Microstructural analysis of thermally induced and deformation induced martensitic transformations in Fe-12.5 wt.% Mn-5.5 wt.% Si-9 wt.% Cr-3.5 wt.% Ni alloy

WOS: 000234613600025Martensitic transformations induced by thermally and compression deformation at room temperature in Fe-12.5 wt.% Mn-5.5 wt.% Si-9 wt.% Cr-3.5 wt.% Ni alloy were studied in detail by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). From microstructural observations, it was seen that heat treated samples exhibited regular overlapping of stacking faults and epsilon martensite plates were formed parallel to each other. Also, TEM investigations showed that the orientation relationship between gamma (fcc) and epsilon (hcp) phases corresponds to Shoji-Nishiyama type. With applied low plastic deformation rate, only 8 martensite occurred in austenite grain. As a consequence, 4 and 25% plastic deformation at room temperature caused e martensite formation in austenite phase and the new epsilon (hcp) and alpha' (bcc) martensite formation in martensite phases, respectively. Orientation relationship between epsilon and alpha' phases was found by the electron diffraction analysis. (c) 2005 Elsevier B.V. All rights reserved

Effect of heat treatment on martensitic transformation in Fe-12.5 % Mn--5.5 % Si-9 % Cr-3-5 % Ni alloy

WOS: 000228253200002In this study, thermally-induced martensitic transformation (gamma(fcc) -> epsilon(hcp)) in Fe-12.5% Mn-5-5% Si-9% Cr-3-5% Ni (weight) alloy was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The effect of cooling rate was investigated. It was observed that fast cooled sample exhibited regular overlapping of stacking faults and epsilon martensite plates were formed parallel to each other. TEM investigations showed that the orientation relationship between gamma-epsilon phases corresponds to Shoji-Nishiyama type orientation relationship

Effects of deformation on microstructure and mechanical properties of a Cu-Al-Ni shape memory alloy

WOS: 000257053300013In Cu-11.92 wt.%Al-3.78 wt.%Ni shape memory alloy, the influence of deformation and thermal treatments on the microstructure and mechanical properties under the compression test were studied by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). Experiments show that the mechanical properties of the alloy can be enhanced by convenient heat treatments. The alloy exhibits good mechanical properties with high ultimate compression strength and ductility after annealing at high temperature. However, it exhibits brittle fracture and dramatic strain hardening, with linear stress-strain behavior after annealing at low temperature. The changes in the mechanical properties have been linked to the evolution of the degree of order, occurrence of precipitation, and variation of the grain size. From microstructural observations, it is seen that the beta(1)' (18R) and gamma(1)' (2H) martensite phases coexist at different fractions in the undeformed and deformed states. Deformation induces the changes between the beta(1)' and gamma(1)' martensites and deformation-induced martensites form at preferred orientations as mechanical twins. The beta(1)' martensite variants are twin-related with respect to the (128)(18R) mirror plane and a new orientation relationship for these twin variants is derived as (128)(A)parallel to (128)(C): [461](A)parallel to [461](C). Additionally, an increase in the amount of deformation causes martensite reorientation, de-twinning, and dislocation generation; also, the martensite plates are seen to have rearranged in the same orientation to be parallel with each other. (c) 2007 Elsevier Inc. All rights reserved

Influence of Mn content on the magnetic properties and microstructure in Fe-Mn-Mo alloys

WOS: 000273709600034The effects of the Mn content on the magnetic properties and microstructure of the Fe-Mn-Mo alloys have been investigated by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction, and Mossbauer spectroscopy. Experiments reveal that two types of thermal-induced martensites, epsilon (h.c.p.) and alpha' (b.c.c.) martensites, form in the as-quenched alloys and these transformations have athermal characters. epsilon and alpha' martensites coexist in the Fe-Mn-Mo alloys with 13.4-17.2 wt%Mn content. However, the Mn content affects considerably the amount of martensites and the amount of alpha' martensite decreases drastically while the amount of epsilon martensite increases with an increase in Mn content. Furthermore. only epsilon martensite appears in the case of 20.2 wt%Mn. Mossbauer spectra of the alloys reveal a paramagnetic character with a singlet for the gamma (f.c.c.) austenite and epsilon martensite phases and a ferromagnetic character with a broad sextet for alpha' martensite phase. With an increase in Mn content, the magnetic character of the Fe-Mn-Mo alloys changes and the ferromagnetic character disappears completely in the case of 20.2 wt%Mn. (C) 2009 Elsevier B.V. All rights reserved.Kirikkale University Scientific Research FundKirikkale University [2008/34, 2008/35]This study was supported by the Kirikkale University Scientific Research Fund with the project numbers 2008/34 and 2008/35

Effect of Mn content on the austenite-martensite phases and magnetic properties in Fe-Mn-Co alloys

WOS: 000295601700117The influence of the Mn content on the magnetic properties and microstructure of the Fe-Mn-Co alloys has been investigated by means of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Mossbauer spectroscopy. Experiments reveal that two types of thermal-induced martensites, epsilon (h.c.p.) and alpha' (b.c.c.) martensites, form in the as-quenched alloys. epsilon and alpha' martensites coexist in the Fe-Mn-Co alloys with 13.2-17.3 wt% Mn content while only epsilon martensite appears in the case of 20.7 wt% Mn. The amount of a' martensite decreases significantly while the amount oft martensite increases with an increase in Mn content. The lattice parameters of austenite increase also with increasing Mn content. In addition, Mossbauer spectra of the alloys reveal a paramagnetic character with a singlet for the gamma (f.c.c.) austenite and e martensite phases and a ferromagnetic character with a broad sextet for a' martensite phase. The magnetic character of the Fe-Mn-Co alloys changes as Mn content increases and the ferromagnetic character disappears completely in case of 20.7 wt% Mn. (C) 2011 Elsevier B.V. All rights reserved.Kirikkale UniversityKirikkale University [2008/34, 2008/35]This study was supported by the Kirikkale University Scientific Research Fund with the project numbers 2008/34 and 2008/35

