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Molybdenum and TZM Alloy Heat Treatment after Plastic Deformation

Molybdenum and TZM alloy after processing to a certain extent, that is hardening to a certain extent, should to be treated by annealing treatment making material soften, so that it can continue to process machining deformation, to reduce reparation, breakage and other phenomena during using process. After plastic deformation molybdenum and TZM alloy should go through heat treatment at different temperatures and its structure and properties has different changes.

Heating hardening molybdenum and TZM alloy at a temperature below recrystallization temperature to basic eliminate internal stress and to reduce processing deformation resistance, namely stress annealing. After stress annealing, molybdenum and TZM alloy crystal defects can be certain to eliminate and distortion degree of the grains can be reduced. Besides, the resistance decreased and the internal stress reduced significantly. On the other hand, the grains shows substructure change, which to some extent reduced the distortion degree of the crystal grains. There is recrystallization brittle in molybdenum and its alloys, so during stretching in order to reduce the work hardening should relief portion stress, for plasticity improving and further processing, in which the heat treatment after the plastic deformation can only be stress annealing.

Recrystallization temperature of molybdenum and TZM alloy playing an important role on formulate annealing process and the heating temperature, so working out the recrystallization temperature has great significance. When the deformed material is heated to a certain extent, in the original deformation tissue will re-form a new grain without distortion, and its performance has also undergone dramatic changes, resulting in complete recovery, this process is called recrystallization. For pure molybdenum, the greater the deformation degree is, the lower the recrystallization temperature. Added trace metals into molybdenum can produce TZM alloy, which has higher recrystallization temperature than pure molybdenum. In general, the longer the heating time, the slower the heating rate, the recrystallization temperature is lower. The finer original grain before annealing, the recrystallization temperature is lower.

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