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Hardness–Grain‐Size Relations in Ceramics
Author(s) -
Rice Roy W.,
Wu Carl Cm.,
Boichelt Fred
Publication year - 1994
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1994.tb04641.x
Subject(s) - knoop hardness test , materials science , grain size , vickers hardness test , grain boundary , mineralogy , indentation , crystal (programming language) , ceramic , impurity , indentation hardness , crystallography , analytical chemistry (journal) , composite material , chemistry , microstructure , organic chemistry , chromatography , computer science , programming language
Both Vickers and Knoop hardness ( H ), measured at two or more loads in the range of 100–2000 g (most commonly 100 and 500 g) for a variety of dense oxide and non‐oxide materials, covering a range of grain sizes ( G ), including single crystals where possible, were shown to generally be consistent with (often more limited) literature data. Apparently, conflicting trends of H (1) showing either no G dependence, (2) decreasing from single‐crystal or large G values with decreasing G , or (3) having the generally accepted increase with decreasing G are shown to be due to the combination of the limited extent of data and H generally heing determined by two basic trends. These two trends are (a) the normal inverse G (i.e., H–G −1/2 ) dependence at finer G , (b) a variable G minimum at intermediate G , and (c) H increasing with increasing G at larger G (to. single‐crystal values). The H minimum is due to local cracking around the indent (mostly along grain boundaries), generally reaching a maximum effect, e.g., minimum in H , when the indent and grain sizes are similar, and tends to be greater for Vickers vs Knoop indents, higher loads and probably greater grain boundary Impurity, additive contents, and stresses.