The influence of strain rate and strain ageing on the flow stress of commercially-pure aluminium

1967 ◽  
Vol 15 (1) ◽  
pp. 47-62 ◽  
Author(s):  
A. Rosen ◽  
S.R. Bodner
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Pure Aluminium ◽  
Strain Ageing ◽  
Commercially Pure

Superplasticity in Coarse-Grained Al-Mg Alloys

2006 ◽  
Vol 519-521 ◽  
pp. 1285-1290 ◽  
Author(s):  
Ehab Samuel ◽  
John J. Jonas ◽  
F.H. Samuel ◽  
S.R. MacEwen
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Mg Alloys ◽  
Coarse Grained ◽  
High Temperature Deformation ◽  
Dynamic Strain ◽  
Temperature Deformation ◽  
Dynamic Strain Ageing ◽  
Strain Ageing ◽  
Al Mg Alloys

Superplasticity refers to a high temperature deformation process involving a marked sensitivity of the flow stress to the imposed strain rate, with resulting enhanced ductility. Although conventionally associated with fine-grained materials, superplasticity has recently been observed in coarse-grained alloys. The present research involves the deformation behavior of Al-Mg base alloys, where superpure Al-3%Mg and Al-5%Mg, and commercial Al 5056 were selected for study. The results for the Al-5%Mg and Al 5056 alloys are presented in this article. Flat sheet-type samples were tensile tested to 10% strain at increasing temperatures and at prescribed strain rates (0.001/s, 0.01/s, and 0.1/s). The dependence of flow stress on temperature was found to display some unusual characteristics. This behavior is interpreted as resulting from the occurrence of dynamic strain ageing (DSA). The aim of the overall study is to determine the relation between DSA and superplasticity in coarse-grained Al-Mg alloys. This will, in turn, lead to the control of the strain ageing behavior so as to produce the largest possible values of strain rate sensitivity (and, hence, elongation).

Experiments on Strain Rate History and Temperature Effects During the Plastic Deformation of Close-Packed Metals

1978 ◽  
Vol 45 (1) ◽  
pp. 60-66 ◽  
Author(s):  
P. E. Senseny ◽  
J. Duffy ◽  
R. H. Hawley
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Constant Strain Rate ◽  
Strain Rates ◽  
Stress Strain ◽  
Pure Zinc ◽  
Polycrystalline Metals ◽  
Commercially Pure ◽  
The Difference ◽  
Incremental Strain

A study is presented on the influence of strain rate and strain rate history on the flow stress of several metals. Experiments were performed on specimens of four polycrystalline metals: 1100-0 aluminum, OFHC copper, AZ31 B magnesium, and commercially pure zinc. The experiments involve, the use of a modified Kolsky bar to increase abruptly the imposed strain rate, initially 2 × 10−4 s−1, by a factor of more than 106. Tests were performed at selected temperatures in the range T ≤ (1/2)Tm. The results include complete stress-strain curves for deformation at constant strain rates as well as for deformation involving a sharp increment in strain rate. The difference in flow stress at a given value of strain for stress-strain curves obtained at constant but different strain rates provides one measure of the influence of strain rate on the flow stress. However, the results of the incremental strain rate experiments show that both strain rate and strain rate history contribute to this difference in flow stress. Hence, interpretation of both the incremental and the constant strain rate tests offers a means for distinguishing between the effects of strain rate as opposed to those of differences in strain rate history.

Effect of strain rate on low-endurance torsional fatigue in commercially pure aluminium

1968 ◽  
Vol 3 (4) ◽  
pp. 273-280 ◽  
Author(s):  
K J Miller ◽  
M N Rizk
Keyword(s):  
Strain Rate ◽  
Constant Strain Rate ◽  
Cyclic Hardening ◽  
Cyclic Softening ◽  
Pure Aluminium ◽  
Constant Torque ◽  
Torsional Fatigue ◽  
Commercially Pure ◽  
Strain And Strain Rate ◽  
Cumulative Strain

Commercially pure (99 per cent) aluminium has been subjected to high-strain low-endurance torsional fatigue under conditions of constant strain rate. (In this paper ‘strain’ and ‘strain rate’ refer to conditions at the surface of the specimen and therefore apply to the zones in which cracks are initiated.) Tests were performed at 20°C (0.315TM) and were controlled between constant torque limits of equal but reversed magnitudes. Below a critical strain rate, ·λcrit, the fatigue life obeys the law Nf = A·λm for a constant torque range. When ·λ exceeds ·λcrit, there is no significant strain-rate effect on fatigue endurance. It is suggested that cyclically activated creep mechanisms cause significant damage at strain rates less than 2Tcrit. A relaxation behaviour was observed after the first quarter cycle when torque ranges were greater than a critical level of 2 Tcrit. A similar phenomenon was observed at ranges less than 2 Tcrit with straining rates less than 2Tcrit but only when the specimens were close to failure and the initial cyclic hardening had been removed by cyclic softening. In consequence fatigue endurances were found to be less sensitive to torque at ranges greater than 2 Tcrit. Cumulative strain (cyclically induced creep) occurred at all torque ranges and straining rates. Minimum cumulative strains occurred at a torque range of 2 Tcrit with the value of Tcrit having a minimal dependence on the straining rate. The ratio of time to cyclic-dependent processes that contribute to failure is itself dependent on both the torque range and the straining rate. However, a single curve suffices to represent all results if a total strain path to failure criterion is adopted.

