An investigation of the creep processes in tin and aluminum using a depth-sensing indentation technique

1992 ◽  
Vol 7 (3) ◽  
pp. 627-638 ◽  
Author(s):  
V. Raman ◽  
R. Berriche
Keyword(s):  
Stress Exponent ◽  
Constant Load ◽  
Indentation Creep ◽  
Depth Sensing ◽  
Creep Tests ◽  
Si Substrates ◽  
Uniaxial Creep ◽  
Rate Versus ◽  
Deformation Properties ◽  
Film Substrate

Constant load creep experiments were conducted using a depth-sensing indentation instrument with indentation depths in the submicron range. Experiments were conducted on polycrystalline Sn and sputtered Al films on Si substrates. The results show that the plastic depth versus time curves and the strain rate versus stress plots from these experiments are analogous to those obtained from conventional creep experiments using bulk specimens. The value of the stress exponent for Sn is close to the reported values from uniaxial creep tests. Tests on Al films showed that the stress exponent is dependent on the indentation depth and is governed by the proximity to the film/substrate interface. Load change experiments were also performed and the data from these tests were analyzed. It is concluded that indentation creep experiments may be useful in elucidating the deformation properties of materials and in identifying deformation mechanisms.

scholarly journals Nanoindentation Studies of Plasticity and Dislocation Creep in Halite

Geosciences ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 79 ◽  
Author(s):  
Christopher Thom ◽  
David Goldsby
Keyword(s):  
Strain Rate ◽  
Stress Exponent ◽  
Creep Behavior ◽  
Constant Load ◽  
Dislocation Creep ◽  
Indentation Creep ◽  
Creep Tests ◽  
Creep Flow ◽  
A Value ◽  
Flow Laws

Previous deformation experiments on halite have collectively explored different creep mechanisms, including dislocation creep and pressure solution. Here, we use an alternative to conventional uniaxial or triaxial deformation experiments—nanoindentation tests—to measure the hardness and creep behavior of single crystals of halite at room temperature. The hardness tests reveal two key phenomena: (1) strain rate-dependent hardness characterized by a value of the stress exponent of ~25, and (2) an indentation size effect, whereby hardness decreases with increasing size of the indents. Indentation creep tests were performed for hold times ranging from 3600 to 106 s, with a constant load of 100 mN. For hold times longer than 3 × 104 s, a transition from plasticity to power-law creep is observed as the stress decreases during the hold, with the latter characterized by a value of the stress exponent of 4.87 ± 0.91. An existing theoretical analysis allows us to directly compare our indentation creep data with dislocation creep flow laws for halite derived from triaxial experiments on polycrystalline samples. Using this analysis, we show an excellent agreement between our data and the flow laws, with the strain rate at a given stress varying by less than 5% for a commonly used flow law. Our results underscore the utility of using nanoindentation as an alternative to more conventional methods to measure the creep behavior of geological materials.

Computational and Experimental Characterization of Indentation Creep

2003 ◽  
Vol 795 ◽  
Author(s):  
Ming Dao ◽  
Hidenari Takagi ◽  
Masami Fujiwara ◽  
Masahisa Otsuka
Keyword(s):  
Finite Element ◽  
Power Law ◽  
Constant Load ◽  
Dislocation Creep ◽  
Solid Solution Alloy ◽  
Indentation Creep ◽  
Creep Tests ◽  
Uniaxial Creep ◽  
Self Similar ◽  
Power Law Creep

ABSTRACT:Detailed finite-element computations and carefully designed indentation creep experiments were carried out in order to establish a robust and systematic method to accurately extract creep properties during indentation creep tests. Finite-element simulations confirmed that, for a power law creep material, the indentation creep strain field is indeed self-similar in a constant-load indentation creep test, except during short transient periods at the initial loading stage and when there is a deformation mechanism change. Self-similar indentation creep leads to a constitutive equation from which the power-law creep exponent, n, the activation energy for creep, Qc and so on can be evaluated robustly. Samples made from an Al-5.3mol%Mg solid solution alloy were tested at temperatures ranging from 573 K to 773 K. The results are in good agreement with those obtained from conventional uniaxial creep tests in the dislocation creep regime.

scholarly journals Nanoindentation creep testing: Advantages and limitations of the constant contact pressure method

2021 ◽  
Author(s):  
Christian Minnert ◽  
Karsten Durst
Keyword(s):  
Contact Pressure ◽  
Constant Load ◽  
Indentation Creep ◽  
Creep Tests ◽  
Creep Properties ◽  
Pressure Method ◽  
Ultrafine Grained ◽  
Uniaxial Creep ◽  
Power Law Exponent ◽  
Properties Of Materials

AbstractDifferent loading protocols have been developed in the past to investigate the creep properties of materials using instrumented indentation testing technique. Recently, a new indentation creep method was presented, in which the contact pressure is kept constant during the creep test segment, similar to the constant stress applied in a uniaxial creep experiment. In this study, the results of constant contact pressure creep tests are compared to uniaxial and constant load hold indentation creep experiments on ultrafine grained Cu and CuAl5. The constant contact pressure method yields similar stress exponents as the uniaxial tests, down to indentation strain rates of 10–6 s−1, whereas the constant load hold method results mainly in a relaxation of the material at decreasing applied pressures. Furthermore, a pronounced change in the power law exponent at large stress reductions is found for both uniaxial and constant contact pressure tests, indicating a change in deformation mechanism of ultrafine grained metals. Graphical abstract

