The 13th Global Conference on
Materials Science and Engineering (CMSE 2024)

Abstract: Some materials take place in class of advanced smart materials, by exhibiting a peculiar property called shape memory effect. These alloys have dual characteristics called thermoelasticity and superelasticity, from viewpoint of memory behavior. Shape memory effect is initiated on cooling and deformation processes and performed thermally on heating and cooling, with which shape of materials cycles between original and deformed shapes in reversible way. Therefore, this behavior can be called thermal memory or thermoelasticity. Superelasticity is performed with stressing and releasing the material in elasticity limit at a constant temperature in the parent phase region, and shape recovery occurs instantly upon releasing. These phenomena are result of crystallographic transformations called martensitic transformation.

Thermoelasticity is governed by the thermal and stress induced martensitic transformation. Thermal induced martensite occurs on cooling 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 with deformation by means of stress induced transformation. Lattice twinning occurs in <110 > -type directions on the {110}-type plane of austenite matrix in self-accommodating manner. Superelasticity is also 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 metastable β-phase region, which has bcc-based structures. Lattice invariant shear and twinning is not uniform in these alloys and gives rise to the formation of complex layered structures, depending on the stacking sequences on the close-packed planes of the ordered parent phase 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. The unit cell and periodicity are completed through 18 layers in direction z, in case of 18R martensite, and unit cells are not periodic in short range in direction z.

In the present contribution, x-ray diffraction and transmission electron microscopy (TEM) studies were carried out on copper based CuAlMn and CuZnAl alloys. X-ray diffraction profiles and electron diffraction patterns exhibit super lattice reflections. X-ray diffractograms taken in a long-time interval show that diffraction angles and intensities of diffraction peaks change with the aging duration at room temperature. This result refers to the rearrangement of atoms in diffusive manner.

Keywords: Shape memory effect, martensitic transformation, thermoelasticity, superelasticity, lattice twinning, detwinning.

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 80 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 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 over 120 Virtual/Webinar Conferences, due to the coronavirus outbreak in three year of his retirement, 2020 and 2022.

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.

Scientific fields: 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.