High Temperature Ductility Minimum in Rapidly Solidified Ni3Al - B

1984 ◽  
Vol 39 ◽  
Author(s):  
A. I. Taub ◽  
S. C. Huang ◽  
K. M. Chang
Keyword(s):  
Elevated Temperature ◽  
Flow Stress ◽  
Aluminum Concentration ◽  
Temperature Changes ◽  
Boron Doped ◽  
Boundary Stress ◽  
Increasing Temperature ◽  
Rapidly Solidified ◽  
Conventionally Cast ◽  
Ductility Minimum

ABSTRACTThe elevated temperature mechanical properties of rapidly solidified, boron doped Ni3Al have been investigated. Melt spun ribbon, plasma deposits and HIP'ped powder were tested with the same general results. It was found that the boron doped, rapidly solidified alloy exhibits an increasing flow stress with increasing temperature similar to that reported for conventionally cast Ni3Al. In addition, the rapidly solidified alloys exhibited a severe ductility minimum in the range 500–750C. The ductility minimum is relatively insensitive to both boron and aluminum concentration, but the embrittlement onset temperature changes with processing and testing parameters. In all cases, the onset of the ductility drop coincides with the onset of the decrease of the flow stress. It is postulated that this behavior is due to a change in the flow mechanism at elevated temperature to one that is associated with grain boundary stress concentration.

Microstructure and Plasticity of Hot Deformed 5083 Aluminum Alloy Produced by Rapid Solidification and Hot Extrusion / Badania Mikrostruktury I Plastyczności Odkształcanego Na Gorąco Szybko-Krystalizowanego I Wyciskanego Stopu Aluminium 5083

2012 ◽  
Vol 57 (4) ◽  
pp. 1253-1259 ◽  
Author(s):  
T. Tokarski ◽  
Ł. Wzorek ◽  
H. Dybiec
Keyword(s):  
Aluminum Alloy ◽  
High Temperature ◽  
Flow Stress ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Temperature Range ◽  
Rapidly Solidified ◽  
5083 Aluminum Alloy ◽  
Conventionally Cast

The objective of the present study is to analyze the mechanical properties and thermal stability for rapidly solidified and extruded 5083 aluminum alloy (RS). Compression tests were performed in order to estimate flow stress and strain rate sensitivity relation for 5083 alloy in the temperature range of 20°C to 450°C. For the comparison purposes, conventionally cast and extruded industrial material (IM) was studied as well. Deformation tests performed at room temperature conditions show that rapidly solidified material exhibits about 40% higher yield stress (YS=320 MPa) than conventionally cast material (YS=180 MPa), while the deformation at 450°C results in significant decrease of flow stress parameters for RS material (YS=20 MPa) in comparison to IM material (YS=40 MPa). Strain rate sensitivity parameter determined for high temperature conditions indicates superplasticity behavior of RS material. Structural observations show that under conditions of high-temperature deformation there are no operating recrystallization mechanisms. In general, grain size below 1µm and size of reinforcing phases below 50 nm is preserved within the used deformation temperature range.

Precipitation of chromium borides in annealed nickel aluminides

1990 ◽  
Vol 48 (4) ◽  
pp. 948-949
Author(s):  
G. Carro ◽  
J.E. Wittig ◽  
E.A. Kenik ◽  
W.F. Flanagan
Keyword(s):  
Elevated Temperature ◽  
Nickel Aluminide ◽  
Potential Problem ◽  
Intermetallic Phase ◽  
Chromium Boride ◽  
Boron Doped ◽  
Splat Quenching ◽  
Cold Rolled ◽  
Rapidly Solidified ◽  
Dynamic Embrittlement

Alloys based on the intermetallic phase, Ni3Al, are a class of materials noted for superior elevated temperature mechanical properties and oxidation resistance. Boron has been shown to increase ductility in these alloys and chromium additions to boron-doped nickel aluminide alloys have been reported to improve the high temperature properties by reducing dynamic embrittlement in oxidizing environments. However, a potential problem with these Ni-Al-Cr-B alloys is the depletion of chromium and boron at grain boundaries from chromium boride precipitation.Two alloys were investigated for elevated temperature chromium boride precipitation. The first, IC-218, has the composition (at%): 16.4 Al, 8.0 Cr, 0.4 Zr, 0.1 B, Ni bal., and the second, OR3B contains 15.0 Al, 10.0 Cr, 0.1 B, Ni bal.. Samples of both alloys were rapidly solidified into circular foils, 0.25 mm thick, by splat quenching between two copper plates. Also, cold rolled and recrystallized sheet, 3 mm thick, of IC-218 was used for comparison.

