Molybdenum News Center

High Temperature Deformation Behavior of TZM Alloy

The TZM alloy is a commonly used constructional material for high-temperature applications. It is well known that TZM alloys develop a distinct subgrain structure and texture during hot deformation. These microstructural aspects have a significant effect on strength at high temperatures. It was observed that with proceeding primary recrystallization the subgrains is disappearance and the yield strength drops almost to the same level of pure molybdenum. The aim of the present work was to investigate and describe the strain hardening of hot deformed TZM on a microstructural basis. For this purpose sintered and prerolled TZM rods were recrystallized and each of them deformed to a specific degree of deformation afterwards. Especially the evolution of disorientation distributions was analyzed by electron backscattering diffraction (EBSD) and used to describe the work hardening effect. The yield strength was determined by tensile tests between room temperature and 1473 K. By analyzing disorientation profiles the deformation and evolution of geometrically necessary and incidental dislocation boundaries could be observed. A model developed by Pantleon was used to describe the work hardening of TZM.

A strong work hardening effect in TZM was reported earlierr. The tendency of pure molybdenum to form dislocation networks during hot deformation is well known. Results for Mo single and polycrystals were reported. The aim of this work is to provide a better microstructure-based understanding of the work hardening behaviour of TZM.

Work hardening is commonly expressed by plotting the work hardening rate versus the flow stress.Normally so called stage-III behaviour is observable. Depending on the strain path a stages IV and V may be present too. For stage III there is the common understanding that hardening is caused by generation and storage of dislocations resulting in the formation of dislocation walls.

• < Prev
• Next >