Dynamic Deformation Behavior of ECAPed AZ31 Magnesium Alloy

2014 ◽  
Vol 566 ◽  
pp. 104-109
Author(s):  
Hai Tao Hu ◽  
Feng Zhao ◽  
Ying Gang Miao ◽  
Tao Suo ◽  
Qiong Deng ◽  
...  
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Strain Hardening ◽  
Grain Refinement ◽  
Rate Sensitivity ◽  
Dynamic Mechanical Properties ◽  
Angular Pressing ◽  
Fine Grain ◽  
Split Hopkinson ◽  
Dynamic Deformation Behavior

Equal channel angular pressing (ECAP) has been widely used for grain refinement in many alloys. In this article, the major emphasis was on the effect of grain size, temperature and strain rate on dynamic behavior of ECAPed AZ31. The dynamic mechanical properties of 6 pass and 8 pass ECAPed AZ31 were tested by split hopkinson pressing bar (SHPB) at wide temperatures range. At dynamic loading conditions, the ECAPed AZ31 shows strong strain hardening properties. The strain hardening rates decrease due to more slip systems’ opening with the increase of temperature. With the grain refinement, the fine-grain size and temperature show strong effect on the strain rate sensitivity.

Cavitation Behavior of Ultra-Fine Grained Ti-6Al-4V Alloy Produced by Equal-Channel Angular Pressing

2007 ◽  
Vol 551-552 ◽  
pp. 621-626
Author(s):  
Young Gun Ko ◽  
Yong Nam Kwon ◽  
Jung Hwan Lee ◽  
Dong Hyuk Shin ◽  
Chong Soo Lee
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Equal Channel Angular Pressing ◽  
Cavity Growth ◽  
Rate Sensitivity ◽  
Theoretical Models ◽  
Coarse Grained ◽  
Fine Grained ◽  
Angular Pressing ◽  
Cavitation Behavior

Cavitation behavior during superplastic flow of ultra-fine grained (UFG) Ti-6Al-4V alloy was established with the variation of grain size and misorientation. After imposing an effective strainup to 8 via equal-channel angular pressing (ECAP) at 873 K, alpha-phase grains were markedly refined from 11 μm to ≈ 0.3 μm, and misorientation angle was increased. Uniaxial-tension tests were conducted for initial coarse grained (CG) and two UFG alloys (ε = 4 and 8) at temperature of 973 K and strain rate of 10-4 s-1. Quantitative measurements of cavitation evidenced that both the average size and the area fraction of cavities significantly decreased with decreasing grain size and/or increasing misorientation. It was also found that, when compared to CG alloy, cavitation as well as diffused necking was less prevalent in UFG alloys, which was presumably due to the higher value of strain-rate sensitivity. Based on the several theoretical models describing the cavity growth behavior, the cavity growth mechanism in UFG alloys was suggested.

Grain Refinement during Superplastic Deformation of Coarse-Grained Al-Mg-Cu Alloys

2006 ◽  
Vol 509 ◽  
pp. 75-80 ◽  
Author(s):  
M.I. Cruz-Palacios ◽  
D. Hernández-Silva ◽  
L.A. Barrales-Mora ◽  
M.A. García-Bernal
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Grain Refinement ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Mg Alloy ◽  
Coarse Grained ◽  
Dislocation Creep ◽  
Rolled Plate ◽  
Strain Rates

In the present study the superplastic behavior of Al-6%Mg–0.5%Cu and Al–8%Mg– 0.5%Cu in a coarse grain size condition has been studied. The alloys are melted in an electrical furnace under argon atmosphere. The ingots (25 mm thick) are homogenized at 400 °C during 72 h and then rolled at 430 °C to a thickness of 5 mm. The mean grain size after rolling is 55 µm for the 6%Mg alloy and 61 µm for the 8%Mg alloy. Tensile test specimens are machined from the rolled plate in the rolling direction. Strain-rate-change tests at temperatures between 300 and 450 °C and strain rates between 1x10-4 and 1x10-1 s-1 are carried out to determine the strain rate sensitivity of the flow stress. Finally, elongation to failure tests are conducted at temperatures and strain rates where the alloys show a high strain rate sensitivity. Elongations higher than 390 % are obtained for the 8%Mg alloy. It is observed that the grip regions of the deformed samples show coarser grains than the regions near to the fracture surface. This means that grain refinement takes place during deformation, suggesting that the principal deformation mechanism is dislocation creep.

