Grain Size (Fine or Coarse)

"Although a wide-variety of international standards exist1, ASTM E112 is the dominant standard that grains are analyzed under in North and South America. In former times, and even still in practice today, most quality-control laboratories would analyze grains via the "Chart Comparison" method. Here, operators perform a visual estimation of the grain size by comparing a live image under an optical microscope to a micrograph chart, often posted on the wall near the microscope.

Example of a microscope eyepiece reticle used to compare against a live image.

Or, instead of comparing to a micrograph poster, one can insert an eyepiece reticle containing images of predefined grain size patterns, directly into the microscope's optical path. This way, the comparison is performed directly in the microscope, where the operator can see both the sample at question as well as a "golden" image simultaneously."

http://www.olympus-ims.com/en/applications/grain-size-analysis/

"If you have a pure piece of metal, you can control the size of the grains by heat treatment or by working the metal.

Heating a metal tends to shake the atoms into a more regular arrangement - decreasing the number of grain boundaries, and so making the metal softer. Banging the metal around when it is cold tends to produce lots of small grains. Cold working therefore makes a metal harder. To restore its workability, you would need to reheat it.

You can also break up the regular arrangement of the atoms by inserting atoms of a slightly different size into the structure. Alloys such as brass (a mixture of copper and zinc) are harder than the original metals because the irregularity in the structure helps to stop rows of atoms from slipping over each other."

http://www.chemguide.co.uk/atoms/structures/metals.html