Time Dependent Deformation During Indentation Testing

1996 ◽  
Vol 436 ◽  
Author(s):  
B. N. Lucas ◽  
W. C. Oliver ◽  
G. M. Pharr ◽  
J-L. Loubet
Keyword(s):  
Loading Rate ◽  
Time History ◽  
Tensile Tests ◽  
Constant Load ◽  
Indentation Creep ◽  
Creep Tests ◽  
Constant Rate ◽  
Indentation Tests ◽  
Constant Loading Rate ◽  
Indentation Strain

AbstractConstant loading rate/load indentation tests (1/P dP/dt) and constant rate of loading followed by constant load (CRL/Hold) indentation creep tests have been conducted on high purity electropolished indium. It is shown that for a material with a constant hardness as a function of depth, a constant (1/P dP/dt) load-time history results in a constant indentation strain rate (1/h dh/dt). The results of the two types of tests are discussed and compared to data in the literature for constant stress tensile tests. The results from the constant (1/P dP/dt) experiments appear to give the best correlation to steady-state uniaxial data.

Effect of Grain Orientation on Indentation Induced Creep in Pure Zinc

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Aditya Gokhale ◽  
R. Sarvesha ◽  
Rajesh Prasad ◽  
Sudhanshu S. Singh ◽  
Jayant Jain
Keyword(s):  
Atomic Force Microscope ◽  
Stress Exponent ◽  
Grain Orientation ◽  
Indentation Creep ◽  
Creep Tests ◽  
Pure Zinc ◽  
Creep Response ◽  
Atomic Force ◽  
Pile Up ◽  
Anisotropic Creep

Abstract The study presents the anisotropy in the indentation creep response of zinc. Indentation creep tests were conducted on grains with three different orientations, namely, 〈0001〉, ⟨112¯0⟩, and ⟨101¯0⟩. Indentation creep along the 〈c〉 axis showed a pronounced creep exhibiting a 25% higher creep displacement as compared with indentation perpendicular to the 〈c〉 axis. However, the recovery observed was the highest for basal-oriented grains wherein a recovery of 50% to its indented depth was observed, whereas for ⟨112¯0⟩ the recovery observed was 30%. The stress exponent, n, was obtained by employing two different approaches for each of the orientations and a difference in the stress exponent value was also observed, highlighting the anisotropic creep response. Basal and non-basal oriented grains showed a lower (n ≅ 1.6) and higher stress exponent (n ≅ 5), respectively, highlighting the different operable creep mechanism. Surface topography using atomic force microscope (AFM) revealed twinning and sink-in for ⟨112¯0⟩ and ⟨101¯0⟩, whereas uniform pile up was observed for basal grain.

Graded Creep Deformation Properties of 316H Welds and its Impact on Creep

2018 ◽  
Author(s):  
S. Dey ◽  
D. M. Knowles ◽  
C. E. Truman
Keyword(s):  
Stress Distribution ◽  
Base Metal ◽  
Creep Deformation ◽  
Creep Damage ◽  
Impression Creep ◽  
Uniform Stress ◽  
Creep Tests ◽  
Creep Ductility ◽  
Uniaxial Creep ◽  
Deformation Properties

The creep damage evolution in multi-pass welds is believed to be influenced by the variation of creep rates from the weld to the base metal and through the HAZ. Material heterogeneity in a multi-pass weld leads to a non-uniform stress distribution resulting in non-uniform evolution of creep strains with strain localisation. Also, a non-uniform stress distribution may lead to highly multiaxial stress states in the weld resulting in a lower creep ductility. Since creep damage in metallic components is influenced by creep strain rate and creep ductility of the material amongst other factors, creep inhomogeneity in a weldment may significantly affect creep damage accumulation. Therefore, in order to predict creep behaviour of a multi-pass weld, it is important to take into account the gradation of creep deformation properties through the weld HAZ. Impression creep tests are useful in revealing localised creep properties in a material, where test results can be directly correlated to uniaxial creep tests. In this paper, a 2D finite element model of a multipass 316H weld with three different material sections (weld, HAZ, parent) is used to demonstrate the effects of creep deformation mismatch on stress and strain distributions. The paper also describes a series of impression creep tests planned and being conducted on an ex-service 316H weldment from a power plant steam generator with specimens taken from locations in the HAZ and at varying proximities to the weld fusion line. One specimen from the far away base metal and one from the weld centerline were also taken to serve as reference since the uniaxial creep deformation properties for the weld and the base material are known from uniaxial creep tests. By comparing the minimum creep rates for the HAZ specimens against the reference specimens from the weld and the base metal, Norton’s law creep coefficients and stress exponents will be derived for the HAZ specimens thereby revealing the gradation of creep deformation properties as a function of distance from the weld fusion line.

