Plastic Deformation Of AI-Cu-Fe Icosahedral Quasicrystals

1998 ◽  
Vol 553 ◽  
Author(s):  
E. Giacometti ◽  
N. Baluc ◽  
J. Bonneville
Keyword(s):  
Plastic Deformation ◽  
Transition Temperature ◽  
Flow Stress ◽  
Constant Strain Rate ◽  
Friction Stress ◽  
Plastic Strains ◽  
Total Flow ◽  
Brittle To Ductile Transition ◽  
Slip Bands ◽  
Icosahedral Quasicrystals

AbstractPoly-quasicrystalline specimens of the Al-Cu-Fe system have been pre-strained and further deformed at various temperatures, above and below the brittle-to-ductile transition temperature, under constant strain-rate conditions. The experiments have been specially designed to examine the respective contributions of the thermally reversible and structural dependent parts to the total flow stress. We show that the so-called internal stress, which results from the deformation builtin microstructure, has a rather low value, if any. In addition, the flow stress is found to be fully temperature reversible, if one takes into account previous plastic strains. We suggest that these results can be explained by a weakening of the friction stress, due to the formation of soft slip bands.

Precipitate coarsening during hot-compression testing of NiAl + 2 at.% Nb

1986 ◽  
Vol 44 ◽  
pp. 598-599
Author(s):  
W. M. Sherman ◽  
K. M. Vedula
Keyword(s):  
High Temperature ◽  
Flow Stress ◽  
Weight Ratio ◽  
Constant Strain Rate ◽  
Hot Compression ◽  
Compression Testing ◽  
Second Phase ◽  
Precipitate Coarsening ◽  
High Temperature Mechanical Properties ◽  
Ordered Intermetallic

The strength to weight ratio and oxidation resistance of NiAl make this ordered intermetallic, with some modifications, an attractive candidate to compete with many superalloys for high temperature applications. Recent studies have shown that the inherent brittleness of many polycrystalline intermetallics can be overcome by micro and macroalloying. It has also been found that the high temperature mechanical properties of NiAl can be enhanced through the addition of Nb by powder metallurgical techniques forming a dispersed second phase through interdiffusion in a polycrystalline matrix. A drop in the flow stress is observed however in a NiAl-2 at.% Nb alloy after 0.2 % strain during constant strain rate hot compression testing at 1025°C. The object of this investigation was to identify the second phase and to determine the cause of the flow stress drop.

scholarly journals The plastic deformation of iron and the formation of Neumann lines

1925 ◽  
Vol 108 (745) ◽  
pp. 231-231
Keyword(s):  
Plastic Deformation ◽  
Pure Iron ◽  
Crystal Surfaces ◽  
Size And Shape ◽  
Slip Bands ◽  
Wide Range ◽  
Moderate Rate ◽  
Rapid Deformation

The object of the investigation described in the present paper was to ascertain the manner in which wide variations in speed affect the mechanism of deformation in plastic metals. Iron was selected as the first metal for experiment, mainly because it is known that rapid deformation produced by shock is accompanied in this metal by special features, known as Neumann lines or lamellæ. When a piece of nearly pure iron, of suitable size and shape, with one face polished and etched, is subsequently subjected to plastic deformation at a moderate rate, the crystal surfaces, when examined under the microscope after deformation, show the well-known appearance of slip bands (1). The present experiments were undertaken in the first instance to ascertain whether the character, number and appearance of such slip bands would be appreciably affected by varying the rate of deformation over a wide range. For the sake of convenience, deformation by compression has been employed, the metal being used in the form of small rectangular prisms, measuring in some instances 0.44 inch by 0.44 inch in section by 0.7 inch in height.

Effect of Hydrogen on the Development of Superplastic Deformation in the Submicrocrystalline Ti–6Al–4V Alloy

2016 ◽  
Vol 838-839 ◽  
pp. 344-349 ◽  
Author(s):  
Galina P. Grabovetskaya ◽  
Ekaterina N. Stepanova ◽  
Ilya V. Ratochka ◽  
I.P. Mishin ◽  
Olga V. Zabudchenko
Keyword(s):  
Solid Solution ◽  
Plastic Deformation ◽  
Flow Stress ◽  
Superplastic Deformation ◽  
Deformation Localization ◽  
Solid Solution Strengthening ◽  
Solution Strengthening ◽  
Hydrogenation Effect

Hydrogenation effect on the development of superplastic deformation in the submicrocrystalline Ti–6Al–4V alloy at temperatures (0.4–0.5)Тmelt is investigated. Hydrogenation of the submicrocrystalline Ti–6Al–4V alloy to 0.26 mass% during superplastic deformation is found to result in solid solution strengthening, plastic deformation localization, and as a consequence, decrease of the deformation to failure. Possible reasons for the decrease of the flow stress and increase of the deformation to failure in the submicrocrystalline Ti–6Al–4V–0.26H alloy during deformation under conditions of superplasticity and simultaneous hydrogen degassing from the alloy are discussed.