Effects of strain hardenability and strain-rate sensitivity on the plastic flow and deformation homogeneity during equal channel angular pressing

2001 ◽  
Vol 16 (3) ◽  
pp. 856-864 ◽  
Author(s):  
Hyoung Seop Kim ◽  
Sun Ig Hong ◽  
Min Hong Seo
Keyword(s):  
Strain Rate ◽  
Strain Hardening ◽  
Plastic Flow ◽  
Equal Channel Angular Pressing ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Strain Hardening Exponent ◽  
Angular Pressing ◽  
Deformation Inhomogeneity ◽  
Method Analysis

The effects of strain hardenability and strain rate sensitivity on the plastic flow and deformation inhomogeneity during equal channel angular pressing were studied using a finite element method analysis. In this study, perfect plastic nonhardening and rate-insensitive materials, and rate-sensitive materials were considered. In case of the nonhardening and rate-insensitive materials, the deformed geometry was predicted to be quite uniform and homogeneous. Deformation inhomogeneity developed, however, in materials with finite work-hardening exponent and strain-rate sensitivity. The corner gap formed in strain-hardening materials whereas the upper and lower channel gaps formed in strain-rate-sensitive materials. The deformation inhomogeneity was strongly dependent on the relative effects of strain-hardening exponent and strain-rate sensitivity. The predictions on the deformation inhomogeneity and the formation of corner and channel gaps were compatible with the experimental data published in the literature.

Strategy for Achieving High Strength in Al-Mg-Sc Alloys by Intense Plastic Straining

2012 ◽  
Vol 706-709 ◽  
pp. 55-60 ◽  
Author(s):  
Rustam Kaibyshev ◽  
Anna Mogucheva ◽  
Andrii Dubyna
Keyword(s):  
Grain Size ◽  
Strain Hardening ◽  
Grain Refinement ◽  
Equal Channel Angular Pressing ◽  
High Strength ◽  
Necessary Condition ◽  
Angular Pressing ◽  
Strength Increment ◽  
Hardened Condition

It is shown that implementation of high strains through equal-channel angular pressing (ECAP) and/or rolling into alloys belonging to Al-Mg-Sc-Zr system allows achieving high strength and satisfactory ductility. It was shown that strain hardening gives a main contribution to overall strength increment attributed to intense plastic straining; the role of grain size hardening is minor. However, extensive grain refinement is a necessary condition for retaining sufficient ductility in full-hardened condition for these materials.

Superplastic Properties of Hipped and Extruded Iron Carbide

1990 ◽  
Vol 196 ◽  
Author(s):  
W. J. Kim ◽  
O. A. Ruano ◽  
J. Wolfenstine ◽  
G. Frommeyer ◽  
O. D. Sherby
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Iron Carbide ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Strain Rate Range ◽  
Relative Strength ◽  
Compression Tests ◽  
Volume Percent ◽  
Fine Grain

ABSTRACTHipped and extruded materials were prepared from atomized-powders containing 5.25C, 1.5Cr and balance Fe. The materials consist of a matrix of 80 volume percent of iron carbide and 20 volume percent of a discontinous iron base phase. Both processed materials were reduced in thickness (6:1) at 720°C. The grain size was about 2 μm for the hipped-and-pressed material and about 4 μm for the extruded-and-pressed material. Compression tests were used to evaluate the strain-rate-sensitivity exponent, m, in the temperature range from 725°C to 950°C, over the strain rate range of 10−5 to 2 × 10−2 s−1. The as-hipped material does not exhibit superplastic behavior because the grain shape is not equiaxed. At low stresses, in the superplastic range (m≈0.5), the hipped-and-pressed material was weaker than the extruded-and-pressed material as a result of the fine grain size. At high stresses, when slip dominates the deformation process, m is about 0.2 and a reversal in the relative strength is obtained. Tensile tests were performed and elongations in excess of 600% were achieved. The hipped-and-pressed material was shown to be more ductile than the extruded-and pressed-material which is attributed to its fine grain size.

