BS ISO 18550:2016 pdf download

BS ISO 18550:2016 pdf download.Fine ceramics (advanced ceramics, advanced technical ceramics) — Testing method for macro-heterogeneity in microstructure
1 Scope
This International Standard specifies a test method for determining macro-heterogeneities within the microstructure of fine ceramics that are above a certain size within the volume of the material and affect materials mechanical strength properties. This method is limited to fine ceramics with a porosity of less than 10 vol% and that are transparent for visible light in the form of a thin specimen.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 coarse macro-heterogeneity
macro-heterogeneity, e.g. agglomerates, pores, inclusion, grains, with a size above 10 μm significantly affecting the mechanical strength
3.2 coarse macro-heterogeneity distribution
size distribution of coarse macro-heterogeneities
3.3 equivalent circle diameter
diameter of a circle having the same area as the coarse macro-heterogeneity
4 Principle
A variety of ceramics are composed of transparent materials and their macro-heterogeneity is observed in the transmission mode on a thin specimen.
5 Apparatus
5.1 Microscope, enabling the observation in the transmission mode. The microscope shall have a maximum magnification of the objective lens of ×10 and an illumination system with an adjustable aperture. A certified graticule shall be used for the calibration of the magnification.
5.2 Cutting machine, suitable machine capable of cutting the ceramics.
5.3 Grinding machine, suitable machine capable of grinding the ceramics.
6 Test specimen
The specimen shall be thin enough for observation in the transmission mode of the microscope. The typical thickness depends on the material and its porosity, and is between 30 μm and 200 μm. The specimen shall be prepared as follows. a) Cut a thin slab from the ceramic using a cutting machine. A thickness of the slab of more than 1 mm plus the final thickness is recommended. For a ceramic with thickness of less than 2 mm, this process can be omitted. b) One face of the slab shall be ground using a grinding machine and polished with a polishing machine by using polishing grains of a sequence of decreasing sizes with the finishing grit size of less than 1 μm. c) The other face of the slab shall be ground to adjust the thickness of the slab appropriately. Finally, the ground face shall be polished with the polishing machine by using polishing grains of a sequence of decreasing sizes as mentioned above to prepare a thin specimen for observation. d) Finally, mount the thin specimen on the microscope slide for observation. Transparent thermoplastic resin is recommended for mounting. e) The thickness of the specimen must be adjusted for adequate transparency before examination. With a specimen of adequate transparency, defects located at any depth in the specimen can be well focused. Scratches on both front and back surfaces are conveniently used to examine the applicability of this International Standard. If they are clearly seen from the opposite side, this International Standard can be applied.