Mitsuo Obata1 and Heihachi Shimada1
1Department of Metal Processing and Mechanical Metallurgy, Faculty of Engineering, Tohoku University, Sendai
The grain boundary sliding and the deformation in the vicinity of the grain boundary were studied at a high temperature by the moir´e 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°ree, 45°ree, or 60°ree 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 moir´e method was improved by the authors. According to the improved system, two families of moir´e 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 moir´e method at a high temperature under load.
(2) The effect of θ on the grain boundary sliding behavior was investigated. At θ=60°ree, 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.
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