Scientific Committee

Biography

Dr. Osman Adiguzel graduated from the Department of Physics, Ankara University, Turkey in 1974 and received a Ph.D.- degree from Dicle University, Diyarbakir-Turkey. He studied at Surrey University, Guildford, UK, as a post-doctoral research scientist from 1986-1987, and his studies focused on shape memory alloys. He worked as a research assistant, from 1975-80, at Dicle University and shifted to Firat University in 1980. He became a professor in 1996, and he retired due to the age limit of 67, following academic life of 45 years.

He published over 80 papers in international and national journals; He joined over 120 conferences and symposia at the international and national level as Plenary Speaker, Keynote Speaker, Invited speaker, speaker, or Poster presenter. He served as the program chair or conference chair/co-chair in some of these activities. In particular, he joined in the last six years (2014 - 2019) over 60 conferences as Speaker, Keynote Speaker, and Conference Co-Chair organized by different companies in different countries.

Additionally, he retired at the end of November 2019, and contributed with Keynote/Plenary Speeches at over 120 Virtual/Webinar Conferences, due to the coronavirus outbreak within three years of his retirement, in 2020 and 2022.

Dr. Adiguzel served as his directorate of the Graduate School of Natural and Applied Sciences, Firat University from 1999-2004. He supervised 5 Ph.D.- theses and 3 M. Sc theses. He is also a technical committee member of many conferences. He received a certificate which is being awarded to him and his experimental group in recognition of the significant contribution of 2 patterns to the Powder Diffraction File – Release 2000. The ICDD (International Centre for Diffraction Data) also appreciates the cooperation of his group and interest in the Powder Diffraction File.

Scientific fields of Dr. Adiguzel:  Shape memory effect and displacive phase transformations in shape memory alloys and other alloys, molecular dynamics simulations, alloy modeling, electron microscopy, electron diffraction, x-ray diffraction, and crystallography.

Abstract

The shape memory effect is a peculiar property exhibited by a series of alloy systems, called shape memory alloys in the β-phase region with chemical compositions. These alloys are very sensitive to external conditions, and phase structures turn into other crystal structures with the variation of temperature and stress with the movement of atoms on the crystal planes. Lattice vibrations (phonons), atomic bonds, grain boundaries, and interatomic interactions play an important role in the processing of transformation. This phenomenon is initiated with thermomechanical treatment on cooling and deformation and performed thermally on heating and cooling, with which the shape of material cycles between the original and deformed shape in a reversible way. Therefore, this behavior is called thermoelasticity. This behavior is the result of stimulus-induced phase transformations and thermal and stress-induced martensitic transformations. Thermal-induced martensitic transformations occur with cooperative movements of atoms by means of lattice invariant shear in <110 > -type directions on the {110} - type planes of austenite matrix and ordered parent phase structures turn into twinned martensite structures.  The twinned structures turn into detwinned martensite structures by means of stress-induced transformation by stressing the material in the martensitic condition. Superelasticity is also a result of the stress-induced martensitic transformation and the ordered parent phase of the alloy turns into the detwinned martensitic structure with stressing.   These alloys exhibit another property called superelasticity, which is performed with stressing and releasing at a constant temperature in the parent phase region, and shape recovery is performed instantly upon releasing the applied stress, by exhibiting elastic material behavior. Superelasticity is governed by stress-induced martensitic transformation and ordered parent phase structures turn into detwinned martensite structures with stressing.

Copper-based alloys exhibit this property in the metastable beta-phase regions, which have bcc-based structures. Lattice invariant shear and lattice twinning are not uniform in these alloys and cause to the formation of complex layered structures, depending on the stacking sequences on the close-packed planes of the ordered lattice. The layered structures can be described by different unit cells as 3R, 9R, or 18R depending on the stacking sequences on the close-packed planes of the ordered lattice.

In the present contribution; x-ray and electron diffraction studies were carried out on two solution-treated copper-based CuZnAl and CuAlMn alloys. Electron and x-ray diffraction exhibit superlattice reflections. Specimens of these alloys were aged at room temperature, at which both alloys are in a martensitic state, and a series of x-ray diffractions were taken at different stages of aging in a long-term interval. X-Ray diffraction profiles taken from the aged specimens in martensitic conditions reveal that crystal structures of alloys change in a diffusive manner, and this result refers to the stabilization.