Monitoring of Thermal Degradation of Fireproof Coating

2012 ◽  
Vol 598 ◽  
pp. 379-383 ◽  
Author(s):  
Tomáš Chrebet ◽  
Jozef Martinka ◽  
Karol Balog ◽  
Ivan Hrušovský
Keyword(s):  
Elevated Temperature ◽  
Thermal Degradation ◽  
Fire Resistance ◽  
Air Atmosphere ◽  
Article Deal ◽  
Increasing Temperature ◽  
Fireproof Coating ◽  
Coating Weight ◽  
Fixed Period ◽  
Intended Use

Under the fire conditions, the resistance of cable distribution is required for a fixed period, depending on the intended use of the cable. To increase the fire resistance of cables a fireproof coating may be applied. Article deal with the behavior of the fireproof coating during elevated temperature. Concretely, the aim is monitored a coating weight change under the conditions of dynamically increasing temperature and with or without using air-flow. It is also monitored the change in weight, depending on the isothermal temperatures in dynamic air atmosphere.

Prediction of flow stress and textures of AZ31 magnesium alloy at elevated temperature

2014 ◽  
Vol 94 (29) ◽  
pp. 3353-3367 ◽  
Author(s):  
Hesam Askari ◽  
John P. Young ◽  
David P. Field ◽  
Ghassan Kridli ◽  
Hussein M. Zbib
Keyword(s):  
Elevated Temperature ◽  
Flow Stress ◽  
Magnesium Alloy ◽  
Az31 Magnesium Alloy

In situ transmission electron microscope measurements of solid Al-solid Pb and solid Al-liquid Pb surface-energy anisotropy in rapidly solidified Al-5% Pb (by mass)

1987 ◽  
Vol 414 (1847) ◽  
pp. 499-507 ◽  
Keyword(s):  
Electron Microscope ◽  
Melting Point ◽  
Surface Energy ◽  
Transmission Electron Microscope ◽  
Room Temperature ◽  
Transmission Electron ◽  
Increasing Temperature ◽  
Rapidly Solidified ◽  
Al Matrix

Alloys of Al-5% Pb and Al-5% Pb-0.5% Si (by mass) have been manufactured by rapid solidification and then examined by transmission electron microscopy. The rapidly solidified alloy microstructures consist of 5-60 nm Pb particles embedded in an Al matrix. The Pb particles have a cube-cube orientation relation with the Al matrix, and are cub-octahedral in shape, bounded by {100} Al, Pb and {111} Al, Pb facets. The equilibrium Pb particle shape and therefore the anisotropy of solid Al-solid Pb and solid Al-liquid Pb surface energies have been monitored by in situ heating in the transmission electron microscope over the temperature range between room temperature and 550°C. The ani­sotropy of solid Al-solid Pb surface energy is constant between room temperature and the Pb melting point, with a {100} Al, Pb surface energy about 14% greater than the {111} Al, Pb surface energy, in good agreement with geometric near-neighbour bond energy calculations. The {100} AI, Pb facet disappears when the Pb particles melt, and the anisotropy of solid Al-liquid Pb surface energy decreases gradually with increasing temperature above the Pb melting point, until the Pb particles become spherical at about 550°C.

