Fracture Toughness of Widmanstatten Colonies of an Alpha-Beta Titanium Alloy.
MICHIGAN TECHNOLOGICAL UNIV HOUGHTON DEPT OF METALLURGICAL ENGINEERING
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The fracture toughness behavior of individual alpha plus Beta Widmanstatten colonies of the Ti-8Al-1Mo-1V alloy in the form of sheet has been investigated. Crack extension occurs predominantly across the Alpha-Beta lamellae under conditions of plane stress and on planes which are inclined both to the thickness and the width of specimens. Polycrystalline material has also been examined and is observed to exhibit fracture along a plane inclined through the thickness but not inclined across the width. Crack-tip plasticity in both types of material is dominated by through-thickness deformation involving slip and often twinning. In the single colony specimens, the crack-tip plasticity has been characterized experimentally by identifying the active sliptwinnning planes and by calculating the distribution of shear stresses on the possible deformation systems, using a maximum, macroscopic shear stress criteria. As suggested by the fracture behavior of the polycrystalline specimens, the macroscopic fracture plane across individual colonies is near that slip or twinning plane which experiences the largest shear stress when the macroscopic shear stress is a maximum.
- Properties of Metals and Alloys