Abstract
It becomes important to measure mechanical properties of local area of materials because of downsizing of industrial materials, and the fracture of materials often starts at the nanoscale defects. Therefore, the measurement of hardness of the local area of materials is one of key technologies to develop new materials. Nanoindentation is the depth sensing indentation method and can measure the mechanical properties of nanoscale area of materials. The hardness of materials under the controlled environment like high temperature is a big issue in energy or environment industries. Therefore, it becomes important to measure high temperature mechanical properties of nanoscale area of materials by nanoindentation. However, the shape of indenter may change when an indenter contacts to the material surface at high temperatures, and the nanoindentation at high temperatures may lead to inaccuracy of measurements. Nanoindentation does not measure indented are directly but converts the indentation depth to the indented area by area function. In order to correctly convert the indentation depth to the indented area, it is necessary to derive the area function of indented area at high temperatures. In this report, the area function is proposed that considers the change of indenter shape during repeating contact at heated materials. By using this proposed area function, nanoindentation hardness and the reduced modulus of sapphire were obtained at 303K, 473K, 673K, 873K and 1073K successfully. The nanoindentation can be used at high temperatures, if this proposed area function is used.
Highlights
It becomes important to measure mechanical properties of local area of materials because of downsizing of industrial materials, and the fracture of materials often starts at the nanoscale defects
The conventional technique to measure the hardness of materials using an optical micrometer can evaluate mechanical properties of a local region over several μm according to the resolution of optical micrometer but cannot measure the hardness of nanoscale area
Even if the adhesion is avoided by the repeating contact, the change of indenter shape may occur by abrasion that becomes very severe at high temperature
Summary
It becomes important to measure mechanical properties of local area of materials because of downsizing of industrial materials, and the fracture of materials often starts at the nanoscale defects. M. Pharr proposed to measure the hardness by the depth sensing indentation method in 1992 without using an optical micrometer [1]. Pharr proposed to measure the hardness by the depth sensing indentation method in 1992 without using an optical micrometer [1] It becomes important to measure high temperature mechanical properties in nanoscale area of materials by nanoindentation. Even if the adhesion is avoided by the repeating contact, the change of indenter shape may occur by abrasion that becomes very severe at high temperature. The area function is proposed that considers the change of indenter shape during repeating contact at heated materials. By using the proposed area function, the high temperature hardness and reduced modulus of sapphire were measured
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