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Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Fatigue Crack Propagation Behavior in Commercial Purity Ti Severely Deformed by Accumulative Roll Bonding Process
Hiromoto KitaharaKosuke UchikadoJun-ichi MakinoNaomi IidaMasayuki TsushidaNobuhiro TsujiShinji AndoHideki Tonda
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2008 Volume 49 Issue 1 Pages 64-68

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Abstract

Fatigue properties of commercial purity titanium sheets severely deformed by the accumulative roll bonding (ARB) process were investigated. The ARB process was carried out up to 6 cycles (equivalent strain, εeq.=4.8). The sheets ARB processed by 2-, 4- and 6-cycle consist of fine equiaxed grains and elongated lamellar grains. In the sheet ARB processed by 6-cycle, the mean size of fine equiaxed grain was 89 nm, and the mean thickness of the lamellar grains were 67 nm. The tensile strength increased with increasing the number of the ARB cycle. Fatigue crack growth tests were performed to clarify the fatigue properties such as the crack growth rate and threshold stress intensity factor range for crack growth (ΔKth). The ΔKth of the ARB processed specimens were smaller than that of the starting sheet. The ΔKth decreased with increasing the number of the ARB cycle until 4-cycle. However, the ΔKth of 6-cycle specimen was larger than that of the 4-cycle specimen. Fracture surface of the 6-cycle specimen was different from that of the 2- and 4-cycle specimens. Fatigue crack propagation behavior changes between 4- and 6-cycle specimens. On the other hand, the crack growth rate decreases with increasing the number of the ARB cycle.

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© 2008 The Japan Institute of Metals and Materials
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