Publications de Robert Schaller

MECHANICAL SPECTROSCOPY OF ORDERED BINARY Au-Cu

Robert Schaller, Daniele Mari, Iva Tkalcec Vâju

We have studied a binary Au-Cu single crystal by mechanical spectroscopy. Upon very slow cooling from high temperatures, additional relaxation peaks arise at lower frequencies in isothermal spectra after the disappearing of the Zener peak below 665 K due t ...

Polska Akad Nauk, Polish Acad Sciences, Inst Metall & Mater Sci Pas2015

Grain boundary relaxation in yellow gold bi-crystals

Robert Schaller, Daniele Mari, Iva Tkalcec Vâju, Ann-Kathrin Audren

The mechanical loss spectrum of a yellow gold bi-crystal is presented and analyzed in detail. The relaxation strength is monitored as a function of several geometrical parameters such as sample width, length and thickness. It is found that the relaxation s ...

Elsevier2015

GRAIN BOUNDARY RELAXATION IN Bi-CRYSTALS: MECHANICAL SPECTROSCOPY AND MOLECULAR DYNAMICS SIMULATIONS

Robert Schaller, Daniele Mari, Iva Tkalcec Vâju, Ann-Kathrin Audren

Different Au-Ag-Cu samples have been studied by mechanical spectroscopy. Both polycrystals and bi-crystals show a relaxation peak at 800 K, accompanied by an elastic modulus change. Since this peak is absent in single crystals it is related to the presence ...

Polska Akad Nauk, Polish Acad Sciences, Inst Metall & Mater Sci Pas2015

Applications Of Mechanical Spectroscopy To Industrial Materials

Robert Schaller

The paper is a review of original results, which were obtained by mechanical spectroscopy in the development of industrial materials, such as grey cast iron (damping capacity), aluminum alloys (recrystallization), nickel alloys (grain boundary embrittlemen ...

Polska Akad Nauk, Polish Acad Sciences, Inst Metall & Mater Sci Pas2015

High/room temperature mechanical properties of 3Y-TZP/CNTs composites

Robert Schaller, Mehdi Mazaheri

Spark Plasma Sintering (SPS) method was practiced, in the current investigation, to obtain fully dense materials with an excellent dispersion of MWCNTs (Multi-walled Carbon Nanotubes) within the matrix. Scanning and transmission electron microscopy microgr ...

Elsevier Sci Ltd2014

Theoretical modelling of grain boundary anelastic relaxations

Robert Schaller, Daniele Mari, Iva Tkalcec Vâju, Ann-Kathrin Audren

Grain boundary stress relaxation in Au polycrystals and single crystals has been studied by mechanical spectroscopy. A relaxation peak related to grain boundaries is observed at 620 K. Molecular dynamics simulations on Au are performed in order to illustra ...

Pergamon-Elsevier Science Ltd2014

Recrystallization and grain boundary formation in an 18-carat gold alloy studied by mechanical spectroscopy

Robert Schaller, Daniele Mari, Iva Tkalcec Vâju, Ann-Kathrin Audren

Heavily deformed 18-carat yellow gold samples show a recrystallization peak at 700 K during the first heating. The mechanical loss spectrum of polycrystals shows a relaxation peak at about 780 K, which is absent in single crystals made from the same alloy. ...

Trans Tech Publications Ltd2013

New In-Pd mechanical loss peak in ternary gold alloys

Robert Schaller, Daniele Mari, Iva Tkalcec Vâju, Ann-Kathrin Audren

A point defect relaxation peak has been observed in a ternary 18-carat gold alloy with the composition Au62.5Pd32.5In5. It shows a Curie Weiss dependence on the temperature, as is commonly observed for a Zener peak. However, the peak is absent in the binar ...

Pergamon-Elsevier Science Ltd2013

Grain boundary formation stages in a deformed yellow gold single crystal studied by mechanical spectroscopy

Robert Schaller, Daniele Mari, Iva Tkalcec Vâju, Ann-Kathrin Audren

A monocrystalline 18-carat yellow gold sample is deformed stepwise from 2% to 12% at room temperature. The mechanical loss spectrum is recorded and analysed. At low deformations the exponential high temperature background increases. At a critical deformati ...

