Development of Micro-indentation Tool for In-situ Mechanical Testing under Microwave Fields
[Technical Report, Technical Report]
CCDC Army Research Laboratory
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A novel in-situ indentation technique was developed to study mechanical properties of materials under 2.45-GHz single-mode microwave MW fields. The ultimate goal of the investigation was to establish viability of the application of MW fields to a two-phase material, where one phase was an MW susceptor, and the matrix was transparent to the MW field. In this scenario, the hypothesis was that the stress associated with the coefficient of thermal expansion mismatch between the second phase particle and the matrix will yield better toughness properties. A Knoop indenter and sample loading assembly were designed to indent samples at high temperatures under MW fields, yielding a first system of its kind. Several indentation tests were performed on conventionally sintered alumina Al2O310 wt nickel ferrite NiFe2O4. A sample loading procedure and an indentation testing procedure under MW fields were established. For the first time, in-situ indentation was achieved at temperatures up to 400 deg C under a 2.45-GHz single-mode MW field. A comparison was made of indentations under no applied field and progressively increasing fields resulting in increased sample temperatures at 100 H-field conditions. Knoop hardness and toughness of Al2O310 wt NiFe2O4 composites were compared with and without the application of MW fields. The designed system can be used for other applications, such as investigation of mechanical properties of ceramic materials at high temperatures.
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