Strain Rate Sensitivity of 31Mn-3Al-3Si TWIP Steel with Partially Recrystallized Fine Grained Structure

2008 ◽  
Vol 584-586 ◽  
pp. 673-678 ◽  
Author(s):  
Rintaro Ueji ◽  
Kenji Harada ◽  
Akihiko Takemura ◽  
Kazutoshi Kunishige
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Twip Steel ◽  
Volume Fraction ◽  
Tensile Deformation ◽  
Cell Structure ◽  
Rate Sensitivity ◽  
Dislocation Cell ◽  
Annealed Specimen ◽  
Deformation Behaviors

Strain rate sensitivity of the strength of TWIP (Twinning Induced Plasticity) steel with the mixture of recrystallized fine grains and rolling-deformation microstructures was studied. The 31mass%Mn-3%Al-3%Si TWIP steel sheet was severely cold-rolled to a reduction of 92% and subsequently annealed at various temperatures ranging from 600oC to 700oC in order to obtain the partial recrystallized microstructure with various fraction of recrystallized microstructure. The 600oC annealed specimen keeps similar morphologies as observed in the as-rolled structure consisting of both the fine lamellar dislocation cell structure and the twin/matrix lamellar structure; whereas, in the specimen annealed at 625oC or 675oC , the partially recrystallized fine grains (d~1µm) with a few dislocations evolve. The volume fraction of recrystallized fine grains increases with increasing of the annealing temperature while the mean diameter of the recrystallized grains is not changed largely. The tensile deformation behaviors were measured at various strain rates ranging from 10-3sec-1 to 102sec-1. The strength and elongation become smaller and larger, respectively, with increasing the fraction of the recrystallized microstructure. The activation volume of dislocations becomes larger with increasing the fraction of recrystallized microstructure.

SERRATION BEHAVIOR OF AA5182/POLYPROPYLENE/AA5182 SANDWICH SHEETS

2006 ◽  
Vol 20 (25n27) ◽  
pp. 4316-4321
Author(s):  
KEE JOO KIM ◽  
JOO SUNG KIM
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Volume Fraction ◽  
Tensile Deformation ◽  
Rate Sensitivity ◽  
High Volume ◽  
Thickness Variation ◽  
Sandwich Sheet ◽  
Serration Behavior ◽  
Sandwich Sheets

The examination of serration behavior has been made after the tensile deformation of the AA/PP/AA sandwich sheets as well as that of the 5182 aluminum skins. All sandwich sheets and the 5182 aluminum skin showed serration behavior on their flow curves. However, the magnitude of serration was significantly diminished in the sandwich sheet with high volume fraction of the polypropylene core. According to the results of the analysis of the surface roughness following the tensile test, Lüders band depth of the sandwich sheet evidently showed lower than that of the 5182 aluminum skin. The strain rate sensitivity, m-value, of the 5182 aluminum skin was -0.006. By attaching these skins to the polypropylene core, which has relatively large positive value of 0.050, m-value of the sandwich sheets changed to a positive value. The serration reduction of the sandwich sheets was quantitatively investigated with respect to the effect on polypropylene thickness variation, that on the strain rate sensitivity and that on the localized stress state. It was found that the serration reduction degree from the experimental results of the sandwich sheet was higher than from the calculated values by the rule of mixture based on the volume fraction of the skins and the core.

Bulge Test Characterization of Static Softening and Dynamic Instabilities in Foils of an Al-Based Alloy

2001 ◽  
Vol 695 ◽  
Author(s):  
Miroslav Cieslar ◽  
Ayatollah Karimi ◽  
Jean-Luc Martin
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Cell Structure ◽  
Rate Sensitivity ◽  
Bulge Test ◽  
Large Strains ◽  
Subgrain Structure ◽  
Free Standing ◽  
Strain Behavior ◽  
Bulge Testing

ABSTRACTEffects of recovery and recrystallization on subsequent stress – strain behavior were studied in foils of non-age hardenable Al based alloy. A bulge testing device for mechanical testing of thin free standing films and foils, enabling the detection of large strains, was employed. The bulge tester was used at RT both for the predeformation of the foil in the biaxial mode and also for the study of softening after subsequent one-step annealing. Three stages of strength drop as a function of the annealing temperature were observed between RT and 590°C. The contribution of different annealing processes to the softening was established using transmission electron microscopy. It was found that below 200°C only redistribution of dislocations inside dislocation cells and refinement of the cell structure occurred. Between 200°C and 380°C the formation of a subgrain structure was observed. The softening process is terminated as partial recrystallization takes place at higher annealing temperatures. Dynamic interaction of solutes with dislocations was revealed during prestraining as well as poststraining of foils. This effect resulted in the appearance of a negative strain rate sensitivity and dynamic instabilities after appropriate prestraining and annealing conditions. The above results show that bulge testing of Al foils allows to study the successive annealing stages by measuring the most important macroscopic parameters of plastic deformation (yield stress, work hardening rate, ductility, strain rate sensitivity, etc.). These stages could be related to the microstructure evolution.