Elsevier Science Sa2013

Grain boundary relaxation and grain growth in 18-carat yellow gold alloy

Robert Schaller, Daniele Mari, Iva Tkalcec Vâju, Ann-Kathrin Audren

A high-temperature anelastic relaxation peak in the mechanical loss spectrum of 18-carat yellow gold polycrystals is analysed and interpreted as due to grain boundary sliding accommodated predominantly by elastic deformation of the grains. The characterist ...

2012

Magnesium matrix composites as interesting HIDAMETS

Robert Schaller

Metal matrix composites, made of Mg or Mg-2wt.%Si matrices reinforced with C or SiC long fibres, were processed by gas-pressure infiltration. Such composites are an advantageous solution for developing light metallic materials, which exhibit simultaneously ...

2011

Multi-walled carbon nanotube/nanostructured zirconia composites: Outstanding mechanical properties in a wide range of temperature

Robert Schaller, Daniele Mari, Gilbert Fantozzi, Mehdi Mazaheri

Multi-walled carbon nanotube (MWCNT)/nanostructured zirconia composites with a homogenous distribution of different MWCNT quantities (ranging within 0.5-5 wt.%) were developed. By using Spark Plasma Sintering we succeeded in preserving the MWCNTs firmly at ...

Elsevier2011

High-Temperature Mechanical Spectroscopy of Nitrogen-Rich Ca-alpha-SiAlON Ceramics

Robert Schaller, Daniele Mari, Mehdi Mazaheri

Nitrogen-rich Ca-alpha-SiAlON ceramics made with different starting powder compositions have been studied by high-temperature mechanical spectroscopy in parallel with compressive deformation in a spark plasma sintering equipment. The mechanical loss spectr ...

2011

Thermal stress relaxation in magnesium matrix composites controlled by dislocation breakaway

Robert Schaller, Daniele Mari, Abu Salek Md. Fahim Chowdhury

In metal matrix composites (MMCs) thermal stress relaxation can be achieved either by interface debonding, crack propagation or by dislocation motion. The present paper shows that in the case of magnesium matrix, interface thermal stresses are relaxed by d ...

2010

The effect of the orientation of the basal plane on the mechanical loss in magnesium matrix composites studied by mechanical spectroscopy

Robert Schaller, Daniele Mari, Abu Salek Md. Fahim Chowdhury

In metal matrix composites, thermal stresses are relaxed by either interface debonding, crack propagation or dislocation motion. The present paper shows that in the case of a magnesium matrix, interface thermal stresses are relaxed by dislocation motion in ...

2010

Microstructures and mechanical properties of Al-base composite materials reinforced by Al-Cu-Fe particles

Joël Bonneville, Robert Schaller

In this study, we produced four composite materials with Al-based matrix reinforced by Al-Cu-Fe particles initially of the quasicrystalline (QC) phase. The processing route was a gas-pressure infiltration of QC particle preforms by molten commercial Al and ...

2010

Modulus anomaly in magnesium matrix composites

Robert Schaller, Daniele Mari, Abu Salek Md. Fahim Chowdhury

Several magnesium matrix composites were investigated by means of mechanical spectroscopy. A modulus anomaly has been observed in the composites reinforced with fibers while the phenomenon does not occur with particles. This effect is attributed to bonding ...

Wiley2010

High temperature mechanical spectroscopy of yttria stabilized zirconia reinforced with carbon nanotubes

Robert Schaller, Daniele Mari, Mehdi Mazaheri

High temperature mechanical properties of zirconia reinforced with carbon-nanotubes (CNTs) are studied by mechanical spectroscopy. CNTs limit zirconia grain-boundary sliding (GBS) and consequently deformation. Concurrent grain-growth and plastic deformatio ...

Wiley2010

High-temperature mechanical loss and creep behavior of fine-grained zirconia-containing nano-sized reinforcements

Robert Schaller, Claudia Ionascu

Polycrystalline zirconia (3Y-TZP grade) specimens unreinforced and reinforced with multiwalled carbon nanotubes (MWCNTs) or silicon carbide whiskers (SiCws) were processed by powder metallurgy and studied by mechanical spectroscopy. The high-temperature me ...

2009

High temperature mechanical spectroscopy of fine-grained ceramics

Robert Schaller, Claudia Ionascu

Mechanical loss measurements were performed at high temperature in fine-grained ceramics, such as zirconia and alumina. At high temperature, the mechanical loss increases exponentially with temperature, which accounts for material creep. The results are an ...

2009