In all cases, necking and grain growth are obvious as grains are cohesive,with sizes higher than the initial particles (40–100 nm). The evolution of grain size dwell versus time presented in Fig. 6 insets and Fig. 7 depends on the process. In the case of HS, the grain size increases from 166 ± 55 to 229 ± 70 nm, reaching a plateau from ∼ 40 min (HS40).