Abstract
The utralow-temperature superplastic forging for sialon-based nanocomposites is reported for the first time. Sialon-based nanocomposites, with an average grain size smaller than 50 nm and 98.5% relative density, were prepared with nano-sized row powders by the spark plasma sintering (SPS) technique at a record ultralow sintering temperature of 1150 °C. An excellent gear is forged at the ultralow deformation temperature of 1200 °C with nanosized grains without any cracking. The maximum strain rate achieved is over 10−1 s−1, and a compression strain is more than 0.9. The practical application for superplastic forming of nitrogen ceramics is much more difficult than that for oxide ceramics because of the high deformation temperature and low strain rates. The present findings present a bright prospect for the near-net-shape superplastic forming of nitrogen ceramics.
Highlights
As high-temperature structural materials, silicon nitride-based ceramics are the excellent mechanical properties, high melting temperature, low density, high elastic modulus and strength, and good resistance to creep, wear and oxidation
By using four kinds of nano-sized powders and applying spark plasma sintering (SPS) technology, the authors have developed superplastic sialon-based nanocomposite with 50 nm grain size and investigated its formidable deformation capability of superplastic forging at low temperature of 1200 °C and high strain rate over 10−2 s−1
The punch displacement data obtained plotted vs. sintering temperature for sailon-based ceramic in a ZRY-120 furnace and in an SPS apparatus are shown in Fig. 1, respectively
Summary
As high-temperature structural materials, silicon nitride-based ceramics are the excellent mechanical properties, high melting temperature, low density, high elastic modulus and strength, and good resistance to creep, wear and oxidation. The low-temperature and high-strain-rate superplastic forming of oxide ceramics nanocomposites were reported by Zhan[20] et al and the application research has spread widely[21].
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