Determination of the strain-rate sensitivity of ultrafine-grained materials by spherical nanoindentation. Issue 8 (6th March 2017)

• Record Type: Journal Article
• Authors: Feldner, Patrick; Merle, Benoit; Göken, Mathias
• Is Part Of: Journal of materials research. Volume 32:Issue 8(2017)
• Page Start: 1466
• Page End: 1473
• Publication Date: 2017-03-06
• Subjects: nanoindentation, -- spherical indentation, -- strain-rate sensitivity, -- ultrafine-grained material; Materials -- Research -- Periodicals; 620.1105
• DOI: 10.1557/jmr.2017.69
• Languages: English
• ISSNs: 0884-2914

Abstract

Abstract: Abstract : The strain-rate sensitivity of the flow stress represents a crucial parameter for characterizing the deformation kinetics of a material. In this work a new method was developed and validated for determining the local strain-rate sensitivity of the flow stress at different plastic strains. The approach is based on spherical nanoindentation strain-rate jump tests during one deformation experiment. In the case of ultrafine-grained Al and ultrafine-grained Cu good agreement between this technique and macroscopic compression tests has been achieved. In contrast to this, individual spherical nanoindentation experiments at constant strain-rates resulted in unrealistically high strain-rate sensitivities for both materials because of drift influences. Microstructural investigations of the residual spherical imprints on ultrafine-grained Al and ultrafine-grained Cu revealed significant differences regarding the deformation structure. For ultrafine-grained Cu considerably less activity of grain boundary sliding has been observed compared to ultrafine-grained Al.