scholarly journals Creep Mechanisms of an Al–Cu–Mg Alloy at the Macro- and Micro-Scale: Effect of the S′/S Precipitate

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 2907 ◽  
Author(s):  
Yongqian Xu ◽  
Lingwei Yang ◽  
Lihua Zhan ◽  
Hailiang Yu ◽  
Minghui Huang
Keyword(s):  
Steady State ◽  
Steady State Creep ◽  
Creep Mechanism ◽  
Mg Alloy ◽  
Tensile Creep ◽  
Precipitate Size ◽  
Minor Role ◽  
Al Alloy ◽  
Creep Tests ◽  
Precipitate Growth

A novel methodology combining the macro- and micro-creep techniques was employed to study the effect of S′/S precipitate growth on the creep mechanism of an Al–Cu–Mg alloy. An AA2524 alloy was pre-aged at 180 °C to obtain S′/S precipitates with various sizes. The results showed that the precipitate size increased approximately linearly to ≈32 nm, ≈60 nm, and ≈105 nm after 3 h, 6 h, and 12 h of pre-aging, respectively. The growth of precipitate could significantly shorten the primary creep stage, despite the fact that the steady-state creep behavior was similar to that of the as-received alloy, as revealed by the macro tensile creep tests at 180 °C and 180 MPa. This led to a stress exponent (2.4–2.5) of the Al alloy with various precipitate sizes that was quite close to that of the as-received Al alloy, implying a steady-state creep mechanism dominated by grain boundary sliding and dislocation interactions. Finally, the micro-creep tests showed a minor role of the precipitate size on the steady-state creep mechanism, as evidenced by the similar strain rate sensitivity (0.0169–0.0186), activation volume (≈27 b3), and the results of a detailed transmission electron microscopy analysis of all tested alloys.

Improved tensile creep properties of yttrium- and lanthanum-doped alumina: a solid solution effect

2001 ◽  
Vol 16 (2) ◽  
pp. 425-429 ◽  
Author(s):  
Junghyun Cho ◽  
Chong Min Wang ◽  
Helen M. Chan ◽  
J. M. Rickman ◽  
Martin P. Harmer
Keyword(s):  
Solid Solution ◽  
Steady State ◽  
Creep Behavior ◽  
Solubility Limit ◽  
Steady State Creep ◽  
Tensile Creep ◽  
Creep Properties ◽  
Uniform Microstructure ◽  
Equiaxed Grains ◽  
Rare Earth Doped

The tensile creep behavior of yttrium- and lanthanum-doped alumina (at dopant levels below the solubility limit) was examined. Both compositions (100 ppm yttrium, 100 ppm lanthanum) exhibited a uniform microstructure consisting of fine, equiaxed grains. The creep resistance of both doped aluminas was enhanced, compared with undoped alumina, by about two orders of magnitude, which was almost the same degree of improvement as for materials with higher dopant levels (in excess of the solubility limit). In addition, measured creep rupture curves exhibited predominantly steady-state creep behavior. Our results, therefore, verified that the creep improvement in these rare-earth doped aluminas was primarily a solid-solution effect.

ACTIVATION ENERGY FOR CREEP OF TIN

1958 ◽  
Vol 36 (11) ◽  
pp. 1445-1449 ◽  
Author(s):  
L. G. Bonar ◽  
G. B. Craig
Keyword(s):  
Activation Energy ◽  
Steady State ◽  
High Purity ◽  
Steady State Creep ◽  
Temperature Cycling ◽  
Constant Stress ◽  
Creep Tests ◽  
Temperature Range ◽  
A Value

The literature reports values ranging from 8000 to 26,000 cal per g-atom for the activation energy for the creep of tin. The present investigation analyzed the results of constant stress creep tests during steady state creep, and by means of temperature cycling. A value of approximately 9000 cal per g-atom for the creep of high purity tin in the temperature range 300 to 350° K was obtained.

