211} <10 7 13> twin for (270) orientations were observed, depending on deformation temperature. The critical resolved shear stress (CRSS) for the (010)[100] slip anomaly increased with increasing temperature showing a maximum peak between 400 °C and 800 °C depending on crystal orientation. The CRSS showed orientation dependence and no significant strain rate dependence in the temperature range for anomalous strengthening. The [100] dislocations with a screw character were aligned on the straight when the anomalous strengthening occurred. The anomalous strengthening mechanism for (010)[100] slip in Ni3Nb single crystals is discussed on the basis of a cross slip model which has been widely accepted for some L12-type compounds.

Crystal Structure, Phase Stability and Plastic Deformation Behavior of Ti-rich Ni3(Ti, Nb) Single Crystals with Various Long-Period Ordered Structures.

2004 ◽  
Vol 842 ◽  
Author(s):  
Koji Hagihara ◽  
Tetsunori Tanaka ◽  
Takayoshi Nakano ◽  
Yukichi Umakoshi
Keyword(s):  
Plastic Deformation ◽  
Single Crystals ◽  
Deformation Behavior ◽  
Complex Compounds ◽  
Rhombohedral Structure ◽  
Stacking Sequence ◽  
Compression Tests ◽  
Small Unit ◽  
Long Period ◽  
Plastic Deformation Behavior

ABSTRACTIn Ni-Ti-Nb ternary system, there are some geometrically close-packed (GCP) phases with long-period stacking sequences of a close-packed plane (CPP). Among them, our focus is on the Ni3(Ti0.90Nb0.10) crystals with Pb3Ba-type rhombohedral structure with nine-fold stacking sequence. Compression tests were conducted using the single crystals and the temperature and orientation dependences of plastic deformation behavior were investigated in comparison with those of D024-Ni3Ti crystals with the four-fold stacking sequence. The K-W locking of screw dislocation was found to occur not only in the compounds such as Ni3Al and Ni3Ti with a relatively small unit cell, but also even in complex compounds with longer-period stacking structures by slip on the common CPP in the GCP structures.

Dislocations in alumina deformed by prismatic slip

1978 ◽  
Vol 36 (1) ◽  
pp. 606-607
Author(s):  
J. Cadoz ◽  
J. Castaing ◽  
J. Philibert
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Basal Slip ◽  
Prismatic Slip ◽  
Compression Tests ◽  
Thin Sections ◽  
Burgers Vector ◽  
Maximum Deformation ◽  
Transmission Electron ◽  
Mechanical Thinning

Plastic deformation of alumina has been much studied; basal slip occurs and dislocation structures have been investigated by transmission electron microscopy (T.E.M.) (1). Non basal slip has been observed (2); the prismatic glide system <1010> {1210} has been obtained by compression tests between 1400°C and 1800°C (3). Dislocations with <0110> burgers vector were identified using a 100 kV microscope(4).We describe the dislocation structures after prismatic slip, using high voltage T.E.M. which gives much information.Compression tests were performed at constant strainrate (∿10-4s-1); the maximum deformation reached was 0.03. Thin sections were cut from specimens deformed at 1450°C, either parallel to the glide plane or perpendicular to the glide direction. After mechanical thinning, foils were produced by ion bombardment. Details on experimental techniques can be obtained through reference (3).

Dislocation structures around SiO2 Particles in aged Cu-Cr-SiO2

1978 ◽  
Vol 36 (1) ◽  
pp. 594-595
Author(s):  
N.J. Long ◽  
M.H. Loretto ◽  
C.H. Lloyd
Keyword(s):  
Flow Stress ◽  
Single Crystals ◽  
Room Temperature ◽  
Thin Foil ◽  
Age Hardening ◽  
Dispersion Strengthening ◽  
Accurate Picture ◽  
The Matrix ◽  
Very High ◽  
Good Agreement

IntroductionThere have been several t.e.m. studies (1,2,3,4) of the dislocation arrangements in the matrix and around the particles in dispersion strengthened single crystals deformed in single slip. Good agreement has been obtained in general between the observed structures and the various theories for the flow stress and work hardening of this class of alloy. There has been though some difficulty in obtaining an accurate picture of these arrangements in the case when the obstacles are large (of the order of several 1000's Å). This is due to both the physical loss of dislocations from the thin foil in its preparation and to rearrangement of the structure on unloading and standing at room temperature under the influence of the very high localised stresses in the vicinity of the particles (2,3).This contribution presents part of a study of the Cu-Cr-SiO2 system where age hardening from the Cu-Cr and dispersion strengthening from Cu-Sio2 is combined.

Investigation of shock-wave deformation history from recovered structure

1986 ◽  
Vol 44 ◽  
pp. 434-435
Author(s):  
M.A. Mogilevsky ◽  
L.S. Bushnev
Keyword(s):  
Shock Wave ◽  
Plastic Deformation ◽  
Dislocation Density ◽  
Shock Waves ◽  
Shock Front ◽  
Single Crystals ◽  
Residual Deformation ◽  
Deformation Structure ◽  
Deformation History ◽  
Deformation Velocity

Single crystals of Al were loaded by 15 to 40 GPa shock waves at 77 K with a pulse duration of 1.0 to 0.5 μs and a residual deformation of ∼1%. The analysis of deformation structure peculiarities allows the deformation history to be re-established.After a 20 to 40 GPa loading the dislocation density in the recovered samples was about 1010 cm-2. By measuring the thickness of the 40 GPa shock front in Al, a plastic deformation velocity of 1.07 x 108 s-1 is obtained, from where the moving dislocation density at the front is 7 x 1010 cm-2. A very small part of dislocations moves during the whole time of compression, i.e. a total dislocation density at the front must be in excess of this value by one or two orders. Consequently, due to extremely high stresses, at the front there exists a very unstable structure which is rearranged later with a noticeable decrease in dislocation density.

UNS A97075

Alloy Digest ◽  
1986 ◽  
Vol 35 (7) ◽  
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Aluminum Alloy ◽  
High Strength ◽  
Heat Treating ◽  
Good Resistance ◽  
Temperature Performance ◽  
Structural Applications ◽  
Structural Parts ◽  
Very High

Abstract UNS No. A97075 is a wrought precipitation-hardenable aluminum alloy. It has excellent mechanical properties, workability and response to heat treatment and refrigeration. Its typical uses comprise aircraft structural parts and other highly stressed structural applications where very high strength and good resistance to corrosion are required. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and shear strength as well as fatigue. It also includes information on low temperature performance as well as forming, heat treating, and machining. Filing Code: Al-269. Producer or source: Various aluminum companies.

WIELAND DURO TUNGSTEN

Alloy Digest ◽  
2020 ◽  
Vol 69 (10) ◽  
Keyword(s):  
Melting Point ◽  
Physical Properties ◽  
Tensile Properties ◽  
Modulus Of Elasticity ◽  
Radiation Shielding ◽  
High Melting ◽  
High Modulus ◽  
High Melting Point ◽  
Structural Applications ◽  
Very High

Abstract Wieland Duro Tungsten is unalloyed tungsten produced from pressed-and-sintered billets. The high melting point of tungsten makes it an obvious choice for structural applications exposed to very high temperatures. Tungsten is used at lower temperatures for applications that can benefit from its high density, high modulus of elasticity, or radiation shielding capability. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on machining. Filing Code: W-34. Producer or source: Wieland Duro GmbH.

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