The Effect of Controlled Melt-Solidification on the Strain Rate Sensitivity of a Squeeze-Cast Hybrid-Reinforced Aluminum AA 6061 Matrix Composite

2015 ◽  
Vol 16 ◽  
pp. 1-16
Author(s):  
B.O. Malomo ◽  
O.O. Fadodun ◽  
K.M. Oluwasegun ◽  
A.T. Ogunbodede ◽  
S.A. Ibitoye ◽  
...  
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Matrix Composite ◽  
Deformation Behavior ◽  
Squeeze Casting ◽  
Volume Fraction ◽  
Tensile Elongation ◽  
Testing Machine ◽  
Rate Sensitivity ◽  
Cooling Rates

A framework based on the relationship between variations in cooling rates and volume fraction of reinforcements during solidification processing to enhance the deformation behavior of aluminum alloy AA6061 matrix composite produced with a hybrid system of reinforcements is investigated in this study. The aluminum matrix composite with 5 %, 10 % and 20 % volume fraction of reinforcements (Al2O3-SiC) was synthesized by infiltrating molten aluminum AA 6061 at a pouring temperature of 740 °C into prefabricated preforms of reinforcements at a pressure of 80 MPa, die preheat temperature of 300 °C and pressure holding time of 15 s using the squeeze casting method. By employing water jet spraying at the rate of 0.1, 0.2 and 0.3 kg/s and taking measurements using a K-type thermocouple, cooling rates were obtained in correspondence with varying volume fractions of reinforcements. The developed composites were sectioned and microstructural features were examined by optical microscopy. Tensile testing was conducted according to ASTM B557 standard using an MTS testing machine. It was observed that cooling rates decreased as the volume fraction of reinforcements was increased and the cooling time also increased accordingly during this process. With respect to deformation behavior, higher cooling rates are associated with an improvement in mechanical properties at 5 % and 10 % additions of hybrid reinforcement particles but this effect diminishes as the volume fraction of reinforcements was increased to 20 %. Also, the strain rate sensitivity (SRS) exponent increased considerably with strain rates and volume fraction of reinforcements, but the tensile elongation values decreased with increasing volume fraction of reinforcements; and the variations in these properties were most significant for samples containing 20% volume fraction of hybrid reinforcements.From the foregoing, it follows that an experimentally-determined optimal solidification range is critical to the enhancement of deformation parameters as the volume fraction of reinforcements is varied in a squeeze casting process.

Enhanced Formability in Sheet Metals Produced by Cladding a High Strain-Rate Sensitive Layer

2013 ◽  
Vol 81 (2) ◽  
Author(s):  
X. H. Hu ◽  
P. D. Wu ◽  
D. J. Lloyd ◽  
J. D. Embury
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Volume Fraction ◽  
Rate Sensitivity ◽  
Core Material ◽  
Sensitive Layer ◽  
Element Analysis ◽  
Clad Sheet ◽  
Clad Layer ◽  
The One

The necking behavior of cladding sheets with a rate-sensitive layer cladding on a rate-insensitive core material has been studied. A nonlinear long-wavelength analysis, similar to the one proposed by Hutchinson and Neale (1977, “Influence of Strain-Rate Sensitivity on Necking Under Uniaxial Tension,” Acta Metal., 25, pp. 839–846) for monolithic rate-sensitive materials, is developed to identify the onset of necking in a rate-sensitive clad sheet. This relatively simple analysis is validated by comparing its numerical results with those based on more complicated finite element analysis. It is demonstrated that for monolithic rate-sensitive materials the proposed nonlinear analysis reduces to the one developed by Hutchinson and Neale (1977). For cladding sheets, it is found that the necking strain increases monotonically by increasing the strain-rate sensitivity of the clad layer if the volume fraction of cladding is fixed. It is also revealed that, for fixed strain-rate sensitivity of the clad layer, necking localization is retarded by increasing the volume fraction of the cladding layer.

Dynamic Tensile Properties of TiCp/Ti Composite

2008 ◽  
Vol 385-387 ◽  
pp. 873-876
Author(s):  
Fang Jiang ◽  
Dong Zhao ◽  
Jian Guo Ning
Keyword(s):  
Titanium Alloy ◽  
High Strain Rate ◽  
Strain Rate ◽  
Tensile Properties ◽  
Strain Rate Sensitivity ◽  
High Strain ◽  
Volume Fraction ◽  
Rate Sensitivity ◽  
The Matrix ◽  
High Strain Rate Sensitivity

The tensile properties of a titanium alloy reinforced with 3% by volume fraction of TiC particles and of an unreinforced titanium alloy are studied over a range of strain rates from 0.0001s-1 to 1300s-1 using quasi-static material testing system (MTS810) and split Hopkinson tensile bar apparatus. The experimental results show that both the TiCp/Ti composite and its matrix alloy exhibit an obvious strain-rate hardening property. But the high strain-rate sensitivity of the TiCp/Ti composite is significantly higher than that of the matrix. The high strain-rate sensitivity of the TiCp/Ti composite is considered to be originated from the high dislocation accumulation rate during dynamic deformation and the constraint of TiC particles on the surrounding matrix, which dramatically enhances rate of the matrix. Finally, a phenomenological dynamic constitutive relation is established considering the composite is elastic-perfectly plastic material.

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