Creep Behavior and Microstructures of Nb-26Ti-48Al Alloy and Composite

1994 ◽  
Vol 350 ◽  
Author(s):  
C. R. Feng ◽  
D. J. Michel
Keyword(s):  
Activation Energy ◽  
Creep Rate ◽  
Stress Exponent ◽  
Creep Behavior ◽  
Creep Testing ◽  
Combined Effects ◽  
Creep Mechanisms

AbstractThe creep behavior of Nb-26Ti-48Al alloy and its composite were investigated. After creep testing, precipitates were observed in the composite and mobile dislocations were found to be pinned by these precipitates. The combined effects of the reinforcements and the pinned dislocations were responsible for a reduced creep rate of the composite. The possible creep mechanisms were discussed based on the stress exponent and the activation energy of creep.

Microstructures and Creep of AM50-Sb-Gd Alloys

2005 ◽  
Vol 488-489 ◽  
pp. 749-752 ◽  
Author(s):  
Su Gui Tian ◽  
Keun Yong Sohn ◽  
Hyun Gap Cho ◽  
Kyung Hyun Kim
Keyword(s):  
Activation Energy ◽  
Creep Rate ◽  
Stress Exponent ◽  
Creep Behavior ◽  
Creep Deformation ◽  
Deformation Mechanism ◽  
Creep Resistance ◽  
Fine Particles ◽  
Dislocation Climb ◽  
The Matrix

Creep behavior of AM50-0.4% Sb-0.9%Gd alloy has been studied at temperatures ranging from 150 to 200°C and at stresses ranging from 40 to 90 MPa. Results show that the creep rate of AM50-0.4%Sb-0.9%Gd alloy was mainly controlled by dislocation climb at low stresses under 50 MPa. The activation energy for the creep was 131.2 ± 10 kJ/mol and the stress exponent was in the range from 4 to 9 depending on the applied stress. More than one deformation-mechanism were involved during the creep of this alloy. Microstructures of the alloy consist of a–Mg matrix and fine particles, distinguished as Mg17Al12, Sb2Mg3, and Mg2Gd or Al7GdMn5 that were homogeneously distributed in the matrix of the alloy, which effectively reduced the movement of dislocations, enhancing the creep resistance. Many dislocations were identified to be present on non-basal planes after creep deformation.

scholarly journals Microstructure and impression creep characteristics Al-9Si-xCu aluminum alloys

10.30544/101 ◽  
2015 ◽  
Vol 21 (2) ◽  
pp. 115-126 ◽  
Author(s):  
Mohsen Yousefi ◽  
Mehdi Dehnavi ◽  
S.M. Miresmaeili
Keyword(s):  
Activation Energy ◽  
Aluminum Alloys ◽  
Intermetallic Compound ◽  
Stress Exponent ◽  
Creep Behavior ◽  
Eutectic Phase ◽  
Dislocation Creep ◽  
Impression Creep ◽  
Pipe Diffusion ◽  
Creep Characteristics

The effects of 1.5, 2.5 and 3.5 wt.% Cu additions on the microstructure and creep behavior of the as-cast Al-9Si alloy were investigated by impression tests. The tests were performed at temperature ranging from 493 to 553 K and under punching stresses in the range 300 to 414 MPa for dwell times up to 3000 seconds. The results showed that, for all loads and temperatures, the Al–9Si–3.5Cu alloy had the lowest creep rates and thus, the highest creep resistance among all materials tested. This is attributed to the formation of hard intermetallic compound of Al2Cu, and higher amount of α-Al2Cu eutectic phase. The stress exponent and activation energy are in the ranges of 5.2- 7.2 and 115 -150 kJ/ mol, respectively for all alloys. According to the stress exponent and creep activation energies, the lattice and pipe diffusion- climb controlled dislocation creep were the dominant creep mechanism.

