Research report on metallographic preparation of composite materials- Trojan (Suzhou) material technology Co., Ltd.

Research report on metallographic preparation of composite materials

28-01-2023

Metal matrix composites (MMCs) are composites made of metal and its alloy as the matrix, artificially combined with one or several metal or non-metal reinforcing phases. Most of its reinforcing materials are inorganic non-metals, such as ceramics, carbon, graphite and boron, etc., and metal wires can also be used. It forms modern composite material systems together with polymer composites, ceramic matrix composites and carbon/carbon composites. Boroncarbide, also known as black diamond, is an inorganic compound. The chemical formula of it is B₄C. It is usually a gray-black micropowder, and is one of the three hardest known materials (after diamond and Cubic boron nitride) It is used in tank armor, body armor and many industrial applications. It has a Mohs hardness of about 9.5, and by laminating boron carbide ceramics in metal, the advantages of both metal and ceramic can be obtained.

01 Grinding
Grind the specimen with Alpha-600 automatic grinder&polisher，diamond grinding disc P400→P1500→P3000；

Alpha-600 automatic grinder&polisher

Diamond grinding disc

Equipment	Alpha-600 automatic grinder&polisher
Consumables	Diamond grinding disc：P400，P1500，P3000
Parameter	Pressure：15N，Speed：130rpm，TIime：2Min

02 Rough Polishing
Polish the specimen with Alpha-600 automatic grinder&polisher，use NL polishing cloth first, then use 3μm polycrystalline diamond suspension with colloidal silica suspension.

NL-CP white fiber polishing cloth

PD-W polycrystalline diamond suspension

Equipment	Alpha-600 automatic grinder&polisher
Consumables	NL polishing cloth，3μm polycrystalline diamond suspension, colloidal silica suspension
Parameter	Same direction：150rpm，Pressure：20N，Time: 300s

03 Fine polishing
Polish the specimen with Alpha-600 automatic grinder&polisher，use ET polishing cloth with 50nm colloidal silica suspension to do fine polishing.

ET-JP white synthetic velvet polishing cloth

SO T401 Colloidal silica suspension

Equipment	Alpha-600 automatic grinder&polisher
Consumables	ET polishing cloth，50nm colloidal silica suspension
Parameter	Same direction：120rpm，Pressure：10N，Time: 60s

04 Observation

Equipment	MN 60 series microscope
Parameter	50×→500×

05 Analysis

50X

500X

50X

500X

50X

500X

The hardness of Boroncarbide is very high, and it is difficult to grind with general silicon carbide abrasive paper, so diamond grinding discs are used for grinding.
Due to the disparity in hardness between the substrate and the conforming boron carbide phase, in order to prevent embossing, first use a hard lint-free woven cloth for rough polishing. For boron carbide, silicon dioxide should be used for mechanical chemical polishing to obtain a better polished surface.
It can be seen from the picture that the distribution of boron carbide in the L2 sample is uneven, and the fine particles are seriously aggregated in some areas.