Effect of Aluminum Concentration And Boron Dopant on Environmental Embriitlement In Feal Aluminides

1990 ◽  
Vol 213 ◽  
Author(s):  
C. T. Liu ◽  
E. P. George
Keyword(s):  
Aluminum Alloys ◽  
Grain Boundaries ◽  
Aluminum Concentration ◽  
Al Alloy ◽  
Test Environment ◽  
Environmental Embrittlement ◽  
Boron Doped ◽  
Weak Boundaries ◽  
Boron Dopant ◽  
Strong Segregation

ABSTRACTThe room-temperature tensile properties of FeAl aluminides were determined as functionsof aluminum concentration (35 to 43 at. % Al), test environment, and surface (oil) coating. The two lower aluminum alloys containing 35 and 36.5% Al are prone to severe environmental embrittlement, while the two higher aluminum alloys with 40 and 43% Al are much less sensitive to change in test environment and surface coating. The reason for the different behavior is that the grain boundaries are intrinsically weak in the higher aluminum alloys, and these weak boundaries dominate the low ductility and brittle fracture behavior of the 40 and 43% Al alloys. When boron is added to the 40% Al alloy as a grain-boundary strengthener, the environmental effect becomes prominent. In this case, the tensile ductility of the boron-doped alloy, just like that of the lower aluminum alloys, can be dramatically improved by control of test environment (e.g. dry oxygen vs air). Strong segregation of boron to the grain boundaries, with a segregation factor of 43, was revealed by Auger analyses.

Tensile Deformation Behavior of 5A90 Al-Li Alloy Sheet at Elevated Temperature

2011 ◽  
Vol 66-68 ◽  
pp. 70-75 ◽  
Author(s):  
Gao Shan Ma ◽  
Song Yang Zhang ◽  
Han Ying Wang ◽  
Min Wan
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Deformation Behavior ◽  
Tensile Deformation ◽  
Alloy Sheet ◽  
Hot Forming ◽  
Uniaxial Tensile ◽  
Sensitivity Index ◽  
Tensile Deformation Behavior ◽  
Increasing Temperature

Uniaxial tensile deformation behavior of 5A90 aluminium-lithium alloy sheet is investigated in the hot forming with the temperature range of 200-450°C and strain rate range of 0.3×10-3-0.2×10-1s-1. It is found that the flow stress of 5A90 Al-Li alloy in uniaxial tension increase with increasing strain rate and decrease with increasing temperature, however, the tendency of total elongation is just the reverse, and the optimum forming temperature is 400°C. The strain rate sensitivity index (m-value) remarkably increases with increasing temperature for a given strain rate. It is shown that 5A90 Al-Li alloy sheet displays the sensitivity to the strain rate at elevated temperatures. For a given strain rate, the strain hardening index (n-value) decreases with increasing temperature, whereas the n-value increases above 350°C. The constitutive equation of stress, strain and strain rate for 5A90 Al-Li alloy at any temperature is obtained by fitting the experimental data, which gave a good flow stress model for the FEM simulation of hot forming.

Temperature and Strain Rate Effects on Mechanical Behavior of a PMMA

2007 ◽  
Vol 340-341 ◽  
pp. 1079-1084 ◽  
Author(s):  
Tao Suo ◽  
Yu Long Li ◽  
Yuan Yong Liu
Keyword(s):  
Flow Stress ◽  
High Strain Rate ◽  
Strain Rate ◽  
Mechanical Behavior ◽  
High Strain ◽  
Strain Range ◽  
Testing Temperature ◽  
Strain Rate Effects ◽  
Rate Effects ◽  
Increasing Temperature

In this paper, the mechanical behavior of a PMMA used as the windshield of aircraft was tested. The experiments were finished under two quasi-static strain rates and a high strain rate with the testing temperature from 299K to 373K. The results show that the mechanical property of this PMMA depends heavily on the testing temperature. The Young’s modulus and flow stress were found to decrease with increasing temperature at low strain rate. At the strain rate of 10-1 1/s, strain softening was observed under all experiment temperatures. At high strain rate, with the temperature increasing, the flow stress decreases remarkably while the failure strain increases, and the strain soften was also observed at the temperature above 333K. Comparing the experiments results at same temperature, it was found the flow stress increases with the rising strain rate. The predictions of the mechanical behavior using the ZWT theoretical model have a good agreement with experimental results in the strain range of 8%.

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