Creep of olivine during hot-pressing

The densification curves for the hot-pressing of pure olivine powders were obtained as a function of grain size (5 μ–2000 μ), temperature (1000–1600°C), and compacting stress (166–298 bars). This range of variables was found to straddle two fields of hot-pressing behavior, one dominated by power-law creep, one by Coble creep. The time required to density a powder to 99% of the single crystal density could be represented by the shorter of the two times: t₁ = 2.2 · 10³σ^−3.4exp(85,000/RT)t₂ = 1.3 · 10⁴σ^−1.5(G)⁺³exp(85,000/RT) where the compacting stress or pressure, σ, is given in bars and the grain size, G, in centimeters. It was also possible to estimate the parameters appropriate to Coble creep in a solid polycrystalline aggregate from the hot-pressing data; and these were:

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The strain rates computed from this formula are close to those predicted by Stocker and Ashby (1973) and those found by Twiss (1976).