leometwu的部落格

       Untinted, colors produced  naturally. Specimen was from a ductile iron casting severely over-heated because of failure of the temperature controller. Incipient melting occurred, leaving a  honey-comb-shape white delineation of carbide on the grainboundaries. This shape has a special meaning----grains grow to their maxima, no more grain growth will continue.   Photo taken with ZEISS microscope--an amazing product from Germany.