Enhancement of high-temperature deformation in fine-grained silicon carbide with Al doping

Diffusion-driven superplasticity in ceramics: Modeling and comparison with available data

“…Tokiyama et al 23 have recently studied the hightemperature deformation of Al-doped SiC polycrystals. The authors report a transition in the stress-exponent value, which increases from n Ϸ 1.4 to n Ϸ 2.6 when the stress decreases.…”

“…23 The model by Artz, Ashby, and Verrall states that the flow stress is proportional to the number of grain-boundary dislocations. When the number N of dislocation per grain-boundary interface is limited, a multiplicative factor N 2 / ͑N 2 +1/ 2͒ is introduced in the conventional equation for steady-state creep.…”

“…III A, we take the transition stress at n = 1.5, which corresponds to ␤ = 0.3. Tokiyama et al 23 indicate that accommodation is mainly driven by grain-boundary diffusion, thus D eff Ϸ D gb . With ␦ Ϸ a and ␣ Ϸ 0.5, Eq.…”

Spark plasma sintering and pressureless sintering of SiC using aluminum borocarbide additives

“…The former reports mostly used hot pressing for densification. 1,2,5 In contrast, SPS was applied in the present investigation. During SPS, oxide layers formed on non-oxide ceramic powders were reported to be removed due to the ultrarapid heating of the powder surface and by the formation of discharge and plasma.…”

“…1,2 In spite of the advantages, large flakes of metal aluminum may form during milling process, which may cause the formation of flaws and the inhomogeneous distribution of additives in sintered SiC. The flakes can be crushed by increasing milling energy, but the resultant powder mixture may require careful handling in an inert atmosphere due to the rapid oxidation reaction of the crushed fine aluminum powder in air.…”