GB/T 45974-2025 Fine ceramics—Method for determination of grain size and size distribution

Scope

This document describes a manual measurement method for determining the grain size of fine ceramics by observing the microstructure photos of the grain boundaries after polishing and etching the samples. This method cannot obtain the true average grain size, but instead obtains a slightly smaller parameter, which depends on the method used to analyze the two-dimensional cross-sections. The relationship between the measurement results of this method and the actual grain size depends on the grain shape and the degree of anisotropy of the microstructure. This document includes two types of methods: Method A and Method B. **Method A** is the average linear intercept method, which is divided into Method A1 and Method A2. Method A1 is suitable for single-phase dense ceramics and ceramics with a volume fraction of the main crystal phase and glass grain boundaries less than about 5%, where the intercept count is sufficient. Method A2 is suitable for ceramics with a volume fraction of pores or second phases greater than about 5%, or ceramics with multiple main crystal phases, where it is necessary to measure the length of a single intercept and optionally determine the size distribution. Method A2 is based on calculating the average linear intercepts of pores or phases separately by distinguishing the microstructural differences between them. **Note**: ISO 13383-2 provides a method for determining the volume fraction of second phases. **Method B** is the average equivalent circular diameter method, which is suitable for determining the grain size, grain aspect ratio, and size distribution of all types of ceramic materials (whether there are second phases or not). Some users apply automatic or semi-automatic image analysis to microscopic photos or directly captured microstructural images, as long as the adopted technology simulates the manual method (see Chapters 4 and 8.4), which meets the requirements of this document. This document is applicable to the deter

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