Research Progress of Lamellar Structure Coarsening Behavior in TiAl Based Alloy

Abstract:

Lamellar structure is the most important microstructure in TiAl alloy. We summarize the research progress of coarsening of lamellar structure in TiAl alloy so far, introduce the two types of the lamellar coarsening: continuous and discontinuous coarsening in TiAl lamellar structure, analyse thermodynamic driving force source, including chemical volume free energy, interface energy, elastic strain energy and grain boundary energy of lamellar coarsening, describe the dynamic characteristic of lamellar coarsening and discuss the influence factor of lamellar coarsening, incuding temperature, time, condition of microstructure, alloy elements and so on. On this basis, we astudy the lamellar coarsening of Ti-4822 alloy, describe and analyse its continuous and discontinuous coarsening of lamellar structure at elevated temperature and its change with temperature and time. We conclude that two coarsening types compete obviously at 1160 ℃. Discontinuous coarsening dominates at about eutectoid temperature while continuous coarsening dominates at higher temperature (above 1200 ℃) and discontinuous coarsening is suppressed.

Key words:TiAl alloy; lamellar structure; continuous coarsening; discontinuous coarsening