Observation of Grain Boundary Sliding of Aluminum Bicrystals by Thermostable Moiré Method

Obata Mitsuo, Shimada Heihachi

doi:10.2320/jinstmet1952.40.2_112

The grain boundary sliding and the deformation in the vicinity of the grain boundary were studied at a high temperature by the moiré method instead of using a markerline and a dial gage extensometer. Pure aluminum (99.99 wt%) bicrystals with the grain boundaries oriented at an angle (θ) of 30°, 45°, or 60° to the tensile axis were deformed in air under a constant load. The initial tensile stress was 75 g/mm² and the testing temperature were 350, 400 and 450°C. The optical system of the image moiré method was improved by the authors. According to the improved system, two families of moiré fringe patterns were separated by a beam spliter and imaged on independent screens. The density of reference and thermostable specimen gratings was 1000 lines/inch. The deformation in the vicinity of the grain boundary was measured by observing the deformation of specimen grating. The main results obtained are summarized as follows: (1) The distribution of the grain boundary sliding and the overall deformation of specimens were measured successfully by the thermostable moiré method at a high temperature under load. (2) The effect of θ on the grain boundary sliding behavior was investigated. At θ=60°, the most uniform sliding distribution and the maximum initial rate of sliding are measured. (3) The deformation mode in the vicinity of the grain boundary is different from that of the other region far from the grain boundary. In the region of grain boundary migration, the normal strain is very large and the rotation with small shear strain is observed.

Observation of Grain Boundary Sliding of Aluminum Bicrystals by Thermostable Moiré Method

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