Metallography and Microscopy: Reading Microstructure Correctly
Sampling, preparation, contrast and interpretation for optical, electron and orientation-based microscopy.
Preparation creates the evidence
Sectioning, mounting, grinding, polishing and etching must reveal structure without creating misleading damage. Smearing, pull-out, rounding and relief can imitate real features.
Optical microscopy
Optical methods provide rapid context for grains, phases, inclusions and processing defects. Contrast may come from etching, polarised light or differential interference.
Electron microscopy
Scanning electron microscopy extends resolution and depth of field. Secondary electrons emphasise topography; backscattered electrons provide atomic-number contrast; microanalysis adds local chemistry.
Orientation mapping
Electron backscatter diffraction maps crystal orientation, grain boundaries, texture and local misorientation. Good indexing depends on surface quality and appropriate step size.
Working rule
Interpret every image alongside preparation history, imaging mode, scale and sampling location. A striking micrograph is not automatically representative.