| This study is concerned with the effects of microstructural parameters on the quasi-static tensile and dynamic torsional deformation behaviors in Ti-6Al-4V alloys with Widmansta¨tten structures. Dynamic torsional tests were conducted using a torsional Kolsky bar for five Widmansta¨tten structures, which effective grain sizes such as colony size and α lamellar spacing were varied by heat-treatments, and then the test data were analyzed in relation to microstructures, tensile properties, and fracture mode. Under dynamic torsional loading, maximum shear stress showed a large dependence on the colony size as the effective grain size, while shear strain at the maximum shear stress point was largely affected by both the α lamellar spacing and the colony size. Adiabatic shear bands were found in the deformed region of the fractured specimens, and their width was smallest in the specimen having the large α lamellar spacing and colony size. The possibility of the adiabatic shear band formation was quantitatively analyzed by the theoretical critical shear strain (γ_c) condition. It was found to be most likely in the coarse Widmanstatten structure, whereas least likely in the fine Widmanstatten structure. |
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