Orientierungsabhängigkeit und Größeneffekte bei der Nanoindentierung von Einkristallen

Simple cubic (NiAl), body-centered cubic (Fe-3%Si) and face-centered cubic (copper) single crystals of the orientations (001), (011), (111) and (112) as well as hexagonal magnesium samples with (0001)- and orthogonal oriented grains were produced, prepared and investigated by the means of a nano-hardness measurement system (Hysitron TriboScope). Hardness indents of different depths were performed and the hardness and Young’s modulus were determined for each one. The topologies of selected large indents were measured and visualized using atomic force microscopy. For three of the samples (copper (001), (011) und (111)), a crystal plasticity elasto-plastic FEM simulation of the nano-hardness indentation experiment was performed. The measured Young’s modulus values of all samples were independent of the indentation depth and – with the exception of the magnesium samples – also of the sample orientation. For the Fe-3%Si and copper samples a clear indentation size effect (ISE) – an increase of the measured hardness with decreasing indentation depth – could be observed for all sample orientations. For samples made from NiAl and magnesium this size effect could not be shown. Instead, for these materials (NiAl, magnesium) the measured hardness value varied depending on the sample orientation. Furthermore, for the Fe-3%Si samples a different hardness value of the (001) orientation compared to the other investigated sample orientations was observed. In contrast to this all orientations of the copper samples show matching hardness values. An explanation for the appearance of an ISE in copper and Fe-3%Si and the absence of the ISE in NiAl and magnesium samples could not be found. All copper, Fe-3%Si, and magnesium samples showed strong pile-up effects around the hardness indent made visible using atomic force microscopy. This effect could not be found on the NiAl samples, though. The appearance of this effect in the body-centered and face-centered cubic as well as the hexagonal crystal system could be explained with the activation of primary glide systems, the material transport along the gliding plains, and the pile-up of sample material on the cutting line of the sample surface and the gliding plain. Furthermore, from the pile-up structures on the Fe-3%Si samples an activation of the gliding system {112}<111> could be deduced. The results of the FEM simulation showed excellent agreement with the atomic force microscopy images of the corresponding (001), (011) and (111) copper samples and thereby confirms the model of material transport along primary gliding systems. No explanation could be found for the absence of this effect in the simple cubic NiAl samples.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2008

Author dc:creator

• Klüber, Christian

Contributors dc:contributor

• Raabe, Dierk

• info:eu-repo/classification/ddc/550
• Metallphysik
• Gitterbaufehler
• Kristallgitter
• Kristallorientierung
• Härteeindruck
• Size-Effekt
• Einkristall
• Finite-Elemente-Methode
• Geowissenschaften
• Nanoindentierung
• Orientierungsabhängigkeit
• Größeneffekt
• Nanoindentation
• Single crystal
• Size effect
• crystallographic orientation
• FEM

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-112459%22

OAI record oai:identifier

https://publications.rwth-aachen.de/oai2d?verb=GetRecord&metadataPrefix=oai_dc&identifier=oai%3Apublications.rwth-aachen.de%3A49891