Search

It is very important to estimate the deformation of polycrystalline materials from the elasto-plastic behavior of a single crystal. But this estimation is the difficult problem because the grain boundaries restrict the deformation in polycrystalline metals. In the recent investigations on this problem, the coarse-grained specimens of aluminum are used and many results are published, but up to now, the effect of grain boundary is not obvious. Then, in this paper, the bicrystal specimens of highly pure aluminum are adopted to analyse the effect of grain boundary on deformation behavior. The specimens have the grain boundaries perpendicular to the tensile axis and consist of two isoaxial crystals. On these specimens the stress-strain curves and the patterns of slip lines are obtained, and more, the moiré technique is applied to analyse the strain distribution. The results obtained are as follows. 1) The strain becomes more tightly restricted by the grain boundary with the increase of misorientation between primary slip systems. 2) The minimum value of strain near grain boundary becomes smaller as the misorient­ation between primary slip systems increases. 3) When the misorientation between primary slip systems is small, primary slip occurs across the grain boundary, but when the misorientation is big enough, it is hardly possible that each primary slip simultaneously occurs near grain boundary.

In the study of deformation behavior of metals, it is a very important problem to know the changes of its micro structure. There are many studies about the analysis of X-ray profile for the plastically deformed metals in fatigue test, but little in static test. Then in this paper the changes of micro structure of plastically deformed α-brass with two kinds of grain size was studied using the method by Warren and Averbach. The results obtained are summarized as follows.1) The micro strain is increased with increase of the tensile strain and in fine grain size the degree of increase is higher than that for coarse grain size. The distribution of micro strain is more ununiform in fine grain size.2) The particle size is decreased rapidly in the beginning of deformation and gradually after that. Also, the particle size is approached to about 200 Å in the diameter without any effects of grain size.3) The dislocation density is increased from 10¹⁰cm⁻² to 10¹¹cm⁻², then in fine grain size the degree of increase is higher than in coarse grain size.