Abstract
THE lecturer said that his purpose was to give some account of researches in which he had been engaged for a good many years, dealing with the manner in which netals were built up and the manner in which their strucures allowed them to yield when they were compelled to change their shape by being overstrained. A piece of metal was not a homogeneous single thing; it was a collocation of grains or granules, which built it up just as granules of ice built up a glacier. The grains of metal were irregular in shape and unequal in size. Their existence was revealed by polishing and etching the surface of the metal and examining it under the microscope, when the grains could readily be distinguished by differences of texture, and the boundaries between them could be clearly traced. Investigation showed that each grain was, in fact, a separate crystal, and the irregular boundaries were due to casual inequalities in the rates at which the various crystals had grown during their formation, which might occur when the metal was solidifying from a fluid state, or when it passed in the solid state through certain temperatures at which re-crystallisation took place. Each grain might be regarded as composed of an immense number of molecular brickbats grouped in perfectly regular tactical formation, but the direction in which these brickbats were piled was different in different grains; hence on being etched the polished surface showed differences in texture and in behaviour as to reflecting light. Microscopic photographs illustrating these features in iron and other metals were exhibited.
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The Structure of Metals 1 . Nature 75, 472–473 (1907). https://doi.org/10.1038/075472a0
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DOI: https://doi.org/10.1038/075472a0