1) Materials science 
Microstructure is defined as the structure of a prepared surface or thin foil of material as revealed by a microscope above 25× magnification. The microstructure of a material (which can be broadly classified into metallic, polymeric, ceramic and composite) can strongly influence physical properties such as strength, toughness, ductility, hardnes...
the structural features of an alloy that are subject to observation under a microscope.
the structural features of an alloy that are subject to observation under a microscope.
<microscopy> The structure or texture of a suitably prepared specimen as revealed by a microscope. ... See: structure, morphology. ... (05 Aug 1998) ... 
Structure of the phases in a material. Can only be seen with an optical or electron mircoscope.
The structure of a prepared surface of a metal as revealed by a microscope at a magnification greater than ten diameters.The structure of polished and etched metal and alloy specimens as revealed by the microscope.
The structural features of an alloy that are subject to observation under a microscope. See also: Macrostructure.
the crystalline constituents of steel observed through a microscope
The structure of polished and etched metal and alloy specimens, as revealed by the microscope at magnifications over 10 diameters.
The structure of a prepared surface of a metal as revealed by a microscope at a magnification greater than ten diameters.