Microstructure and mechanical properties of commercial purity titanium severely deformed by ARB process |
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Authors: | Daisuke Terada Seiya Inoue Nobuhiro Tsuji |
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Affiliation: | (1) Department of Adaptive Machine Systems, Graduate School of Engineering, Osaka University, Osaka, Japan |
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Abstract: | Commercial purity titanium was deformed by accumulative roll-bonding (ARB) process up to 8 cycles (equivalent strain of 6.4)
at ambient temperature. This is the first study on ultra-high straining of h.c.p. metals by the ARB process. The microstructure
of the ARB-processed specimens showed two kinds of characteristic ultrafine microstructures. One was the lamellar boundary
structure elongated along RD, which has been also reported in the ARB-processed cubic metals. The lamellar boundary spacing
decreased with increasing ARB strain and reached about 80 nm after 5 ARB cycles. The other microstructure was the equiaxed
grains having mean grain size of 80–100 nm. Such a fine and equiaxed grain structure has not yet been reported in the as-ARB-processed
materials before. The fraction of the equiaxed grains increased as the ARB process proceeded, and 90% of the specimen was
filled with the equiaxed grains after 8 ARB cycles. As the number of the ARB process increased, the tensile strength increased
and the total elongation decreased gradually. After 6 ARB cycles, the specimen exhibited almost the same mechanical properties
as that of commercial Ti-6Al-4V alloy. |
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