Static and Dynamic Strain Aging in Two-Phase γ-Titanium Aluminides

1996 ◽  
Vol 460 ◽  
Author(s):  
U. Christoph ◽  
F. Appel ◽  
R. Wagner
Keyword(s):  
Mechanical Properties ◽  
Activation Energy ◽  
Strain Aging ◽  
Titanium Aluminides ◽  
Rate Sensitivity ◽  
Dynamic Interaction ◽  
Dynamic Strain ◽  
Two Phase ◽  
Fast Kinetics ◽  
Negative Strain Rate Sensitivity

ABSTRACTDeformation of two-phase titanium aluminides exhibits discontinuous yielding and a negative strain rate sensitivity over the temperature range 450–750 K. These phenomena are usually associated with the Portevin-LeChatelier effect which is due to the dynamic interaction of diffusing defects with the dislocations. The resulting glide resistance was investigated by static strain aging. The experiments involve the prestraining of samples followed by aging under a relaxing load for certain periods of time. Reloading of the samples resulted in distinct yield points. The investigations were performed on two-phase γ-titanium aluminides having different compositions and microstructures which are currently being considered for technical applications. Accordingly, dislocation locking occurs with fast kinetics which is characterized by a low activation energy. The experimental results will be discussed with respect to the nature of the diffusional mechanism and possible implication on the mechanical properties of the materials.

Static and Dynamic Strain Ageing in Two-Phase Gamma Titanium Aluminides

2000 ◽  
Vol 646 ◽  
Author(s):  
U. Christoph ◽  
F. Appel
Keyword(s):  
Titanium Aluminide ◽  
Titanium Aluminides ◽  
Deformation Behaviour ◽  
Dynamic Strain ◽  
Dynamic Strain Ageing ◽  
Two Phase ◽  
Fast Kinetics ◽  
Strain Ageing ◽  
Wide Range ◽  
Dislocation Pinning

ABSTRACTThe deformation behaviour of two-phase titanium aluminides was investigated in the intermediate temperature interval 450–750 K where the Portevin-LeChatelier effect occurs. The effect has been studied by static strain ageing experiments. A wide range of alloy compositions was investigated to identify the relevant defect species. Accordingly, dislocation pinning occurs with fast kinetics and is characterized by a relatively small activation energy of 0.7 eV, which is not consistent with a conventional diffusion process. Furthermore, the strain ageing phenomena are most pronounced in Ti-rich alloys. This gives rise to the speculation that antisite defects are involved in the pinning process. The implications of the ageing processes on the deformation behaviour of two-phase titanium aluminide alloys will be discussed.

Dynamic Strain Aging in the Fe-Mn-Cu-C TWIP Steels

2013 ◽  
Vol 668 ◽  
pp. 861-864 ◽  
Author(s):  
Hai Jun Liu ◽  
Ding Yi Zhu ◽  
Xian Peng ◽  
Zhen Ming Hu ◽  
Ming Jie Wang
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Dynamic Strain Aging ◽  
Strain Aging ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Dynamic Strain ◽  
Work Hardening Rate ◽  
Twip Steels ◽  
High Work

Strain rate jump tests were performed on the Fe-Mn-Cu-C TWIP Steels to determine the strain rate sensitivity, and serrated plastic flow was observed in the stress-strain curves during tensile tests at different constant strain rates ranging from 2.5×10-4S-1 to 2.5×10-2S-1. The Fe-Mn-Cu-C TWIP Steels exhibit high work hardening rate and outstanding mechanical properties, The excellent mechanical properties are attributed to dynamic strain aging(DSA) effect, which result from the interaction between Mn(Cu)-C atom atmosphere, C-vacancy, C-C pairs and moving dislocations.

Incorporation of Dynamic Strain Aging Into a Viscoplastic Self-Consistent Model for Predicting the Negative Strain Rate Sensitivity of Hadfield Steel

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
B. Bal ◽  
B. Gumus ◽  
D. Canadinc
Keyword(s):  
Strain Rate ◽  
Strain Hardening ◽  
Strain Rate Sensitivity ◽  
Strain Aging ◽  
Rate Sensitivity ◽  
Atomic Level ◽  
Hadfield Steel ◽  
Dynamic Strain ◽  
Deformation Response ◽  
Negative Strain Rate Sensitivity

A new multiscale modeling approach is proposed to predict the contributions of dynamic strain aging (DSA) and the resulting negative strain rate sensitivity (NSRS) on the unusual strain-hardening response of Hadfield steel (HS). Mechanical response of HS was obtained from monotonic and strain rate jump experiments under uniaxial tensile loading within the 10−4 to 10−1 s−1 strain rate range. Specifically, a unique strain-hardening model was proposed that incorporates the atomic-level local instabilities imposed upon by the pinning of dislocations by diffusing carbon atoms to the classical Voce hardening. The novelty of the current approach is the computation of the shear stress contribution imposed on arrested dislocations leading to DSA at the atomic level, which is then implemented to the overall strain-hardening rule at the microscopic level. The new model not only successfully predicts the role of DSA and the resulting NSRS on the macroscopic deformation response of HS but also opens the venue for accurately predicting the deformation response of rate-sensitive metallic materials under any given loading condition.

