Publications by Efthymios Polatidis

Bragg edge tomography characterization of additively manufactured 316L steel

Christian Leinenbach, Roland Logé, Nikola Kalentics, Efthymios Polatidis, Markus Strobl

In this work we perform a neutron Bragg edge tomography of stainless steel 316L additive manufacturing samples, one as built via standard laser powder bed fusion, and one using the novel three-dimensional (3D) laser shock peening technique. First, we consi ...

AMER PHYSICAL SOC2022

Tailored deformation behavior of 304L stainless steel through control of the crystallographic texture with laser-powder bed fusion

Christian Leinenbach, Roland Logé, Efthymios Polatidis, Markus Strobl

Laser-powder bed fusion (L-PBF) has gained significant research interest, not only for its profound advantage of producing near-net shape complex geometries of metallic parts, but also for the possibility of producing tailored microstructures. Here we expl ...

ELSEVIER SCI LTD2022

The effect of stress triaxiality on the phase transformation in transformation induced plasticity steels: Experimental investigation and modelling the transformation kinetics

Helena Van Swygenhoven, Efthymios Polatidis, Nicola Casati

In situ multiaxial loading during neutron diffraction tests were undertaken on a low-alloyed Quenched and Partitioning (Q&P) Transformation Induced Plasticity (TRIP) Bainitic Ferrite (TBF) steel with dispersed austenite particles. The effect of stress tria ...

2021

Characterization, mechanical properties and dimensional accuracy of a Zr-based bulk metallic glass manufactured via laser powder-bed fusion

Jamasp Jhabvala, Güven Kurtuldu, Steven Van Petegem, Antonia Neels, Roland Logé, Efthymios Polatidis, Navid Sohrabi, Annapaola Parrilli

Bulk metallic glasses (BMGs) are high-strength, highly elastic materials due to their disordered atomic structure. Because BMGs require sufficiently high cooling rates to bypass crystallization, laser-based additive manufacturing (AM) methods have recently ...

2020

Measurement and prediction of the transformation strain that controls ductility and toughness in advanced steels

Helena Van Swygenhoven, William Curtin, Francesco Maresca, Efthymios Polatidis

New-generation multi-phase martensitic steels derive their high strength from the body-centered cubic (BCC) phase and high toughness from transformation of the metastable face-centered cubic (FCC) austenite that transforms into martensite upon loading. In ...

PERGAMON-ELSEVIER SCIENCE LTD2020

Deformation mechanisms in a superelastic NiTi alloy: An in-situ high resolution digital image correlation study

Helena Van Swygenhoven, Efthymios Polatidis

An in-situ high resolution digital image correlation investigation during uniaxial tensile deformation reveals the recoverable and the non-recoverable strain mechanisms in a Ni51Ti49 alloy with a mean grain size of 35 mu m. Recoverable strain is due to the ...

2020

Neutron Diffraction and Diffraction Contrast Imaging for Mapping the TRIP Effect under Load Path Change

Helena Van Swygenhoven, Efthymios Polatidis, Markus Strobl

The transformation induced plasticity (TRIP) effect is investigated during a load path change using a cruciform sample. The transformation properties are followed by in-situ neutron diffraction derived from the central area of the cruciform sample. Additio ...

MDPI2020

A crystallographic extension to the Olson-Cohen model for predicting strain path dependence of martensitic transformation

Helena Van Swygenhoven, Efthymios Polatidis

A modification to the empirical Olson-Cohen strain-induced austenite to martensite transformation kinetic model is proposed. The proposed kinetic model accounts for the stress state at the grain level and the crystallography of the transformation mechanism ...

PERGAMON-ELSEVIER SCIENCE LTD2019

The interplay between deformation mechanisms in austenitic 304 steel during uniaxial and equibiaxial loading

Helena Van Swygenhoven, Wei-Neng Hsu, Efthymios Polatidis

The preferred deformation mechanisms with respect to the load path are studied in a medium stacking fault energy 304 austenitic stainless steel that exhibits both transformation induced plasticity and twinning induced plasticity. In situ neutron diffractio ...

2019

Following Microstructures during Deformation: In situ X-ray/Neutron Diffraction and HRDIC

Helena Van Swygenhoven, Efthymios Polatidis

The mechanical behavior of three engineering materials is studied employing in situ deformation methods. The study covers metastable austenitic steels with different stacking fault energies during multiaxial loading, a Ti-6Al-4V alloy processed by electron ...

IOP PUBLISHING LTD2019

Impact of in situ nanomechanics on physical metallurgy

Johann Michler, Helena Van Swygenhoven, Efthymios Polatidis

The mechanical response of modern alloys results from a complex interplay between existing microstructure and its evolution with time under stress. To unravel these processes, in situ approaches intrinsically have a critical advantage to explore the basic ...

2019

Deformation and degradation of superelastic NiTi under multiaxial loading

Helena Van Swygenhoven, Steven Van Petegem, Wei-Neng Hsu, Efthymios Polatidis, Nicola Casati

The degradation of the superelastic properties of a commercial NiTi alloy is studied during uniaxial, biaxial and load-path-change cycling performed in-situ with synchrotron X-ray diffraction. Careful examination of the diffraction pattern during uniaxial ...

2019

A High Resolution Digital Image Correlation Study under Multiaxial Loading

Helena Van Swygenhoven, Wei-Neng Hsu, Efthymios Polatidis

In this study, a miniaturized cruciform-shaped sample geometry which allows reaching high plastic strain under equibiaxial loading with reduced thickness at the test section is presented. The thinning method results in excellent surface quality that can be ...

SPRINGER2019

Load path change on superelastic NiTi alloys: In situ synchrotron XRD and SEM DIC

Helena Van Swygenhoven, Steven Van Petegem, Wei-Neng Hsu, Efthymios Polatidis, Nicola Casati

2018

Suppressed martensitic transformation under biaxial loading in low stacking fault energy metastable austenitic steels

Helena Van Swygenhoven, Wei-Neng Hsu, Efthymios Polatidis

2018