Annealing behaviour and transient high-heat loading performance of different grade fine-grained tungsten

Abstract

The annealing-induced grain growth behaviour and the transient high-heat loading performance of several W grades, including laboratory fine-grained W, oxide dispersion strengthened (ODS) W and commercial W, were measured and compared. The results show that the starting temperature causing grain growth for pure W (both laboratory fine-grained W and commercial W) is not very high, about 1300° C. The finer the initial grain size of pure W, the stronger the grain growth after annealing at high temperature. But for the pure W with a very fine initial grain size, the grain size after high-temperature annealing is still not very coarse; it is less than that of commercial W. For the ODS W, only slight grain growth occurred even after annealing at a temperature of 1900° C. Transient high-heat loading tests show that the surfaces of fine-grained W and ODS W tend to surface melting. For fine-grained pure tungsten, this is attributed to the low material density, which leads to a relatively bad heat transfer to the bulk and, for the ODS W, to a lower melting point of the oxide phase.