scholarly journals ɤ-TiAl Alloy: Tensile Creep Deformation Behaviour and Creep Life at 832 °C

2021 ◽  
Author(s):  
Mainak Saha
Keyword(s):  
Steady State ◽  
Creep Deformation ◽  
Original Work ◽  
Single Phase ◽  
Tial Alloy ◽  
Deformation Behaviour ◽  
Steady State Creep ◽  
Tensile Creep ◽  
Creep Life ◽  
Processing Techniques

Creep deformation in single phase ɤ-TiAl alloy manufactured using different processing techniques has been an extensively studied topic since the late 1970s. The present work revisits the original work on understanding the tensile creep deformation behaviour of wrought single-phase ɤ-TiAl alloy by Hayes and Martin [1] and is aimed to develop an understanding of steady state creep. Besides, it is also aimed to investigate the creep life for stress levels of 69.4 and 103.4 MPa at 832 ⁰C using Monkman-Grant [2] approach.

scholarly journals Deformation of Floating Ice Shelves

1957 ◽  
Vol 3 (21) ◽  
pp. 38-42 ◽  
Author(s):  
J. Weertman
Keyword(s):  
Steady State ◽  
Creep Rate ◽  
Creep Deformation ◽  
Plasticity Theory ◽  
Steady State Creep ◽  
Creep Tests ◽  
Ice Shelves ◽  
The Antarctic ◽  
Good Agreement

AbstractThe problem of the creep deformation of floating ice shelves is considered. The problem is solved using Glen’s creep law for ice and Nye’s relation of steady-state creep (the analogue of the Lévy-Miles relation in plasticity theory). Good agreement is obtained between an observed creep rate at Maudheim in the Antarctic and that predicted from the results of creep tests made by Glen.

Tensile Creep Behavior of NiAl-9Mo Eutectic Alloy

2005 ◽  
Vol 475-479 ◽  
pp. 763-766 ◽  
Author(s):  
Wei Li Ren ◽  
Jian Ting Guo ◽  
Gu Song Li ◽  
Jian Sheng Wu
Keyword(s):  
Steady State ◽  
Eutectic Alloy ◽  
Creep Behavior ◽  
Dislocation Climb ◽  
Steady State Creep ◽  
Tensile Creep ◽  
Final Fracture ◽  
Colony Boundary ◽  
Kinetics Of ◽  
Nial Matrix

The tensile creep behavior of NiAl-9Mo eutectic alloy has been investigated over a stress range of 50 to 100MPa at the temperatures ranging from 850 to 950°C. All of the creep curves exhibit the very long steady-state stage. The creep parameters and TEM observations indicates the kinetics of the steady-state creep deformation is governed by dislocation climb in the NiAl matrix phase. The crack origination and development at the colony boundary results in the onset of tertiary creep stage and final fracture of the alloy.

Effect of Sb Addition on the Creep Property of AZ31 Alloy

2004 ◽  
Vol 449-452 ◽  
pp. 641-644 ◽  
Author(s):  
Su Gui Tian ◽  
Keun Yong Sohn ◽  
Kyung Hyun Kim
Keyword(s):  
Steady State ◽  
Volume Fraction ◽  
Creep Property ◽  
High Volume ◽  
Az31 Alloy ◽  
Constant Load ◽  
Steady State Creep ◽  
Steady State Creep Rate ◽  
Creep Tests ◽  
Second Phases

The effects of antimony addition on the microstructures and creep behavior of AZ31 have been studied. Constant load creep tests were carried out at 200°C and an initial stress of 50MPa for AZ31 alloys containing antimony up to 0.84% by weight. Results show that Small additions of antimony to AZ31 effectively decreased the creep extension and steady state creep rates. The steady state creep rate of AZ31 was reduced 2.5 times by the addition of 0.84% of antimony by weight. The main reason for the higher creep resistance is due to the presence of high volume fraction (~20%) of second phases including Mg3Sb2, which effectively hindered the movement of dislocations during the elevated temperature creep.

