Glossary of terms relating to powders
1981 Edition

According to IS 4124, powder consists of dry particles with a maximum dimension of 1000 micrometers. Particle size refers to the largest dimension of individual particles and is typically expressed in microns. Particle shapes are categorized as spherical (smooth and round), irregular (non-uniform with rough surfaces), angular (featuring sharp edges), and flaky or plate-like (thin and flat). These standardized definitions help maintain consistency within the metallic and non-metallic powder industries. Common particle size classifications include granules (>1000 µm), coarse powder (100–1000 µm), medium powder (10–100 µm), and fine powder (<10 µm).

IS 4124 describes flowability as the ability of powder to flow under specified conditions, influenced by factors such as particle size, shape, moisture content, and cohesion. Apparent powder density is defined as the ratio of the powder's mass to the volume it occupies under stated conditions, including the spaces between particles. Bulk density specifically refers to the apparent density of powder when freely poured into a container without compaction. Measurements are conducted under controlled conditions to ensure repeatability, typically using flow tests for flowability and volume/mass measurements for densities.

IS 4124 standardizes terminology for powder processing techniques including pressing, sintering, and warm pressing. 'Pressing' refers to compacting powder under pressure within a mold or die to form a specific shape. 'Sintering' is the process of heat bonding compacted powder particles below their melting point to fuse them together. 'Warm pressing' denotes pressing performed at temperatures above room temperature but below the sintering temperature, enhancing compaction without reaching full sintering. These terms are defined to ensure uniform understanding in powder metallurgy.

IS 4124 classifies fines (also called undersize) as the fraction of powder particles that pass through a specified sieve aperture, meaning they are smaller than that opening. Oversize particles are those that do not pass through the sieve and are larger than the aperture. Classification refers broadly to grading powders based on particle size, shape, or density to categorize material fractions. These definitions promote clarity in particle size distribution and sorting within powder engineering.

Key parameters defined in IS 4124 for evaluating powder surface area and porosity include Specific Surface, which quantifies surface area per unit mass (expressed in cm²/g or m²/g), Permeability Surface Area derived from permeability tests revealing pore connectivity, Calculated Surface Area estimated from particle size and shape data, and Adsorption Surface Area measured via gas adsorption techniques like BET to assess micro-porosity. Collectively, these parameters provide a comprehensive understanding of powder surface characteristics and internal pore structure.