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Influence of heat treated microstructures on the dynamic deformation characteristics of Ti-6Al-4V alloy

Title
Influence of heat treated microstructures on the dynamic deformation characteristics of Ti-6Al-4V alloy
Author
김태원
Keywords
Ti-6Al-4V alloy; Microstructure; Dynamic deformation; Shear crack; Compressive SHPB test
Issue Date
2015-12
Publisher
KOREAN SOC MECHANICAL ENGINEERS
Citation
JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY, v. 29, NO 12, Page. 5223-5232
Abstract
We investigated the influence of heat treated microstructures, namely, equiaxed, bimodal and lamella types of Ti-6Al-4V alloy on the dynamic deformation characteristics. Four different heat treatment conditions were employed for the development of the microstructures. Static tensile and compressive deformation tests were preliminarily performed with hydraulic test equipment. Dynamic deformation tests at a high level of strain rate, 2700 s(-1) similar to 6400 s(-1), together with high velocity impact tests were, respectively, conducted on the specimens through a compressive Split Hopkinson pressure bar (SHPB) and a high pressure gas gun system. The dependence of flow stress on the strain rate associated with the corresponding microstructure was examined. The microstructural factors on the dynamic fracture characteristics were analyzed by scanning electron microscopy. The static compressive tests showed that the flow stress was greatest in the lamella microstructure and decreased in the order of lamella, bimodal and equiaxed microstructures, whereas the ductility was largest in the bimodal microstructure and smallest in the lamellar microstructure. In dynamic compressive tests, a similar dependency of the flow stress on microstructures was observed: highest in the lamellar microstructure and lowest in the equiaxed microstructure. The ductility, such as strain at maximum stress or at failure, was highest in the equiaxed microstructure and lowest in the lamellar structure. In addition, the ductility for individual microstructure decreased as the strain rate increased. Every microstructure exhibited ductile fracture surfaces, and it seems that a large shear crack on the lateral surface in the specimen was the main factor inducing the final failure. The result of high velocity impact test exhibited that the resistance to fracture of equiaxed microstructure with superior dynamic toughness was much higher than that of lamella microstructure with inferior dynamic toughness. The results obtained help provide a fundamental idea and guide to improve the dynamic mechanical properties of Ti-6Al-4V alloy through the microstructure control.
URI
https://link.springer.com/article/10.1007%2Fs12206-015-1122-xhttp://hdl.handle.net/20.500.11754/30151
ISSN
1738-494X; 1976-3824
DOI
10.1007/s12206-015-1122-x
Appears in Collections:
COLLEGE OF ENGINEERING[S](공과대학) > MECHANICAL ENGINEERING(기계공학부) > Articles
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