The effect of dynamic strain ageing on the anomalous strain-rate-dependent tensile strain of Zircaloy-4

1990 ◽  
Vol 9 (10) ◽  
pp. 413-415 ◽  
Author(s):  
Jong Sik Ahn ◽  
Soo Woo Nam
Keyword(s):  
Strain Rate ◽  
Tensile Strain ◽  
Dynamic Strain ◽  
Dynamic Strain Ageing ◽  
Strain Ageing ◽  
Rate Dependent

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.

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).

Temperature and Strain Rate Effects on the Dynamic Strain Ageing of Aluminium Alloy AA7030

2006 ◽  
Vol 519-521 ◽  
pp. 883-888 ◽  
Author(s):  
Magnus Hörnqvist ◽  
Birger Karlsson
Keyword(s):  
Strain Rate ◽  
Temperature Dependence ◽  
Aluminium Alloy ◽  
Surface Deformation ◽  
Dynamic Strain ◽  
Dynamic Strain Ageing ◽  
Aged Material ◽  
Strain Ageing ◽  
Serrated Yielding ◽  
Peak Aged

The effects of temperature and strain rate on the mechanical properties of aluminium alloy AA7030 (Al-5.4Zn-1.2Mg) in naturally aged and peak aged condition are investigated, with emphasis on the relation to dynamic strain ageing. It is found that the naturally aged material shows more severe signs of dynamic strain ageing, including inverse strain rate and temperature dependence of flow stress, inverse temperature dependence of the ductility and serrated yielding. The peak aged material also shows signs of dynamic strain ageing, but to a lesser extent, most pronounced through serrated yielding. The observed effects can be qualitatively explained in terms of a thermal activation based model for dislocation glide. Furthermore, inhomogeneous deformation is observed on several size scales ranging from localized glide bands to surface deformation effects (orange peel surface) and macroscopic flow localization in shear bands.

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