Prof. Osman Adiguzel
Firat University, Turkey

Biography: Dr. Osman Adiguzel graduated from Department of Physics, Ankara University, Turkey in 1974 and received PhD- degree from Dicle University, Diyarbakir-Turkey. He studied at Surrey University, Guildford, UK, as a post doctoral research scientist in 1986-1987, and his studies focused on shape memory alloys. He worked as research assistant, 1975-80, at Dicle University and shifted to Firat University in 1980. He became professor in 1996, and he has been retired due to the age limit of 67; following academic life of 45 years.
He published over 60 papers in international and national journals; He joined over 120 conferences and symposia in international and national level as Plenary Speaker, Keynote Speaker, Invited speaker, speaker or Poster presenter. He served the program chair or conference chair/co-chair in some of these activities. In particular, he joined in last even years (2014 - 2020) over 80 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 to 12 Virtual/Webinar Conferences in the first year of his retirement, 2020.
Dr. Adiguzel served his directorate of Graduate School of Natural and Applied Sciences, Firat University in 1999-2004. He supervised 5 PhD- theses and 3 M.Sc theses. He is also Technical committee member of many conferences. He received a certificate which is being awarded to him and his experimental group in recognition of significant contribution of 2 patterns to the Powder Diffraction File – Release 2000. The ICDD (International Centre for Diffraction Data) also appreciates cooperation of his group and interest in Powder Diffraction File.
Speech Title: Shape Reversibility and Temperature Deformation Relation in Memory Behavior of Shape Memory Alloys
Speech Abstract: Shape memory effect is a temperature dependent phenomenon exhibited by certain alloy systems called shape memory alloys which take place in the class of smart and functional materials, with the response to the variation of temperature and external conditions. These alloys have dual characteristics called thermoelasticity and superelasticity. Shape memory effect is initiated by cooling and deformation and performed thermally on heating and cooling. Therefore, this behavior can be called thermoelasticity. This deformation is plastic deformation; strain energy is stored in material and released on heating by recovering original shape, and shape of material cycles in reversible way between deformed and original shape of material on cooling and heating. The origin of this phenomenon lies in the fact that the material changes its internal crystalline structure with changing temperature Thermoelasticity is governed by thermal and stress induced martensitic transformations on cooling and stressing.
Superelasticity is performed by stressing and releasing material in a constant temperature in parent phase region. For the Superelasticity, materials are stressed in the elasticity limit in the parent phase region and, shape recovery is performed instantly and simultaneously upon releasing the applied stress. Superelasticity is governed by stress induced transformation by stressing and releasing materials at a constant temperature in parent phase region. Parent austenite phase structures turn into the fully detwinned martensite structure with stressing by means of stress induced martensitic transformation, and the detwinned structures turn into parent phase structure upon releasing the stress. The crystal structure cycles between detwinned martensite structures and the parent phase structure by stressing and releasing, by exhibiting the elastic material behavior.
Thermal induced martensite occurs along with lattice twinning and ordered parent phase structures turn into twinned martensite structures by means of lattice invariant shears, and these structures turn into detwinned martensitic structures by means of stres induced transformation. Lattice twinning occurs in two opposite directions, <110 > -type directions on the {110}-type plane of austenite matrix in self-accommodating manner and consists of lattice twins.
Twinning and detwinning processes can be considered as elementary processes activated during the transformations. Shape memory effect is performed in a temperature interval after first cooling and stressing processe, whereas superelasticity is performed mechanically in a constant temperature in parent phase region, just over the austenite finish temperature. Deformation at different temperature exhibits different behavior beyond shape memory effect and superelasticity.
Copper based alloys exhibit this property in metastable beta-phase region, which has bcc based structures at high temperature parent phase field. Lattice invariant shear is 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.
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 super lattice reflections. Specimens of these alloys were aged at room temperature, 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 chance in diffusive manner, and this result refers to the stabilization.