Deformation mechanisms in MoSi2at temperatures above the brittle-to-ductile transition temperature

1997 ◽  
Vol 75 (1) ◽  
pp. 17-30 ◽  
Author(s):  
Daniel J. Evans ◽  
Frank J. Scheltens ◽  
John B. Woodhouse ◽  
Hamish L. Fraser
Keyword(s):  
Transition Temperature ◽  
Deformation Mechanisms ◽  
Brittle To Ductile Transition

The Experimental Determination of the Friction Stress between the Semi-Product and the Active Plate at the Multiaxial Forging of Copper

2014 ◽  
Vol 803 ◽  
pp. 216-221 ◽  
Author(s):  
Alin Marian Cazac ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
Cristian Predescu ◽  
Andrei Victor Sandhu ◽  
Costică Bejinariu
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Friction Force ◽  
Friction Stress ◽  
Severe Plastic Deformation Processing ◽  
Total Force ◽  
Finished Part ◽  
Closed Die Forging ◽  
Deformation Force

The paper aims the determination of the friction force by means of external friction stress, at the severe plastic deformation processing using cyclic closed-die forging method. It is known that the total force used at the severe plastic deformation by the method of multiaxial forging is being composed by the deformation force itself and the friction force between the semi-product and the deformation tools. Once the friction stresses known, for a certain material, one can determine the friction force corresponding for a given deformation of a semi-product of a particular shape and sizes. By means of the flowing curve of the semi-product material one can determine the deformation force, which together with the friction force give the total necessary force for a deformation and so one can choose the necessary equipment for the processing of the material by severe plastic deformation. For this purpose it has been severely plastic deformed by the method of multiaxial forging, a semi-product having the sizes 10x10x20 mm, the finished part having the same sizes and shape. It has been measured the deformation force and the extraction force of the finished part from the cavity of the active plate, the late being used for the determination of the friction stress between the semi-product and the active plate.

Flow Behaviour of M2 Steel Alloy during Semi Solid Isothermal Rapid Compression

2012 ◽  
Vol 192-193 ◽  
pp. 311-316
Author(s):  
Farzad Hosseini Yekta ◽  
S.A. Sadough ◽  
Vahid Pouyafar ◽  
Amin Jabbari
Keyword(s):  
Flow Stress ◽  
Tool Steel ◽  
Constant Strain Rate ◽  
Special Kind ◽  
Holding Time ◽  
Plastic Behavior ◽  
Steel Alloy ◽  
Rapid Compression ◽  
Ram Speed ◽  
Semi Solid

The key to all semisolid processes is spherical and non-dendritic particles suspended in a liquid matrix. This special kind of microstructure causes the semisolid material to behave like a non-Newtonian fluid dependent on time and shear rate. Semi solid metal processing gives less shrinkage and porosity, non-macro segregation, lower flow stress, good formability and increased die life compared with conventional production methods. Therefore, semi solid processing introduces a good option for massive forming of high temperature alloys. Here, by partial remelting of M2 tool steel alloy under rapid compression test, deformation mechanism of steel alloy and its correlation to rheological properties were investigated. Flow stress for M2 tool steel alloy corresponding to solid fraction above 55% derived at constant strain rate and holding time. In order to investigate the parameter involved in this process, in the second stage of experiments the ram speed and holding time are variable. The analysis of the derived curves shows that the semisolid slurries exhibit a pseudo plastic behavior dependent on stain rate and temperature. The classical power law model used to describe the rheological and thixotropic dependence.

