Effect of the Strain and Strain Rate on Microstructure Evolution and Superplastic Deformation Mechanisms

The hot deformation behavior and microstructure evolution of powder metallurgy (PM) Ti43Al9V0.3Y alloy with fine equiaxed γ and B2 grains were investigated using uniaxial hot compression. Its stress exponent and activation energy were 2.78 and 295.86 kJ/mol, respectively. The efficiency of power dissipation and instability parameters were evaluated, and processing maps at 50% and 80% strains were developed. It is demonstrated that the microstructure evolution was dependent on the temperature, strain, and strain rate. Both temperature and strain increases led to a decrease in the γ phase. Moreover, dynamic recrystallization (DRX) and grain boundary slip both played important roles in deformation. Reasonable parameters for secondary hot working included temperatures above 1100 °C but below 1200 °C with a strain rate of less than 1 s−1 at 80% strain. Suitable hot working parameters at 50% strain were 1150–1200 °C/≤1 s−1 and 1000–1200 °C/≤0.05 s−1.

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A Sigmoidal Model for Superplastic Deformation

Proceedings of the Institution of Mechanical Engineers Part L Journal of Materials Design and Applications ◽

10.1243/146442005x10355 ◽

2005 ◽

Vol 219 (3) ◽

pp. 149-162 ◽

Cited By ~ 1

Author(s):

W Pan ◽

M Krohn ◽

S B Leen ◽

T H Hyde ◽

S Walløe

Keyword(s):

Strain Rate ◽

Superplastic Deformation ◽

Model Performance ◽

Tensile Tests ◽

Deformation Analysis ◽

Rate Variation ◽

Strain And Strain Rate ◽

Sigmoidal Model ◽

Using Data ◽

Theoretical Analyses

A new phenomenological model, designed to capture the sigmoidal nature of stress dependency on strain rate for superplastic deformation, is presented. The model is developed for the Ti-6Al-2Sn-4Zr-2Mo alloy using data obtained under controlled strain-rate tensile tests spanning a range of strain rates and temperatures, from 930 to 980 °C. The sigmoidal model performance is compared with that of a more conventional double-power law, strain, and strain-rate hardening model using time-dependent finite element and theoretical analyses. The primary intended application of the sigmoidal model is for more accurate simulation of the effects of strain-rate variation within test specimens and sheet during superplastic deformation. Analysis of this variation within two designs of tensile test specimens is presented to illustrate this aspect.

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The high strain rate superplastic deformation mechanisms of mechanically alloyed aluminum IN90211

Materials Science and Engineering A ◽

10.1016/0921-5093(90)90225-r ◽

1990 ◽

Vol 128 (2) ◽

pp. 171-182 ◽

Cited By ~ 66

Author(s):

T.R. Bieler ◽

A.K. Mukherjee

Keyword(s):

High Strain Rate ◽

Strain Rate ◽

Superplastic Deformation ◽

High Strain ◽

Deformation Mechanisms ◽

Mechanically Alloyed

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Dynamic Mechanical Behavior and Microstructure Evolution of an Extruded 6013-T4 Alloy at Elevated Temperatures

Metals ◽

10.3390/met9060629 ◽

2019 ◽

Vol 9 (6) ◽

pp. 629 ◽

Cited By ~ 2

Author(s):

Tuo Ye ◽

Yuanzhi Wu ◽

Wei Liu ◽

Bin Deng ◽

Anmin Liu ◽

...

Keyword(s):

Mechanical Properties ◽

Strain Rate ◽

Stress Level ◽

Microstructure Evolution ◽

Elevated Temperatures ◽

Strain Rate Range ◽

Rate Range ◽

Dynamic Mechanical Behavior ◽

Strain And Strain Rate ◽

Increasing Temperature

The mechanical properties of an extruded 6013-T4 alloy were tested at a temperature range from 25 to 400 °C and strain rate range from 1 × 103 to 5 × 103 s−1. The results demonstrate that the stress level is sensitive to strain rate and temperature. The stress level increases slightly with increasing strain rate and decreases remarkably with increasing temperature. The dislocation and precipitate undergo great changes. When deformed at 25 °C, the density of the dislocation increases with strain and strain rate; which leads to a higher stress level. A great number of needle-like precipitates were observed at samples deformed at 200 °C. It is clear that the density of dislocation increases with strain and strain rate. When impacted at 400 °C, the coarser precipitates were found in the specimen; the density of the dislocation increases with strain and strain rate.

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The effects of strain and strain rate on residual microstructures in copper

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100143687 ◽

1986 ◽

Vol 44 ◽

pp. 420-421

Author(s):

M. F. Stevens ◽

P. S. Follansbee

Keyword(s):

Strain Rate ◽

Applied Stress ◽

Threshold Stress ◽

Rate Sensitivity ◽

Viscous Drag ◽

Strain Rates ◽

Strain And Strain Rate ◽

Threshold Strength ◽

Mechanism Transition ◽

Intrinsic Strength

The strain rate sensitivity of a variety of materials is known to increase rapidly at strain rates exceeding ∼103 sec-1. This transition has most often in the past been attributed to a transition from thermally activated guide to viscous drag control. An important condition for imposition of dislocation drag effects is that the applied stress, σ, must be on the order of or greater than the threshold stress, which is the flow stress at OK. From Fig. 1, it can be seen for OFE Cu that the ratio of the applied stress to threshold stress remains constant even at strain rates as high as 104 sec-1 suggesting that there is not a mechanism transition but that the intrinsic strength is increasing, since the threshold strength is a mechanical measure of intrinsic strength. These measurements were made at constant strain levels of 0.2, wnich is not a guarantee of constant microstructure. The increase in threshold stress at higher strain rates is a strong indication that the microstructural evolution is a function of strain rate and that the dependence becomes stronger at high strain rates.

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