scholarly journals Effect of Aging Process on the Strain Rate Sensitivity in V-Containing TWIP Steel

Metals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 126
Author(s):  
Shaoheng Sun ◽  
Zhiyong Xue
Keyword(s):  
Tensile Strength ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Strain Aging ◽  
Aging Process ◽  
Vanadium Carbide ◽  
Twip Steel ◽  
Rate Sensitivity ◽  
Dynamic Strain ◽  
Negative Strain Rate Sensitivity

The dynamic tensile behavior of the twinning-induced plasticity (TWIP) steel with the vanadium carbide is investigated at different strain rates of 10−4, 10−3, 10−2 and 0.05 s−1. Microstructure characterization, carried out using back scatter electron diffraction (EBSD) and transmission electron microscopy (TEM), shows a homogeneous face center cubic structured matrix with uniformly dispersed vanadium carbide. The vanadium carbide is controlled by the aging temperature and time. The best comprehensive mechanical properties are achieved when the tested steel is aged at 550 °C for 5 h. With the increase of strain rate, the tensile strength and work hardening rate decrease, and the tested material shows negative strain rate sensitivity. This would be due to an increase in stacking fault energy caused by temperature rise by adiabatic heating, which must suppress the formation of twinning. On the other hand, the strain rate sensitivity is affected by dynamic strain aging (DSA). With the increase of strain rate, the DSA weakens, which causes negative strain rate sensitivity. The tensile strength and strain rate sensitivity value both increase first and then decrease with the increase of vanadium carbide size. This is because the tensile strength is mainly affected by the vanadium carbide. In addition to the vanadium carbide, the strain rate sensitivity is also affected by the amount of solute atom (V and C) during the dynamic strain aging process.

Hot work processing, microstrructure and mechanical properties of two-phase γ titanium aluminides

1994 ◽  
Vol 185 (1-2) ◽  
pp. 17-24 ◽  
Author(s):  
X.D. Zhang ◽  
R.V. Ramanujan ◽  
T.A. Dean ◽  
M.H. Loretto
Keyword(s):  
Mechanical Properties ◽  
Titanium Aluminides ◽  
Two Phase

Evaluation of activation energy for dynamic strain aging process in 316L(N)/316(N) SS weld joints

2008 ◽  
Vol 61 (4) ◽  
pp. 301-306 ◽  
Author(s):  
M. Shanmugavel ◽  
M. Nandagopal ◽  
R. Sandhya ◽  
K. Bhanu Sankara Rao ◽  
R. Gnanamoorthy
Keyword(s):  
Activation Energy ◽  
Dynamic Strain Aging ◽  
Strain Aging ◽  
Aging Process ◽  
Dynamic Strain ◽  
Weld Joints

scholarly journals Behavior of Dynamic Strain Aging in Zr-1.5Nb-0.4Sn-0.2Fe-0.1Cr Alloy Strip

2021 ◽  
Vol 59 (1) ◽  
pp. 8-13
Author(s):  
Il-Hyun Kim ◽  
Myung-Ho Lee ◽  
Yang-Il Jung ◽  
Hyun-Gil Kim ◽  
Jae-Il Jang
Keyword(s):  
Tensile Test ◽  
Strain Rate ◽  
Dynamic Strain Aging ◽  
Strain Aging ◽  
Rolling Direction ◽  
Rate Sensitivity ◽  
Dynamic Strain ◽  
Alloy Strip ◽  
Lower Strain ◽  
Temperature Ranges

The behavior of dynamic strain aging (DSA) in a Zr-1.5Nb-0.4Sn-0.2Fe-0.1Cr alloy strip was investigated at temperature ranges of 25–600 °C via a tensile test. The tensile test was performed at two different strain rates 8.33 × 10<sup>-5</sup> and 1.67 × 10<sup>-2</sup> s<sup>-1</sup>. The shear stress of the alloy strip revealed a linear dependency on the test temperature when the specimens were tested under a higher strain rate (1.67 × 10<sup>-2</sup> s<sup>-1</sup>). However, the linear relationship was broken due to DSA when the samples were deformed under a lower strain rate (8.33 × 10<sup>-5</sup> s<sup>-1</sup>). The discrepancy was most significant at 400 °C. The trend in DSA behavior was similar irrespective of the orientation of the samples, i.e., rolling direction (RD) or transverse direction (TD). However, the effect of DSA was larger in the TD samples than the RD samples. The phenomena were interpreted to the variation in work hardening exponents and strain rate sensitivity. The value of the exponent decreased from 0.14 to 0.08 along a RD and from 0.1 to 0.07 along a TD, respectively. However, the smallest value was observed at 400–500 °C irrespective of the specimen orientation, which is consistent with the DSA behavior. It is suggested that the DSA was caused by an interaction of moving dislocations with solute atoms typically oxygen.

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