scholarly journals Room-Temperature Creep Behavior and Activation Volume of Dislocation Nucleation in a LiTaO3 Single Crystal by Nanoindentation

Materials ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1683 ◽  
Author(s):  
Yi Ma ◽  
Xianwei Huang ◽  
Yuxuan Song ◽  
Wei Hang ◽  
Taihua Zhang
Keyword(s):  
Creep Deformation ◽  
Room Temperature ◽  
Activation Volume ◽  
Rate Sensitivity ◽  
Dislocation Nucleation ◽  
Orientation Effect ◽  
Plastic Behavior ◽  
Mechanical Heterogeneity ◽  
Temperature Creep ◽  
Room Temperature Creep

The crystal orientation effect on mechanical heterogeneity of LiTaO3 single crystals is well known, whilst the time-dependent plastic behavior, i.e., creep is still short of understanding. Relying on nanoindentation technology, we systematically studied room-temperature creep flows at various holding depths (100 nm to 1100 nm) in three typical orientations namely the X-112°, Y-36° and Y-42° planes. Creep resistance was much stronger in the X-112° plane than the others. In the meanwhile, creep features were similar in the Y-36° and Y-42° planes. The orientation effect on creep deformation was consistent with that on hardness. The nanoindentation length scale played an important role in creep deformation that creep strains were gradually decreased with the holding depth in all the planes. Based on strain rate sensitivity and yield stress, the activation volumes of dislocation nucleation were computed at various nanoindentation depths. The activation volumes ranged from 5 Å3 to 23 Å3 for the Y-36° and Y-42° planes, indicating that a point-like defect could be the source of plastic initiation. In the X-112° plane, the activation volume was between 6 Å3 and 83 Å3. Cooperative migration of several atoms could also be the mechanism of dislocation activation at deep nanoindentation.

scholarly journals On the Room-Temperature Creep Behavior and Its Correlation with Length Scale of a Litao3 Single Crystal by Spherical Nanoindentation

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4213
Author(s):  
Wei Hang ◽  
Xianwei Huang ◽  
Min Liu ◽  
Yi Ma
Keyword(s):  
Strain Rate ◽  
Single Crystal ◽  
Creep Behavior ◽  
Creep Deformation ◽  
Room Temperature ◽  
Length Scale ◽  
Compression Stress ◽  
Temperature Creep ◽  
Strain And Strain Rate ◽  
Room Temperature Creep

Relying on nanoindentation technology, the room-temperature creep behavior of a LiTaO3 single crystal in the typical orientation (01 1 ¯ 2), i.e., Y-42° plane was investigated. Three kinds of spherical tips with the radii of 0.76, 2.95 and 9.8 μm were respectively applied to detect nanoindentation length scale effect on creep deformation at both elastic and plastic regions. Superficially, both creep displacement and rate were nearly linearly increased with increasing holding depth and independent of tip size, which could be ascribed to the simultaneously enlarged holding strain and deformation volume beneath the indenter. At a similar holding strain, creep deformation, i.e., creep strain and strain rate were more pronounced under smaller spherical tips. Strain rate sensitivities of creep flows under different spherical tips and holding strains were also estimated. The potential room-temperature creep mechanism of LiTaO3 under high shear compression stress was discussed.

Effect of Cryogenic Treatment on Creep Resistance of Cu-11.74Al-0.38Ni Alloy

2014 ◽  
Vol 508 ◽  
pp. 102-105
Author(s):  
Rong Hua Zhang ◽  
Biao Wu ◽  
Xiao Ping Zheng
Keyword(s):  
Creep Deformation ◽  
Creep Resistance ◽  
Room Temperature ◽  
Applied Load ◽  
Cryogenic Treatment ◽  
Optical Microscope ◽  
Temperature Creep ◽  
Before And After ◽  
Room Temperature Creep

In order to explore the effect of cryogenic treatment on creep resistance of Cu-11.74Al-0.38Ni alloy at room temperature, the room temperature creep deformation of Cu-11.74Al-0.38Ni alloy before and after cryogenic treatment at different applied load and time were measured by nanoindention technique, and the products were also characterized by optical microscope. The results show that cryogenic treatment can refine the grains, and reduce creep deformation of the alloy, which can improve the creep resistant properties of Cu-11.74Al-0.38Ni alloy effectively.

