Effect of Heat Treatment and Thermal Exposure on Microstructure of the Alloy C<sup>+</sup> Bars

Abstract

The microstructures of the Alloy C+ with three different heat treatment processes have been investigated after exposure at 550 °C for 100 hours in this study. The alloy shows typical equiaxed β grains with second phase precipitation and twin formation inside the β grains in the as-rolled condition. Solution treatment at lower temperature led to a smaller β grain size while higher temperature solution treatment produced coarse grains with increasing precipitated phases inside the β grains. Ageing treatment after solution and thermal exposure for a long period of time resulted in an increasing α phase precipitation at the grain boundaries due to their tendency for preferential nucleation of second phases. In a certain condition, continuous coarsening of the α phase is concentrated on the grain boundaries therefore violate the properties of the alloy.