TY - JOUR
T1 - Relationship between fatigue life, changing of mechanical properties and dislocation structure during fatigue in pure titanium
AU - Akahori, Toshikazu
AU - Niinomi, Mitsuo
AU - Fukunaga, Kei Ichi
N1 - Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.
PY - 1999
Y1 - 1999
N2 - Mechanical properties, dislocation structure, fatigue strength and fatigue crack initiation characteristics were investigated at various fatigue steps in pure titanium having equiaxed α and Windmanstatten α structures. Relationship between fatigue life and the above mentioned factors was also studied. In pure titanium with both structures, long fatigue crack propagation life strongly affects fatigue strength and this life occupies total fatigue life as compared with small fatigue crack initiation and propagation life. The mechanical properties, that is, 0.2% proof stress and hardness tend to increase obviously according to the fatigue steps particularly at the early stage of the low cycle fatigue (LCF) region, whereas elongation shows the reverse trend. The hardness far from the specimen surface is smaller than that near the specimen surface at the early stage. Hardness of both areas becomes however nearly equal each other at the later stage. The reason why those phenomena occurred would be that increment of dislocation density near the specimen surface is larger than that far from the specimen surface at early stage and the dislocation density of both areas saturates at later stage, becoming similar. Dislocations in pure titanium with both structures form equiaxial dislocation cell structure. The dislocation structure at each fatigue step has a correlation with the fatigue life under constant maximum cyclic stress.
AB - Mechanical properties, dislocation structure, fatigue strength and fatigue crack initiation characteristics were investigated at various fatigue steps in pure titanium having equiaxed α and Windmanstatten α structures. Relationship between fatigue life and the above mentioned factors was also studied. In pure titanium with both structures, long fatigue crack propagation life strongly affects fatigue strength and this life occupies total fatigue life as compared with small fatigue crack initiation and propagation life. The mechanical properties, that is, 0.2% proof stress and hardness tend to increase obviously according to the fatigue steps particularly at the early stage of the low cycle fatigue (LCF) region, whereas elongation shows the reverse trend. The hardness far from the specimen surface is smaller than that near the specimen surface at the early stage. Hardness of both areas becomes however nearly equal each other at the later stage. The reason why those phenomena occurred would be that increment of dislocation density near the specimen surface is larger than that far from the specimen surface at early stage and the dislocation density of both areas saturates at later stage, becoming similar. Dislocations in pure titanium with both structures form equiaxial dislocation cell structure. The dislocation structure at each fatigue step has a correlation with the fatigue life under constant maximum cyclic stress.
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U2 - 10.2320/jinstmet1952.63.12_1527
DO - 10.2320/jinstmet1952.63.12_1527
M3 - Article
AN - SCOPUS:0033335351
VL - 63
SP - 1527
EP - 1534
JO - Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals
JF - Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals
SN - 0021-4876
IS - 12
ER -