Predicting the Brittle-to-Ductile Transition Temperatures for Surface Cracks in Pipeline Girth Welds: It’s Better Than You Thought

2008 ◽  
Author(s):  
Gery Wilkowski ◽  
David Rudland ◽  
Do-Jun Shim ◽  
David Horsley
Keyword(s):  
Transition Temperature ◽  
Surface Crack ◽  
Master Curve ◽  
Crack Depth ◽  
Temperature Shift ◽  
Transition Temperatures ◽  
Surface Cracks ◽  
Line Pipe ◽  
Brittle To Ductile Transition ◽  
Girth Welds

A methodology to predict the brittle-to-ductile transition temperature for sharp or blunt surface-breaking defects in base metals was developed and presented at IPC 2006. The method involved applying a series of transition temperature shifts due to loading rate, thickness, and constraint differences between bending versus tension loading, as well as a function of surface-crack depth. The result was a master curve of transition temperatures that could predict dynamic or static transition temperatures of through-wall cracks or surface cracks in pipes. The surface-crack brittle-to-ductile transition temperature could be predicted from either Charpy or CTOD bend-bar specimen transition temperature information. The surface crack in the pipe has much lower crack-tip constraint, and therefore a much lower brittle-to-ductile transition temperature than either the Charpy or CTOD bend-bar specimen transition temperature. This paper extends the prior work by presenting past and recent data on cracks in line-pipe girth welds. The data developed for one X100 weld metal shows that the same base-metal master curve for transition temperatures works well for line-pipe girth welds. The experimental results show that the transition temperature shift for the surface-crack constraint condition in the weld was about 30C lower than the transition temperature from standard CTOD bend-bar tests, and that transition temperature difference was predicted well. Hence surface cracks in girth welds may exhibit higher fracture resistance in full-scale behavior than might be predicted from CTOD bend-bar specimen testing. These limited tests show that with additional validation efforts the FITT Master Curve is appropriate for implementation to codes and standards for girth-weld defect stress-based criteria. For strain-based criteria or leak-before-break behavior, the pipeline would have to operate at some additional temperature above the FITT of the surface crack to ensure sufficient ductile fracture behavior.

Flow Stress and Elongation of Superplastic Deformation in La55Al25Ni20 Metallic Glass

1999 ◽  
Vol 601 ◽  
Author(s):  
Y. Kawamura ◽  
A. Inoue
Keyword(s):  
Flow Stress ◽  
Metallic Glass ◽  
Strain Rate ◽  
Superplastic Deformation ◽  
Constant Strain Rate ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Liquid Region ◽  
Elongation To Failure ◽  
Crosshead Velocity

AbstractWe have investigated the flow stress and elongation of superplastic deformation in a La55Al25Ni20 (at%) metallic glass that has a wide supercooled liquid region of 72 K before crystallization. The superplasticity that appeared in the supercooled liquid region was generated by the Newtonian viscous flow that exhibits the m value of unity. The elongation to failure was restricted by the transition of the Newtonian flow to non-Newtonian one and the crystallization during deformation. We succeeded in establishing the constitutive formulation of the flow stress in the supercooled liquid region. Its formulation was expressed very well by a stretched exponential function σflow=Dε exp(H*/RT) [1-exp(E/{ε exp(H**/RT)}0.82)]. Formulations describing the elongation to failure in constant-strain-rate and constant-crosshead velocity tests were, moreover, established. It was found from the simulation that the maximum elongation in the constant-strain-rate test reached more than 106% which was two orders of magnitude larger than that in the constant-crosshead-velocity test.

Strain-rate dependence of hardening and softening in compression of a bulk-metallic glass

2007 ◽  
Vol 22 (10) ◽  
pp. 2655-2658 ◽  
Author(s):  
W.H. Jiang ◽  
F.X. Liu ◽  
F. Jiang ◽  
K.Q. Qiu ◽  
H. Choo ◽  
...  
Keyword(s):  
Flow Stress ◽  
Metallic Glass ◽  
Strain Rate ◽  
Bulk Metallic Glass ◽  
Plastic Flow ◽  
Shear Banding ◽  
Constant Strain Rate ◽  
Rate Dependence ◽  
Strain Rate Dependence ◽  
Plastic Flow Stress

We investigated the effect of strain rate on the plastic-flow stress of a Zr-based bulk-metallic glass in quasistatic compression. The results indicate that the plastic-flow stress is dependent on the strain rate: an increase in the strain rate leads to a decrease in the plastic-flow stress, and vice versa. However, simply loading, unloading, and reloading at a constant strain rate do not change the plastic-flow stress. This strain-rate dependence of the plastic-flow stress may be related to shear-banding operations.

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