Different Annealing Temperatures Influence TZM Alloy’s Fracture Morphology

Different annealing temperatures, tensile fracture morphology of TZM alloy is not the same. When annealing temperature is 850 ℃, the tensile fracture of TZM alloy is mainly transgranular fracture. There is a significant cleavage step on the fracture. And there are a lot of holes in fracture grain boundary. Besides, these holes are formed crack sources in the stretching process which causes alloy break by interconnected. Annealed at 1000 ℃, the fracture has obvious river-like pattern and cleavage step. When the cracks expansion will connect with dislocation and therefore will generate cleavage step. Meanwhile, the alloy before breaking through a lot of strain, so there has been a lot of tearing ridge on cleavage surface. When the annealing temperature is 1150 ℃, the fracture characteristics is similar to 1000 ℃ fracture characteristics, but the degree of cleavage fracture has improved, so the breaking plastic of alloy also increased.

Recrystallization temperature of TZM alloy is about 1200 ℃, when the annealing temperature exceeds the recrystallization temperature, the alloy has coarse grains, the fracture surface is relatively flat. The fracture is mainly transgranular fracture and ductile fracture which is mean plastic of alloy has been further increase. But there have been many irregularities particles and pits in the alloy and there are enhanced phase precipitate in local area. This shows the high annealing temperature weakened dispersion strengthen and have a certain influence on the mechanical properties of the alloys. Therefore, the annealing temperature should be controlled below the recrystallization temperature of TZM alloy.