Deformation mechanisms of Al0.1CoCrFeNi at elevated temperatures
Tengfei YangZhi TangXie XieRobert E. CarrollGongyao WangYugang WangKarin A. DahmenPeter K. LiawYanwen Zhang
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Keywords:
Necking
Work hardening
Elongation
High-Entropy Alloys
Percent elongation of ductile metal in uniaxial tension due to non-homogeneity was analyzed based on gradient-dependent plasticity. Three assumptions are used to get the analytical solution of percent elongation: one is static equilibrium condition in axial direction; another is that plastic volumetric strain is zero in necking zone; the other is that the diameter in unloading zone remains constant after strain localization is initiated. The strain gradient term was introduced into the yield function of classical plastic mechanics to obtain the analytical solution of distributed plastic strain. Integrating the plastic strain and considering the influence of necking on plastic elongation, a one-dimensional analytical solution of percent elongation was proposed. The analytical solution shows that the percent elongation is inversely proportional to the gauge length, and the solution is formally similar to earlier empirical formula proposed by Barba. Comparisons of existing experimental results and present analytical solutions for relation between load and total elongation and for relation between percent elongation and gauge length were carried out and the new mechanical model for percent elongation was verified. Moreover, higher ductility, toughness and heterogeneity can cause much larger percentage elongation, which coincides with usual viewpoints.
Necking
Elongation
Tension (geology)
Ductility (Earth science)
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Necking
Superplasticity
Work hardening
Flow stress
Brittleness
Strain hardening exponent
Elongation
Titanium alloy
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A detailed study of room temperature mechanical behavior of B2-ordered Fe3Alsingle crystals had been conducted. It was found that the yield strength, plastic elongation and work-hardening rate were changed with orientations. The highest ductility was measured from the specimen with the orientation near [110], where the plastic elongation is 42%. In contrast, at near [100] the plastic elongation is only 14.1%. The high work-hardening rate of the orientation near [110] was confirmed to be the results of superdislocation interaction, and the dissociation of two-fold superdislocations into single dislocations led to cross-slip, which resulted in further increase in elongation. The low work-hardening rate of near [211] was due to single active slip system and the superdislocations kept two-fold until the specimen was fractured.
Elongation
Work hardening
Strain hardening exponent
Ductility (Earth science)
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Percent elongation of ductile metal in uniaxial tension due to non-homogeneity was analyzed based on gradient-dependent plasticity. Three assumptions are used to get the analytical solution of percent elongation: one is static equilibrium condition in axial direction; another is that plastic volumetric strain is zero in necking zone;the other is that the diameter in unloading zone remains constant after strain localization is initiated. The strain gradient term was introduced into the yield function of classical plastic mechanics to obtain the analytical solution of distributed plastic strain. Integrating the plastic strain and considering the influence of necking on plastic elongation, a one-dimensional analytical solution of percent elongation was proposed. The analytical solution shows that the percent elongation is inversely proportional to the gauge length, and the solution is formally similar to earlier empirical formula proposed by Barba. Comparisons of existing experimental results and present analytical solutions for relation between load and total elongation and for relation between percent elongation and gauge lengthwere carried out and the new mechanical model for percent elongation was verified. Moreover, higher ductility,toughness and heterogeneity can cause much larger percentage elongation, which coincides with usual viewpoints.
Necking
Elongation
Tension (geology)
Ductility (Earth science)
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Work hardening
Deformation mechanism
Strain hardening exponent
Hardening (computing)
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Necking behaviour in tensile tests has been investigated for typical steel sheets. Local elongation in spontaneously necked region depends mainly upon the strain diffusibility of materials. Using specimens having artificial necking, a fomula describing this strain diffusibility has experimentally been deduced in relation to temperature and strain rate dependences of flow stress, and stress ratio. Furthermore, the relationship between necking elongation and macro-factors affecting it is formulated as follows, δn∝ΔP/P+0.22r/r+1where, δn : necking elongation, P: maximum load, ΔP : increment of maximum load with the change in tension speed from 10 mm/min to 100 mm/min, r: Lankford value in tensile direction.
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Elongation
Tension (geology)
Strain (injury)
Tensile testing
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When a necking appears in a specimen under a tensile test, the strain rate at the necking region must become larger than the other region of the specimen. Generally, the flow stress of the material increases with strain rate. Taking these factors into account, the condition for the appearance of a nicking in a specimen was calculated. It was shown that a necking can not appear in a specimen if the size and the local work-hardening rate are ideally uniform in the specimen. The cause for the appearance of a necking in a real specimen is the inhomogeneities of the cross-sectional area or the local work-hardening rate in the specimen. Comparisons of the calculated results with experiments are described.
Necking
Work hardening
Tensile testing
Strain hardening exponent
Hardening (computing)
Flow stress
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A lot of research has been focused on the necking process during the plastic deformation of sheet metals, but the localized necking is rarely distinguished form diffused necking by experiments, due to the limit of measurement equipment and method. Quenching and Partitioning (Q&P) steel is a 3rd generation advanced high strength steel (AHSS). Its good combination of high strength and ductility ensures potential application in automobile industry. Uniaxial tensile tests of QP980 steel sheet at five strain rates are performed to investigate the necking process and the effect of strain rate on necking behavior of Q&P steel. Digital image correlation (DIC) method is applied during tensile tests, and evolutions of major strain, minor strain and normal strain distributions along gauge section of the tensile specimens are obtained. The diffused and localized necking strains are determined according to SWIFT necking theory and HILL necking theory respectively. The test results indicate that with the increasing of strain rate in the investigated range, the diffused necking strain decreases from 0.152 to 0.120 and localized necking strain decreases from 0.245 to 0.137. Meanwhile, the difference of the two strains decreases form 0.096 to 0.017. Thus it can be concluded that strain rate has an influence on both necking strains during the deformation of QP980 steel sheet. Diffused and localized necking strains are determined by uniaxial tensile tests with the aid of DIC technique and the effect of strain rate on necking strains is evaluated.
Necking
Tensile testing
Ductility (Earth science)
Strain (injury)
Digital image correlation
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Necking
Work hardening
Elongation
Flow stress
Bar (unit)
Strain hardening exponent
Hardening (computing)
Tensile testing
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The necking limit diagram NLD and the forming limit diagram FLD under the wide-range bi-axial tensile stress conditions were obtained by using various sheet metals of steels, Al-alloys and a copper. The good correlation between the limited strain values of NLD and FLD and the mechanical properties of total elongation and r-value etc. were obtained. Moreover, the strain dependency of the work hardening coefficient n-value in higher strain area was different according to each material. The complex value of n-value and r-value was defined as the equivalent work hardening coefficient neq-value in higher strain area. And when the neq-value was substituted to Gotoh's modeling of localized necking limited strain, FLD that accuracy is high was able to be predicted.
Necking
Forming limit diagram
Work hardening
Strain hardening exponent
Elongation
R-value (soils)
Hardening (computing)
Strain (injury)
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