2001 Volume 42 Issue 11 Pages 2398-2405
The phase transformations in a Ti–10 mass%Zr alloy during continuous cooling and isothermal holding have been investigated mainly by means of hot stage optical microscopy. During cooling from β phase at 100°C/s, α′ plates formed martensitically at temperatures around 180°C together with sharp and coarse surface reliefs. The Widmanstätten α laths mostly nucleated directly on a β phase grain boundary and grew into one of the grains during isothermal holding at temperatures between 650 and 850°C. At β grain boundaries, α allotriomorphs often nucleated and Widmanstätten α laths grew from them during isothermal holding at 800°C. Widmanstätten α plates exhibited sharp surface reliefs. The precipitation of α phase exhibited the C-curve with the nose at around 775°C. The Ms temperature so far reported to be ∼ 805°C is not the martensite start temperature but the nose temperature for Widmanstätten α laths.