Creep Mechanisms in Niobium-Silicide Based In-Situ Composites

1998 ◽  
Vol 552 ◽  
Author(s):  
B. P. Bewlay ◽  
P. W. Whiting ◽  
A. W. Davis ◽  
C. L. Briant
Keyword(s):  
Creep Rate ◽  
Creep Behavior ◽  
Detrimental Effect ◽  
Higher Order ◽  
In Situ Composites ◽  
Niobium Silicide ◽  
Creep Mechanisms ◽  
Stress Levels ◽  
The Relationship

ABSTRACTThis paper will discuss the relationship between microstructure and creep behavior in hightemperature niobium-silicide based in-situ composites. The creep behavior of composites generated from binary Nb-Si alloys, and higher order alloys containing Mo, Hf and Ti additions, will be described. In-situ composites were tested in compression at temperatures up to 1200°C and stress levels in the range 70 to 280MPa. It was found that the Hf concentration can be increased to 7.5 with little increase in creep rate, over that for the binary Nb3Si-Nb composite, but at higher concentrations the creep rate is increased at stress levels higher than 21OMPa. At stresses less than 21OMPa the Ti concentration can be increased to 21 without a detrimental effect on creep performance, but at higher concentrations there is a substantial increase in the creep rate.

Comparison of the High-Temperature Deformation of Alumina-Zirconia and Alumina-Zirconia-Mullite Composites

2005 ◽  
Vol 20 (1) ◽  
pp. 13-17 ◽  
Author(s):  
Tiandan Chen ◽  
Martha L. Mecartney
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
Strain Rate ◽  
Stress Exponent ◽  
Creep Behavior ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Reactive Processing ◽  
Lower Activation ◽  
Lower Activation Energy

An alumina-based ceramic codispersed with 15 vol% zirconia and 15 vol% mullite (AZM) was synthesized by reactive processing, and the creep behavior was compared to alumina with 30 vol% zirconia (AZ). Constant stress compressive creep behavior for AZM exhibited a stress exponent of 2 and an activation energy of 770 KJ/mol, while a similar stress exponent but lower activation energy of 660 KJ/mol was found for AZ. The strain rate of AZM, however, was more than twice that of the AZ under the same deformation conditions, indicating a better potential for superplastic shape forming.

Elevated temperature mechanical behavior of CoSi and particulate reinforced CoSi produced by spray atomization and co-deposition

1994 ◽  
Vol 9 (2) ◽  
pp. 362-371 ◽  
Author(s):  
Don Baskin ◽  
Jeff Wolfenstine ◽  
Enrique J. Lavernia
Keyword(s):  
Activation Energy ◽  
Grain Size ◽  
Elevated Temperature ◽  
Stress Exponent ◽  
Creep Behavior ◽  
Diffusional Creep ◽  
Spray Atomization ◽  
Dislocation Glide ◽  
Unreinforced Material ◽  
Particulate Reinforced

Monolithic CoSi and TiB2 reinforced CoSi materials were produced by spray atomization and co-deposition. The creep behavior of both materials at elevated temperature was investigated. The unreinforced material of grain size ≍25 μm exhibited a stress exponent of three, activation energy for creep of 320 kJ/mole, dislocation substructure of homogeneously distributed dislocations, and inverse creep transients upon stress increases. These results suggest that the creep behavior of CoSi is controlled by a dislocation glide mechanism. In contrast, the reinforced material of a finer grain size (≍10 μm) exhibited a stress exponent of unity, activation energy for creep of 240 kJ/mole, and negligible creep transients upon stress increases, suggesting that the creep behavior of the reinforced material is controlled by a diffusional creep mechanism. The creep resistance of the reinforced material was lower than that for the unreinforced material. This is a result of the finer grain size and higher porosity in the reinforced material.

