The importance of mechanical twinning in the stress-strain behavior of swaged high purity fine-grained titanium below 424°K
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Zone-refined iodide titanium specimens, swaged and annealed at different temperatures to give a range of grain sizes from 2.4 to 22 μ, were deformed to fracture between 77° and 424°K. A metallographic study of the fractured specimens revealed that mechanical twinning is an important factor in the plastic deformation of this grade of titanium at subambient temperatures. In all cases, the volume fraction of twins increased steadily with strain as well as with decreasing deformation temperature. At 77°K and at a grain size of 22 μ, the twin volume fraction was greater than 0.5 at a strain of 0.5. Furthermore, each of the 77°K stress-strain curves showed a linear work-hardening character with an associated high ductility similar to that originally reported by Wasilewski for commercial purity titanium. The nearly linear stress-strain curve in this latter case has been rationalized earlier in terms of deformation twinning. The present results are in good agreement with this point of view.
KeywordsDeformation Twinning Mechanical Twinning Commercial Purity Titanium Twin Volume Fraction Subambient Temperature
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