The plastic flow behaviour of a β-titanium alloy (Ti-15% Mo) was investigated over a wide range of temperatures and strain rates covering those conditions where the ω-phase forms dynamically. Portevin-Le Chatelier (PLC) effect was observed in this alloy at temperatures between 575 and 775 K at a strain rate of 1.31 × 10−4 s−1. The serrated flow behaviour of this alloy could be suppressed by rendering the matrix β-phase more stable against the β to ω transformation. PLC bands formed in this alloy, studied at different levels of magnification using light, scanning electron and transmission electron microscopy, showed a high density of deformation bands within the macroscopic PLC band. The following mechanism of serrated flow is proposed: the load drop is ascribed to the sudden flow associated with the formation of deformation bands within which ω-particles were destroyed while the subsequent load rise results from pinning of dislocations by ω-particles forming dynamically.
This paper as originally published in Acta Materialia 44 (1996) Pages 3667 - 3677
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