Effect of Plasma Nitriding on Creep Behavior at 550 °C of a Maraging Steel (300 Grade) Solution Annealed

2014 ◽  
Vol 802 ◽  
pp. 452-456 ◽  
Author(s):  
Adriano Gonçalves dos Reis ◽  
Danieli Aparecida Pereira Reis ◽  
Antônio Jorge Abdalla ◽  
Jorge Otubo
Keyword(s):  
Comparative Analysis ◽  
Creep Rate ◽  
Stress Exponent ◽  
Maraging Steel ◽  
Creep Behavior ◽  
Plasma Nitriding ◽  
Strong Impact ◽  
Stress Range ◽  
Creep Tests ◽  
Before And After

The objective of this work is to evaluate creep behavior of a maraging steel (300 grade) solution annealed before and after superficial treatment of plasma nitriding. Creep tests were conducted on a standard creep machine at stress range of 200 to 500 MPa at 550°C. Samples with a gage length of 18.5 mm and a diameter of 3.0 mm were used for all tests. Creep parameters are determined and a comparative analysis is established with the results gotten from the alloy with and without plasma nitriding. Maraging 300 steel plasma nitrided has showed a similar creep behavior compared with the same alloy without superficial treatment, with creep rate and stress exponent results very close to the material only solution annealed. This result can be associated with the strong impact of reversion of martensite to austenite and overaging at this temperature and time of exposure that minimizes the benefits of a superficial treatment.

Creep Behavior of Two Series Magnesium Alloys

2010 ◽  
Vol 638-642 ◽  
pp. 1596-1601 ◽  
Author(s):  
Yang Shan Sun ◽  
Jing Bai ◽  
Feng Xue
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Stress Exponent ◽  
Magnesium Alloys ◽  
Creep Behavior ◽  
Creep Deformation ◽  
Grain Boundary Sliding ◽  
Creep Tests ◽  
Sharp Drop ◽  
Creep Properties

The creep behavior of two series of magnesium alloys, Mg-4Al based alloys with strontium addition and binary Mg-Nd alloys, has been studied. Results show that the high creep properties achieved by the Mg-Nd alloys are attributed to the precipitation of tiny dispersed β’ particles, which form and effectively restrict the dislocation slipping and climb during creep deformation. In terms of values of the stress exponent and apparent activation energy gained from systematic creep tests, the mechanism responsible for creep deformation of the Mg-Nd alloys is inferred as dislocation climb, which is supported by TEM observations performed on the Mg-2Nd alloy after creep test. For the Mg-4Al based alloys, however, microstructural observations reveal that the significant improvement on creep properties caused by Sr addition is accounted for the formation of an interphase network consisting of Al4Sr and a Mg-Al-Sr ternary compound distributing at grain boundaries. The breakage of the interphase network after extrusion results in a sharp drop of creep properties, indicating the creep deformation of the alloy is controlled mainly by grain boundary sliding, which is in contradiction to the mechanism for creep of the alloys inferred by the classical criterions based on the values of stress exponent and apparent activation energy.

Creep Behavior of an Oxide Dispersion Strengthened Iron with Ultrafine Grain Structure

2010 ◽  
Vol 638-642 ◽  
pp. 3194-3199
Author(s):  
Valeriy Dudko ◽  
Rustam Kaibyshev ◽  
Andrey Belyakov ◽  
Yoshikazu Sakai ◽  
Kaneaki Tsuzaki
Keyword(s):  
Activation Energy ◽  
Stress Exponent ◽  
Creep Behavior ◽  
Deformation Behavior ◽  
Oxide Dispersion Strengthened ◽  
Lattice Diffusion ◽  
Grain Structure ◽  
Ultrafine Grain ◽  
Creep Data ◽  
Temperature Range

The creep behavior of oxide-bearing Fe-0.6%O steel was studied in the temperature range of 550-700°C at stresses ranging from 100 to 400 MPa. The creep data showed high values of an apparent stress exponent n close to 16 for power-law creep. In addition the apparent experimental activation energy was much higher than that for the lattice diffusion in -iron. Analysis of creep data revealed that the deformation behavior was strongly affected by the threshold stresses, which are associated with the interaction between moving dislocations and fine incoherent oxide particles. Analysis of deformation behavior in terms of threshold stress leads the true stress exponent of 8; the activation energy for creep became close to value of activation energy for lattice diffusion at 700°C and for pipe-diffusion in the temperature range of 550–650°C.

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