Effects of dynamic strain ageing on the strain-rate sensitivity parameter ofα-zirconium

1987 ◽  
Vol 6 (6) ◽  
pp. 666-668 ◽  
Author(s):  
F. Povolo ◽  
G. H. Rubiolo
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Dynamic Strain ◽  
Dynamic Strain Ageing ◽  
Strain Ageing ◽  
Sensitivity Parameter

Dynamic Strain Aging during Tensile Deformation of Extruded AZ81 Magnesium Alloy

2013 ◽  
Vol 652-654 ◽  
pp. 1937-1941 ◽  
Author(s):  
Si Qian Zhang ◽  
Liang Mao ◽  
Li Jia Chen
Keyword(s):  
Dynamic Strain Aging ◽  
Strain Aging ◽  
Tensile Deformation ◽  
Rate Sensitivity ◽  
Dynamic Strain ◽  
Dynamic Strain Ageing ◽  
Strain Ageing ◽  
Serrated Flow ◽  
Chatelier Effect ◽  
Solute Atoms

Serrated flow has been observed in AZ81 alloy during tensile deformation. The observed static strain ageing effect and negative strain rate sensitivity suggest that the serrated flow is due to interaction between dislocations and solute atoms, know as dynamic strain ageing (DSA). The Portevin-Le Chatelier effect is observed at temperatures between 150oC~200oC and 125oC~200oC. In the microstructure of deformed samples dislocations and twins is observed. It is suggested that the occurrence of the dynamic strain aging is associated with interactions between solute atoms and dislocations.

Stress-State, Temperature, and Strain Rate Dependence of Vintage ASTM A7 Steel

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
S. A. Brauer ◽  
W. R. Whittington ◽  
H. Rhee ◽  
P. G. Allison ◽  
D. E. Dickel ◽  
...  
Keyword(s):  
Stress State ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Rate Dependence ◽  
Maximum Strength ◽  
Strain Rate Dependence ◽  
Dynamic Strain ◽  
Strength Increase ◽  
Negative Strain Rate Sensitivity

The structure–property relationships of a vintage ASTM A7 steel is quantified in terms of stress state, temperature, and strain rate dependence. The microstructural stereology revealed primary phases to be 15.8% ± 2.6% pearlitic and 84.2% ± 2.6 ferritic with grain sizes of 13.3 μm ± 3.1 μm and 36.5 μm ± 7.0 μm, respectively. Manganese particle volume fractions represented 0.38–1.53% of the bulk material. Mechanical testing revealed a stress state dependence that showed a maximum strength increase of 85% from torsion to tension and a strain rate dependence that showed a maximum strength increase of 38% from 10−1 to 103 s−1at 20% strain. In tension, a negative strain rate sensitivity (nSRS) was observed in the quasi-static rate regime yet was positive when traversing from the quasi-static rates to high strain rates. Also, the A7 steel exhibited a significant ductility reduction as the temperature increased from ambient to 573 K (300 °C), which is uncommon for metals. The literature argues that dynamic strain aging (DSA) can induce the negative strain rate sensitivity and ductility reduction upon a temperature increase. Finally, a tension/compression stress asymmetry arises in this A7 steel, which can play a significant role since bending is prevalent in this ubiquitous structural material. Torsional softening was also observed for this A7 steel.

Temperature Effects in Al 5083 with a Bimodal Grain Size

2013 ◽  
Vol 1513 ◽  
Author(s):  
Andrew C. Magee ◽  
Leila J. Ladani
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Cold Isostatic Pressing ◽  
Milling Process ◽  
Dynamic Strain ◽  
Plastic Properties ◽  
Al 5083 Alloy ◽  
Bimodal Grain Size

ABSTRACTAn Al 5083 alloy with a bimodal grain size has been previously synthesized using a low-temperature milling process and consolidation via cold isostatic pressing (CIP). This material has been shown to exhibit greatly improved strength when compared to conventional aluminum alloys. Additionally, this material has shown sensitivity to test conditions. In this work, we studied the effects of temperature on the strain rate sensitivity of this material by examining its elastic and plastic properties though uniaxial tension tests conducted under a variety of conditions at temperatures up to 473 K. Serrated stress-strain curves were observed, indicating dynamic strain aging. Strain rate sensitivity was found to depend non-monotonically on the test temperature.

Investigation of Dynamic Strain Ageing Effects of Low Alloy Steels 15Kh2MFA and 15Kh2NMFA

2005 ◽  
Vol 482 ◽  
pp. 367-370
Author(s):  
Miroslava Ernestová
Keyword(s):  
Strain Rate ◽  
Tensile Tests ◽  
Dynamic Strain ◽  
Low Alloy Steels ◽  
Strain Rates ◽  
Dynamic Strain Ageing ◽  
Strain Ageing ◽  
Lower Strain ◽  
Wide Range ◽  
Alloy Steels

The paper summarizes results of tensile tests in low alloy steel (LAS) specimens (steels 15Kh2MFA and 15Kh2NMFA). Slow Strain Rate Tensile tests (SSRT) were performed in air at temperatures from 22 to 325°C over a wide range of strain rates from 2.5×10-6 to 1.67×10-3 s-1. The possible effect of strain rate and temperature to mechanical properties of tested LAS is searched for. The dynamic strain ageing (DSA) was observed within certain temperature ranges at lower strain rates tested and its hardening effect in terms of the maximum strengthening stress decreased linearly with the increase of log strain rate. It has been found that the occurrence of susceptibility to environmentally assisted cracking (EAC) of tested steels in high temperature water (HTW) is corelated to the DSA behavior. The result suggest that DSA reduces ductility of reactor pressure vessel (RPV) steel and its role in enhancing the EAC of RPV steels should not be neglected, in view of the coincidence with susceptibility zones for DSA and EAC in terms of strain rate and temperature. A reasonable coincidence was observed between the susceptibility to DSA exhibited by SSRT in air and with the EAC behavior observed in laboratory experiments.

Amplitude Equation for a Dynamic Strain Aging Model: Beyond Linear Stability Analysis of Serrated Flow in Metallic Alloys

2000 ◽  
Vol 652 ◽  
Author(s):  
Sergey N. Rashkeev ◽  
Michael V. Glazov ◽  
Frédéric Barlat ◽  
Daniel J. Lege
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Qualitative Difference ◽  
Rate Sensitivity ◽  
Sudden Onset ◽  
Dynamic Strain ◽  
Strain Rates ◽  
Serrated Flow ◽  
Negative Strain Rate Sensitivity ◽  
First Case

ABSTRACTA method for construction of “processing windows” to avoid negative strain rate sensitivity and associated serrated flow in some aluminum alloys is described. The method is based on the amplitude Ginzburg-Landau (GL) equations and analysis of bifurcation diagrams. The mathematical technique developed in the present work was applied to a specific aluminum alloy, Al-0.4%Mg-0.2%Si considered earlier in the literature [1-3], and yielded good results in terms of predicting the negative strain rate sensitivity regions in the “strain rate “temperature” parameter space. Using the GL-analysis it was demonstrated that even though the instability area is located in the region of intermediate strain rates, a qualitative difference exists between the areas of (relatively) fast and (relatively) slow strain rates. In the first case the dynamic behavior of the system is supercritical, in the second case it is subcritical. The second case is highly undesirable because it causes a sudden onset of stable stress serrations that are difficult to suppress, while in the first case the development of instability is gradual and, consequently, more easily controllable.

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