Measuring the strain rate sensitivity by instrumented indentation. Application to an ultrafine grain (equal channel angular–pressed) eutectic Sn–Bi alloy

2004 ◽  
Vol 19 (1) ◽  
pp. 282-290 ◽  
Author(s):  
J. Alkorta ◽  
J. Gil Sevillano
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
True Strain ◽  
Rate Sensitivity ◽  
Ultrafine Grain ◽  
Boundary Slip ◽  
True Strain Rate ◽  
Angular Pressing ◽  
Fine Grain

The ability of using nanoindentation raw data for characterizing the strain rate sensitivity of the flow stress of elastic–plastic materials has been assessed by finite element calculations. Correction factors for deducing the true strain rate sensitivity from the hardness sensitivity to the hardness penetration rate have been obtained for situations where the elastic contribution to the penetration is not negligible. The results of the analysis are applied to the experimental measurement by nanoindentation of the strain rate sensitivity of an ultrafine grain Sn–Bi eutectic processed by equal channel angular pressing. The flow stress of this material displays bilinear power-law strain-rate dependence. It is also shown that at very low indentation depths, discontinuities of the hardness–penetration curve of the fine-grain Sn–Bi can be correlated with local grain or interphase boundary slip events near the indentation.

Effect of ECAP Hot Processing on Grain Refinement and Superplasticity of 1933 Aluminium Alloy

2007 ◽  
Vol 551-552 ◽  
pp. 193-198
Author(s):  
Hong Zhen Guo ◽  
J. Zhao ◽  
S.C. Yuan ◽  
Z.L. Zhao ◽  
Ze Kun Yao
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Aluminium Alloy ◽  
Grain Refinement ◽  
Initial Strain Rate ◽  
Angular Pressing ◽  
Wide Range ◽  
Superplastic Elongation ◽  
Superplastic Properties ◽  
Metallic Grains

Cold and hot Equal-Channel Angular Pressing (ECAP) is an effective method to refine metallic grains. In this paper, superplastic properties of 1933 aluminium alloy were evaluated and the effect of hot ECAP on grain refinement and superplasticity was investigated. The testing results show that the refinement of grains can not be infinitely increased with the increasing of ECAP passes (or total strain). Under the isothermal ECAP conditions of the present study, optimum ECAP passes for 1933 alloy are 4 passes. The grain size of 1933 alloy was refined from 20~50μm to 7~12μm by means of ECAP for 4 passes at 300°C (route Bc), so its superplasticity was improved. Compared with original samples annealed at 400°C, the superplastic elongation of samples processed by ECAP for 4 passes increases by a factor of 130% about, and the range of superplastic temperature varies from 140°C to 210°C. The optimal superplastic temperature and initial strain rate is 510°C and 3.3×10-4s-1 individually, at which the elongation reaches 262% and the flow stress is 7.8MPa only. In a word, 1933 aluminium alloy can present more excellent superplasticity in wide range of superplastic temperature and strain rate.

Local Investigations of the Mechanical Properties of Ultrafine Grained Metals by Nanoindentations

2006 ◽  
Vol 503-504 ◽  
pp. 31-36 ◽  
Author(s):  
Johannes Mueller ◽  
Karsten Durst ◽  
Dorothea Amberger ◽  
Matthias Göken
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Room Temperature ◽  
Rate Sensitivity ◽  
Strain Rates ◽  
Fcc Metals ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Indentation Strain

The mechanical properties of ultrafine-grained metals processed by equal channel angular pressing is investigated by nanoindentations in comparison with measurements on nanocrystalline nickel with a grain size between 20 and 400 nm produced by pulsed electrodeposition. Besides hardness and Young’s modulus measurements, the nanoindentation method allows also controlled experiments on the strain rate sensitivity, which are discussed in detail in this paper. Nanoindentation measurements can be performed at indentation strain rates between 10-3 s-1 and 0.1 s-1. Nanocrystalline and ultrafine-grained fcc metals as Al and Ni show a significant strain rate sensitivity at room temperature in comparison with conventional grain sized materials. In ultrafine-grained bcc Fe the strain rate sensitivity does not change significantly after severe plastic deformation. Inelastic effects are found during repeated unloading-loading experiments in nanoindentations.

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