High-temperature stress relaxation of synthetic,polycrystalline galena |
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| Authors: | Barry Kean Atkinson |
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| Institution: | 1. Department of Geology, Imperial College of Science and Technology, SW7 2BP, London, Great Britain
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| Abstract: | Stress relaxation experiments were performed on hot-pressed cylinders of synthetic, polycrystalline galena at temperatures of 500°, 600°, 700° and 800°C at atmospheric pressure after various levels of axial strain, in the range from 2% to 25%, had been imposed at a constant strain rate (?) of 3×10?4 s?1. For this study a new apparatus was built which can measure small changes in applied stress (σ), better than ±0.5 × 105 Pa, and which incorporates a facility whereby the composition of the test specimen can be fixed through equilibration with a gas atmosphere of controlled composition. Deformation mechanism maps constructed largely on theoretical grounds predict that, under the conditions studied here, high-temperature dislocation creep, for which ?∝σ5, gives way on lowering the applied stress to diffusion creep, for which ?∝σ. The experimental results agree in large measure with these theoretical predictions. However, it is not possible in this preliminary study to conclusively identify the dominant deformation mechanisms. |
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