The effects of austenite phase deformation on microstructure and magnetic properties in Fe-13.4% Mn-5.2% Mo alloy

WOS: 000292750000026The effects of austenite phase deformation on martensitic transformations and magnetic properties in Fe-13.4% Mn-5.2% Mo have been investigated by scanning electron microscopy, transmission electron microscopy, and Mossbauer Spectroscopy. The increase of plastic deformation rates on austenite phase created considerable changes in amounts of epsilon (h.c.p.) and alpha'(b.c.c.) martensite, and austenite grains size decreased. Analysis of microstructure and Mossbauer spectra show that the amount of e martensite increased at low deformation rates whereas it decreased at high deformation rate. Besides, Mossbauer spectra of the alloy reveal a ferromagnetic character with a broad sextet for alpha' martensite phase and a paramagnetic character with a singlet for the gamma (f.c.c.) austenite and epsilon martensite phases. In the other hand, the magnetic character of the alloy exhibits a different magnetic order depending on strain rates.Kirikkale UniversityKirikkale University [2008/34, 2008/35]This study was supported by the Kirikkale University Scientific Research Fund with the project numbers of 2008/34 and 2008/35

Comparison of thermally induced and deformation induced martensite in Fe-29% Ni-2% Mn alloy

WOS: 000248028300038The morphology and crystallography of maitensite either formed by cooling to subzero temperatures (thermal effect) or by compression deformation were compared for different austenite grain sizes of Fe-29% Ni-2% Mn alloy by transmission electron microscope (TEM). TEM observations revealed both epsilon and alpha' martensite formation within large grained austenite phases by thermal effect whereas only alpha' martensite formation was observed in small grained austenite phases. On the other hand, compression deformation effect caused only a' martensite formation in both small and large grained austenite phases of Fe-29% Ni-2% Mn alloy. Thermally induced alpha' martensite exhibited a lenticular morphology with partial twinnings that are peculiar to this kind of morphology. The crystallographic orientation relationship between austenite and thermally induced alpha' lenticular martensites was found to be as Kurdjumov-Sachs (K-S) type relationship. (c) 2006 Elsevier B.V. All rights reserved

The effect of the computer-based analogy used in science teaching on learning outcomes

The aim of this study is to examine the effects of computer-based analogy (CBA) used in science teaching in terms of the unit of Structure and Properties of Matter on seventh-grade students' academic success. The attitudes of students against science teaching lesson were also described in this study. This study was applied to 60 seventh-grade students from two different classes of the same teacher from a public school in Koprubasi/Trabzon. In the study, pre-test-post-test control group quasi-experimental research model was used. The remarks of the students were described by content analysis within the context of qualitative research method. During the research period, computer-based analogy method was applied to the experimental group; on the other hand, traditional teaching method was applied to the control group. In the study, quantitative data as data collection tool was collected through academic success test prepared by the researcher. On the other hand, qualitative data was collected through an interview form, including open-ended questions formed by consulting experts. The results of the study show that the computer-based analogy method is more effective than the present program applications in terms of students' academic success in science lessons and permanence of knowledge. The results of the qualitative data analysis show that the students had positive views related to the lesson made by the computer-based analogy method. © 2020 Ekip Buro Makineleri A

The effects of STEM education on scientific process skills and STEM awareness in simulation based inquiry learning environment

In this study, the effects of STEM education in the simulation-based inquiry learning (SBIL) environment on the students' scientific process skills and STEM awareness were investigated. In addition, the use of simulations in STEM education was discussed by evaluating students' views on activities. Study group of the research consists of 39 students enrolled in science teaching undergraduate program at a university in Turkey. Results of the study showed that STEM education performed in the SBIL environment has a positive effect on the development of scientific process skills and STEM awareness. The students expressed a positive opinion on the STEM education that it provided the development of scientific process skills and increased their attitude and motivation towards the course. The students stated that the simulation program used in the STEM activities provided important advantages such as designing and developing engineering products, experiments and reducing errors. © 2020 Ekip Buro Makineleri A

The effects of pre-strain, recovery temperature, and bending deformation on shape memory effect in an Fe-Mn-Si-Cr-Ni alloy

WOS: 000265911700042In this study, effects of pre-strain, recovery temperature, and number of bending test cycles on the microstructure and shape memory behavior of Fe-12.5%Mn-5.5%Si-9%Cr-3.5%Ni alloy have been investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM). X-Ray diffract-ion method, and bending test. Experiments show that the shape memory effect of the alloy can be enhanced by convenient recovery temperature and pre-strain rate. The shape recovery ratio increases with increasing pre-strain and recovery temperature, while it decreases with an increase in the number of bending test cycles. The changes in the shape memory are attributed to the variation of amount of epsilon martensite and crystal defects. The amount of epsilon martensite increases with increasing the pre-stain ratio. Crystal defects decrease with an increase in the recovery temperature, while they increase with increasing the number of the bending test cycles. (C) 2008 Elsevier B.V. All rights reserved