Dynamic Recrystallization Behavior of Pure Titanium

2014 ◽  
Vol 852 ◽  
pp. 66-70 ◽  
Author(s):  
Juan Hua Su ◽  
Ya Wei Han ◽  
Feng Zhang Ren ◽  
Zhi Qiang Chen
Keyword(s):  
Flow Stress ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
True Strain ◽  
Pure Titanium ◽  
Avrami Equation ◽  
Test Machine ◽  
Commercially Pure Titanium ◽  
Compression Tests ◽  
Commercially Pure

The dynamic recrystallization of commercially pure titanium was investigated by compression tests on Gleeble-1500D thermal simulation test machine at temperature of 700950 °C and strain rate of 0. 015 s1. The total compression deformation is 0.7(true strain). The kinetics of dynamic recrystallization of commercially pure titanium at 950 °C was modeled by Avrami equation. The results show that the dynamic recovery and recrystallization obviously occur during compression. The flow stress increases to a peak value and gradually decreases to a steady state. The flow stress is decreased with the increase of deformation temperature and it is increased with the increase of strain rate. The Avrami kinetics model of dynamic recrystallization of commercially pure titanium at 950 °C is obtained .

scholarly journals Hot Workability of 300M Steel Investigated by In Situ and Ex Situ Compression Tests

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 880 ◽  
Author(s):  
Rongchuang Chen ◽  
Haifeng Xiao ◽  
Min Wang ◽  
Jianjun Li
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Hot Working ◽  
Ex Situ ◽  
Lower Strain Rate ◽  
Hot Workability ◽  
Compression Tests ◽  
300M Steel ◽  
Lower Strain

In this work, hot compression experiments of 300M steel were performed at 900–1150 °C and 0.01–10 s−1. The relation of flow stress and microstructure evolution was analyzed. The intriguing finding was that at a lower strain rate (0.01 s−1), the flow stress curves were single-peaked, while at a higher strain rate (10 s−1), no peak occurred. Metallographic observation results revealed the phenomenon was because dynamic recrystallization was more complete at a lower strain rate. In situ compression tests were carried out to compare with the results by ex situ compression tests. Hot working maps representing the influences of strains, strain rates, and temperatures were established. It was found that the power dissipation coefficient was not only related to the recrystallized grain size but was also related to the volume fraction of recrystallized grains. The optimal hot working parameters were suggested. This work provides comprehensive understanding of the hot workability of 300M steel in thermal compression.

A Modified Peric Model for Al-Mg Alloy Sheet with Rate-Independent Initial Yield Stress at Warm Temperatures

2019 ◽  
Vol 287 ◽  
pp. 3-7
Author(s):  
Yong Zhang ◽  
Qing Zhang ◽  
Yuan Tao Sun ◽  
Xian Rong Qin
Keyword(s):  
Flow Stress ◽  
Plastic Strain ◽  
Strain Rate ◽  
Yield Stress ◽  
Constitutive Models ◽  
Mg Alloy ◽  
Initial Yield Stress ◽  
Initial Yield ◽  
Rate Dependent ◽  
Dependent Flow

The constitutive modeling of aluminum alloy under warm forming conditions generally considers the influence of temperature and strain rate. It has been shown by published flow stress curves of Al-Mg alloy that there is nearly no effect of strain rate on initial yield stress at various temperatures. However, most constitutive models ignored this phenomenon and may lead to inaccurate description. In order to capture the rate-independent initial yield stress, Peric model is modified via introducing plastic strain to multiply the strain rate, for eliminating the effect of strain rate when the plastic strain is zero. Other constitutive models including the Wagoner, modified Hockett–Sherby and Peric are also considered and compared. The results show that the modified Peric model could not only describe the temperature-and rate-dependent flow stress, but also capture the rate-independent initial yield stress, while the Wagoner, modified Hockett–Sherby and Peric model can only describe the temperature-and rate-dependent flow stress. Moreover, the modified Peric model could obtain proper static yield stress more naturally, and this property may have potential applications in rate-dependent simulations.

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