Creep Properties of a High Niobium Containing γ-TiAl Alloy Sheet Material

2002 ◽  
Vol 753 ◽  
Author(s):  
A. Bartels ◽  
S. Bystrzanowski ◽  
R. Gerling ◽  
F.-P. Schimansky ◽  
H. Kestler ◽  
...  
Keyword(s):  
Activation Energy ◽  
Stress Exponent ◽  
Elevated Temperatures ◽  
Sheet Material ◽  
Rolling Direction ◽  
Constant Load ◽  
Alloy Sheet ◽  
Tensile Creep ◽  
Creep Tests ◽  
Fine Grained

ABSTRACTIn this study Ti-46Al-9Nb (at%) sheet material processed by a powder metallurgical route was examined. Subsequent to hot rolling the sheets were subjected to a stress-relief treatment at 1273K for 3 hours. During this heat treatment a fine-grained near gamma microstructure has been formed. 100 hours tensile creep tests under constant load were carried out at 700°C in rolling direction, transverse direction as well as 45° direction. Using the method of load changes a stress exponent of 4.1 was determined. Furthermore, the apparent activation energy was determined in the temperature range of 715 – 775°C. Both stress exponent and activation energy suggest that diffusion assisted dislocation climb is the dominant creep mode. A comparison of these results with those of so-called conventional or so-called “2nd generation” γ-TiAl based alloys, e.g. Ti-46.5Al-4(Cr,Nb,Ta,B) (at%) and Ti-47Al-4(Cr,Mn,Nb,Si,B) (at%), indicates a significantly better creep resistance and a higher activation energy of the high Nb containing alloy. Additionally, internal friction experiments were conducted in order to analyze the deformation behavior under very small strains at elevated temperatures.

Effect of Tempering on Microstructure and Creep Properties of P911 Steel

2016 ◽  
Vol 879 ◽  
pp. 1963-1968 ◽  
Author(s):  
Evgeniy Tkachev ◽  
Marina Odnobokova ◽  
Alla Kipelova ◽  
Andrey Belyakov ◽  
Rustam Kaibyshev
Keyword(s):  
Creep Rate ◽  
Average Length ◽  
Load Condition ◽  
Constant Load ◽  
Creep Tests ◽  
Long Term Conditions ◽  
Creep Properties ◽  
Rate Versus ◽  
Mean Size ◽  
Lath Structure

The microstructure and creep properties of a P911-type steel normalized at 1060°C and then subjected to one-step tempering at 760°C for 3 h or two-step tempering at 300°C for 3 h + 760°C for 3 h were examined. The transmission electron microscope (TEM) observations showed that the tempered martensite lath structure (TMLS) with a lath thickness of 340 nm evolved after both tempering regimes. High dislocation densities of 3×1014 or 5×1014 m-2 retained after one-and two-step tempering respectively. M23C6 carbides with a mean size of 120 nm and V-rich MX carbonitrides having a “wing” shape with an average length of about 40 nm precipitated on high-and low-angle boundaries and within ferritic matrix, respectively. A number of Nb-rich M(C,N) carbonitrides with a mean size of 20 nm precipitated on dislocations during low temperature tempering. The creep tests were carried out under constant load condition at 650°С at applied stresses of 100 and 118 MPa. Analysis of creep rate versus time curves showed that the use of two-step tempering decreases the minimum creep rate providing an increase in the creep strength in long-term conditions.

scholarly journals High Temperature Creep Behaviour of Cast Nickel-Based Superalloys INC 713 LC, B1914 and MAR-M247

Metals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 152
Author(s):  
Marie Kvapilova ◽  
Petr Kral ◽  
Jiri Dvorak ◽  
Vaclav Sklenicka
Keyword(s):  
High Temperature ◽  
Stress Exponent ◽  
Creep Deformation ◽  
Creep Behaviour ◽  
Constant Load ◽  
Strength Properties ◽  
Creep Tests ◽  
Creep Properties ◽  
High Temperature Components ◽  
High Level

Cast nickel-based superalloys INC713 LC, B1914 and MAR-M247 are widely used for high temperature components in the aerospace, automotive and power industries due to their good castability, high level of strength properties at high temperature and hot corrosion resistance. The present study is focused on the mutual comparison of the creep properties of the above-mentioned superalloys, their creep and fracture behaviour and the identification of creep deformation mechanism(s). Standard constant load uniaxial creep tests were carried out up to the rupture at applied stress ranging from 150 to 700 MPa and temperatures of 800–1000 °C. The experimentally determined values of the stress exponent of the minimum creep rate, n, were rationalized by considering the existence of the threshold stress, σ0. The corrected values of the stress exponent correspond to the power-law creep regime and suggest dislocation climb and glide as dominating creep deformation mechanisms. Fractographic observations clearly indicate that the creep fracture is a brittle mostly mixed transgranular and intergranular mode, resulting in relatively low values of fracture strain. Determined main creep parameters show that the superalloy MAR-M247 exhibits the best creep properties, followed by B1914 and then the superalloy INC713 LC. However, that each of the investigated superalloys can be successfully used for high temperature components fulfils the required service loading conditions.

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