Room-temperature creep deformation of cubic ZnS crystals under controlled light conditions

2020 ◽  
Vol 195 ◽  
pp. 690-697 ◽  
Author(s):  
Yu Oshima ◽  
Atsutomo Nakamura ◽  
K.Peter D. Lagerlöf ◽  
Tatsuya Yokoi ◽  
Katsuyuki Matsunaga
Keyword(s):  
Creep Deformation ◽  
Room Temperature ◽  
Light Conditions ◽  
Temperature Creep ◽  
Room Temperature Creep

Room Temperature Creep Behaviour of Pipeline Steels and Its Influence on Stress Corrosion Cracking

2002 ◽  
Author(s):  
Weixing Chen ◽  
Sheng-Hui Wang
Keyword(s):  
Cyclic Loading ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Creep Deformation ◽  
Room Temperature ◽  
Creep Behaviour ◽  
Corrosion Cracking ◽  
Pipeline Steels ◽  
Temperature Creep ◽  
Room Temperature Creep

Room temperature creep is often of significant importance in structural materials. Its occurrence, for example, may be an important factor contributing to crack growth during stress corrosion cracking. For pipeline steels used in gas transmission, room temperature creep deformation near the crack tip may result in a time dependent crack growth. In this research, room temperature creep of two pipeline steels with different grades was studied under various loading conditions including pure static, pure cyclic and a combination of static and cyclic loading. The creep deformation under a stress higher than the yield strength may represent the deformation behaviour at the crack tip. Due to cyclic hardening, all the steels crept at a stress higher than the yield strength exhibit cyclic creep retardation, which is less pronounced at lower stress-ratio (minimum stress/maximum stress). Pre-cyclic loading has significant effect on subsequent static creep. In general, pre-cyclic loading causes a burst of creep deformation under subsequent static loading, which may result in significantly larger cumulative creep strain than that of pure static creep depending on the initial loading strain and the number of cycles in pre-cyclic loading. The burst in creep deformation requires an incubation period that increases with number of prior load cycles. The burst strain is dependent on the number of cycles of prior cyclic loading in a more complicated manner. The implication of the creep behaviour observed in these tests is also discussed in terms of stress corrosion cracking in the pipeline steels.

scholarly journals The Strain Rate Sensitivity and Creep Behavior for the Tripler Plane of Potassium Dihydrogen Phosphate Crystal by Nanoindentation

Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 369
Author(s):  
Jianhui Mao ◽  
Wenjun Liu ◽  
Dongfang Li ◽  
Chenkai Zhang ◽  
Yi Ma
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Creep Deformation ◽  
Potassium Dihydrogen Phosphate ◽  
Rate Sensitivity ◽  
Dislocation Nucleation ◽  
Machining Process ◽  
Dihydrogen Phosphate ◽  
Potassium Dihydrogen ◽  
Kdp Crystals

As an excellent multifunctional single crystal, potassium dihydrogen phosphate (KDP) is a well-known, difficult-to-process material for its soft-brittle and deliquescent nature. The surface mechanical properties are critical to the machining process; however, the characteristics of deformation behavior for KDP crystals have not been well studied. In this work, the strain rate effect on hardness was investigated on the mechanically polished tripler plane of a KDP crystal relying on nanoindentation technology. By increasing the strain rate from 0.001 to 0.1 s−1, hardness increased from 1.67 to 2.07 GPa. Hence, the strain rate sensitivity was determined as 0.053, and the activation volume of dislocation nucleation was 169 Å3. Based on the constant load-holding method, creep deformation was studied at various holding depths at room temperature. Under the spherical tip, creep deformation could be greatly enhanced with increasing holding depth, which was mainly due to the enlarged holding strain. Under the self-similar Berkovich indenter, creep strain could be reduced at a deeper location. Such an indentation size effect on creep deformation was firstly reported for KDP crystals. The strain rate sensitivity of the steady-state creep flow was estimated, and the creep mechanism was qualitatively discussed.

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