New Descriptor-Based Material Characterization Method Using Micro Compression Test on Spherical Microsamples

Abstract

A newly developed micro compression test on spherical samples was introduced as a fast mechanical material characterization method within a novel high-throughput alloy development process of structural materials. During the validation phase of the new micro compression test method, conventionally manufactured bearing balls with diameters of 0.6–1.0 mm were used. Microspheres of different rolling bearing steels, such as AISI 52100 (DIN 100Cr6) and AISI 420 (DIN X46Cr13), were therefore studied in detail. The micro compression test made possible an investigation of the elastic-plastic deformation behavior during loading and unloading of metallic microspheres. So-called descriptors were extracted from continuously measured force-displacement curves as fast characteristic values. When the geometry was taken into account, normalized descriptors enabled the comparison of different sample sizes. A wide database of 20 investigated metallic alloys in over 60 different heat treatment conditions showed the potential of the new mechanical characterization method, since changes in alloy composition and heat treatment were reflected with a high sensitivity by the descriptors of the micro compression test. Furthermore, recent results show that this test delivers robust descriptors regarding a possible material-specific scatter within a batch. Additional universal microhardness measurements, as well as x-ray diffraction investigations for obtaining the retained austenite content, enabled a detailed analysis and the validation of the descriptors. Although the main reason for the development of the micro compression test was initially based on a sustainable and resource-efficient high-throughput approach within the search for new alloy compositions, the results might be of great interest for the ASTM community regarding the potential material characterization of bearing balls.