Grain Size Analysis

The inner structure of a metal is made up of individual crystalline areas known as “grains”. The material composition and manufacturing procedures (e. g. forging, casting or additive manufacturing) will influence the structure, size and orientation of these grains. The size, orientation and other structural characteristics of grains are directly linked to the mechanical and technological properties of these materials. So reliable analysis of grain sizes plays an important role in evaluation of structures and mechanical properties of various metallic materials.

Generally, the grain size is expressed with a grain size number in a standard diagram compliant with industrial standards. The standard grain size is divided into 12 grades, 1-4 grade is coarse grain, 5-8 grade is fine grain, and 9-12 grade is ultra-fine grain size. The smaller the grain size is, the better mechanical properties of the materials.

STEMart conducts grain size analysis on metal and alloy samples to evaluate the mechanical properties of the sample and investigate the causes of possible material failures. In addition, this test is also suitable for nonmetallic materials whose structures having appearances similar to those of the metallic structures.

Test Methods

• Visual comparison method
  • Visual comparison using standard diagrams: Visually compare the metal structure sample magnified with a microscope against the standard diagram to estimate the grain size number.
  • Visual comparison using grain size charts: A grain size chart for an ocular lens, in which an image of the grain size pattern is inserted, is used with a metallurgical microscope to enable visual inspection with both the magnified sample and the standard diagram in the field of view.
• Planimetric method: Calculate the number of grains in a known area, and then use the number of grains per unit area to determine the grain size level.
• Intercept method: Calculate the number of intercepts at the intersection of a test line segment (or network) of known length with the grain interface, and then use the intercept per unit length to determine the grain size level.

For more information about our grain size analysis services, please contact us.