Evolution of microstructure and texture in a warm-rolled yttria dispersion-strengthened tungsten plate during annealing in the temperature range between 1200 °C and 1350 °C

Abstract

The thermal stability of an yttria dispersion-strengthened tungsten plate warm-rolled to 50% thickness reduction is investigated. Isothermal annealing experiments were conducted at four temperatures and the microstructure and texture evolution were analyzed with Transmission Electron Microscopy (TEM) and Electron Backscatter Diffraction (EBSD) to understand the restoration mechanisms in the W-2 vol% Y2O3 alloy. At 1200 °C, dominantly recovery occurred in the warm-rolled plate up to the longest annealing time of 84 h, whereas at temperatures of 1250 °C and above recrystallization was the dominant restoration mechanism. Microstructure and texture evolution during recrystallization were quantified in terms of grain size, aspect ratio and volume fractions of fiber texture components. The analysis reveals that the Y2O3 particles play a key role in the recrystallization mechanism of the plate affecting both, nucleation and growth behavior. Their dominating effect originates from pinning of high angle boundaries causing no-convex grain shapes as well as slower recrystallization kinetics than pure tungsten, thereby improving the thermal stability of the oxide dispersion-strengthened material.