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Different Annealing Temperature Affected TZM Alloy Plate Tensile Fracture

Observed at different annealing temperatures 80% compression ratio, 2.3mm TZM alloy’s tensile fracture morphology found the influence of annealing temperature on alloy’s tensile fracture (Fig.5-9). When the annealing temperature at 850 ℃, the tensile fracture of alloy is mainly transgranular fracture and there is significant cleavage steps on the fracture. In addition, there are a lot of voids in the fracture grain boundary. Besides, these holes will form the crack source stretching process, resulting alloy breakage.

After annealing at 1000 ℃, the fracture has obvious quasi-cleavage pattern river shape and cleavage steps. And this cleavage step formed in the process of crack propagation and dislocations cross-cut. Further, in the cleavage plane have some plastic deformation tearing ridge, so the alloy before breaking through a lot of plastic deformation rather than brittle fracture.

After annealing at 1150 ℃, the alloy fracture surface is similar with 1000 ℃ annealing fracture surface mainly quasi-cleavage fracture. The alloy having quasi-cleavage fracture the fracture plastic is better.

As we knew the recrystallization temperature of TZM alloy is about 1200 ℃. When the annealing temperature is 1300 ℃, the grains of alloy is more coarse and the fracture surface is relatively flat. And the fracture mode is mainly transgranular fracture and intergranular ductile fracture, indicated the plastic property has further improved. However, observed under 1300 ℃ annealing temperature alloy’s enlarged image found there has irregular particles and pits left by tensile fracture, as well as strengthening phase precipitated. This shows that when the annealing temperature is higher than the recrystallization temperature, it will weaken the dispersed phase and will reduce the mechanical properties of the alloy.

Therefore, during the stress relief annealing, the annealing temperature should be controlled below the recrystallization temperature. When the annealing temperature is higher than recrystallization temperature, although the plastic property is been improved, however the mechanical properties of the alloy is decrease.

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