TY - JOUR
T1 - High temperature impact properties and dislocation substructure of Ti–6Al–7Nb biomedical alloy
AU - Lee, Woei Shyan
AU - Chen, Chia Wei
N1 - Funding Information:
The authors gratefully acknowledge the financial support provided to this study by the National Science Council (NSC) of Taiwan under Contract no. NSC 100-2221-E-006-062 .
Publisher Copyright:
© 2013 Elsevier B.V.
PY - 2013/8/1
Y1 - 2013/8/1
N2 - The high temperature deformation and dislocation substructure of Ti–6Al–7Nb biomedical alloy are investigated under high strain rate loading conditions using a split-Hopkinson pressure bar. Impact tests are performed at strain rates ranging from 1×103 s−1 to 3×103 s−1 and temperatures of 300 °C and 700 °C, respectively. The experimental results show that the flow stress, work hardening coefficient and strain rate sensitivity all increase with increasing strain rate, but decrease with increasing temperature. Moreover, the fracture observations reveal that the Ti–6Al–7Nb specimens fail predominantly as the result of intensive localised shearing. The fracture surfaces of the deformed specimens contain both cleavage structures and dimple-like structures. Transmission electron microscopy observations reveal that the dislocation density increases with increasing strain rate, but decreases with increasing temperature. A pronounced thermal softening effect is observed in the specimens deformed at 700 °C due to a rapid annihilation of the dislocations. However, a work hardening effect occurs at higher strain rates and lower temperatures due to an enhanced degree of dislocation multiplication and tangling. Finally, a linear relationship is observed between the square root of the dislocation density and the flow stress.
AB - The high temperature deformation and dislocation substructure of Ti–6Al–7Nb biomedical alloy are investigated under high strain rate loading conditions using a split-Hopkinson pressure bar. Impact tests are performed at strain rates ranging from 1×103 s−1 to 3×103 s−1 and temperatures of 300 °C and 700 °C, respectively. The experimental results show that the flow stress, work hardening coefficient and strain rate sensitivity all increase with increasing strain rate, but decrease with increasing temperature. Moreover, the fracture observations reveal that the Ti–6Al–7Nb specimens fail predominantly as the result of intensive localised shearing. The fracture surfaces of the deformed specimens contain both cleavage structures and dimple-like structures. Transmission electron microscopy observations reveal that the dislocation density increases with increasing strain rate, but decreases with increasing temperature. A pronounced thermal softening effect is observed in the specimens deformed at 700 °C due to a rapid annihilation of the dislocations. However, a work hardening effect occurs at higher strain rates and lower temperatures due to an enhanced degree of dislocation multiplication and tangling. Finally, a linear relationship is observed between the square root of the dislocation density and the flow stress.
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U2 - 10.1016/j.msea.2013.03.088
DO - 10.1016/j.msea.2013.03.088
M3 - Article
AN - SCOPUS:84877068366
SN - 0921-5093
VL - 576
SP - 91
EP - 100
JO - Materials Science and Engineering A
JF - Materials Science and Engineering A
ER -