Constitutive Behavior and Low Cycle Thermal Fatigue of 97Sn-3Cu Solder Joints

1993 ◽  
Vol 115 (2) ◽  
pp. 147-152 ◽  
Author(s):  
Y.-H. Pao ◽  
S. Badgley ◽  
E. Jih ◽  
R. Govila ◽  
J. Browning
Keyword(s):  
Steady State ◽  
Constitutive Equation ◽  
Thermal Fatigue ◽  
Solder Joints ◽  
Steady State Creep ◽  
Creep Mechanism ◽  
Beam Specimen ◽  
Finite Element Program ◽  
Cyclic Shear ◽  
Element Program

The thermal cyclic shear stress/strain hysteresis response and associated steady-state creep parameters of 97Sn-3Cu solder joints have been determined using a beam specimen previously developed by Pao et al. (1992a). The solder joint was subjected to a 40-minute thermal cycling from 40°C to 140°C. A constitutive equation based on elastic and steady-state creep deformation for the solder has been formulated and implemented in a finite element program, ABAQUS, to model the experiment. The results show that the constitutive equation based on one single creep mechanism cannot fully account for the deformation during cooling, as opposed to the case of 90Pb-10Sn where the entire cyclic deformation can be well modeled by a similar constitutive equation (Pao et al., 1992c). This suggests that another creep mechanism is dominant for lower stresses and higher temperature. The thermal fatigue results show that the failure mechanism of 97Sn-3Cu joints is similar to that of 90Pb-10Sn joints, but the number of cycles to failure of 97Sn-Cu solder joints is at least 5 times longer than 90Pb-10Sn solder joints. This indicates the potential application of 97Sn-3Cu in place of 90Pb-10Sn solder.

Creep Contributes to the Fatigue Behavior of Bovine Trabecular Bone

1998 ◽  
Vol 120 (5) ◽  
pp. 647-654 ◽  
Author(s):  
S. M. Bowman ◽  
X. E. Guo ◽  
D. W. Cheng ◽  
T. M. Keaveny ◽  
L. J. Gibson ◽  
...  
Keyword(s):  
Steady State ◽  
Creep Rate ◽  
Trabecular Bone ◽  
Fatigue Behavior ◽  
Slow Crack Growth ◽  
Hysteresis Loops ◽  
Steady State Creep ◽  
Time To Failure ◽  
Steady State Creep Rate ◽  
Creep Tests

Repetitive, low-intensity loading from normal daily activities can generate fatigue damage in trabecular bone, a potential cause of spontaneous fractures of the hip and spine. Finite element models of trabecular bone (Guo et al., 1994) suggest that both creep and slow crack growth contribute to fatigue failure. In an effort to characterize these damage mechanisms experimentally, we conducted fatigue and creep tests on 85 waisted specimens of trabecular bone obtained from 76 bovine proximal tibiae. All applied stresses were normalized by the previously measured specimen modulus. Fatigue tests were conducted at room temperature; creep tests were conducted at 4, 15, 25, 37, 45, and 53°C in a custom-designed apparatus. The fatigue behavior was characterized by decreasing modulus and increasing hysteresis prior to failure. The hysteresis loops progressively displaced along the strain axis, indicating that creep was also involved in the fatigue process. The creep behavior was characterized by the three classical stages of decreasing, constant, and increasing creep rates. Strong and highly significant power-law relationships were found between cycles-to-failure, time-to-failure, steady-state creep rate, and the applied loads. Creep analyses of the fatigue hysteresis loops also generated strong and highly significant power law relationships for time-to-failure and steady-state creep rate. Lastly, the products of creep rate and time-to-failure were constant for both the fatigue and creep tests and were equal to the measured failure strains, suggesting that creep plays a fundamental role in the fatigue behavior of trabecular bone. Additional analysis of the fatigue strain data suggests that creep and slow crack growth are not separate processes that dominate at high and low loads, respectively, but are present throughout all stages of fatigue.

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