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COB22 ASPECTOS FÍSICO-QUÍMICOS DA DECOMPOSIÇÃO SPINODAL bm ® bt OBSERVADA EM LIGA DE TITÂNIO BETA METAESTÁVEL/ PHYSICO-CHEMICAL ASPECTS OF THE SPINODAL DECOMPOSITION IN A BETA TITANIUM ALLOY
Ricardo Artur Sanguinetti Ferreira († ) & Elisabeth Gautier († † )
(† ) Departamento de Engenharia Mecânica da UFPE, Rua Acadêmico Hélio Ramos s/n - Cidade Universitária 50740-530 Recife - PE
e-mail : Sanguinetti@npd.ufpe.br
(† † ) Laboratoire de Science et Génie des Matériaux Métalliques - École des Mines de Nancy, Parc de Saurupt 54042, Nancy Cedex, France
A beta titanium alloy Ti-5.0Al-2.0Sn-4.0Zr-4.0Mo-2.0Cr-1.0Fe ( by weigth) was solution treated and followed by quenching. In the supersaturation condition this alloy was reheated at 0.5o C/s and 5.0o C/s in order to study the sequences of phase transformation on the anisothermal conditions. In the fisrt stages of heating, a little modification was observed on the morphology microstructures before the precipitation of intermediary phases. Different zones of the matrix present a darker contrast as a consequence of fluctuations in the chemical composition. Chemical microanalysis obtaineid by EDS in transmission electron microscopy revealed that those darker zones were weakened in Mo, Cr and Fe solute elements. Morphological analysis in electron microscopy revealed no interface between rich and poor zones of matrix. Electron diffraction patterns taken from it showed scattered spots in the same lattice. The results indicate that solute separation, has no interface and identical lattice for different zones, thus we conclude that spinodal decomposition occurs really in beta titanium alloy at low temperatures.
Keywords: Spinodal decomposition; Decomposition in b-Ti; Phase transformation in b-Ti; Decomposição spinodal
COB23 ESTUDO DA CINÉTICA DE CRESCIMENTO E DA ESTABILIZAÇÃO DE GRÃOS EM LIGAS DO SISTEMA CU-ZN-AL / THE STUDY OF THE KINETIC OF GROWTH TO STABILIZE THE GRAIN GROWTH IN THE CU-ZN-AL SYSTEM
Ricardo Artur Sanguinetti Ferreira († ), Paulo César Botelho de Andrade († † ) Severino L. Urtiga Filho(† ) e Ney F. de Quadros(† )
(† ) DEMEC - Departamento de Engenharia mecânica da Universidade Federal de Pernambuco - UFPE - Av Acadêmico Hélio Ramos s/n Cidade Universitária 50.741-530, Recife-PE. - E-mail : Sanguinetti@npd.ufpe.br
(† † ) ITEP- Instituto de Tecnologia do Estado de Pernambuco - Av. Prof. Luís Freire 700 Cidade Universitária 54.740-540, Recife-PE.
The study of the microstruture evolution is of fundamental importance for Cu-Zn-Al shape memory alloy. The growth of grain degrades the shape memory effect by the displacement of temperatures where the transformations are observed. The degradation can be softened by the control of grain boundary migration or precipitation as a consequence of the diffusion process. The process control can be obtained by the increase the activation energy, which is produced by addition of the alloy elements. In this study was used a Cu-Zn-Zn alloy without the addition of elements. Based on the area criterion of the ASTM standard, the statistic measurements of a grain size were made in samples treated at different temperature of the ageing or annealing treatments. The kinetic of the grain growth was studied by an Arrhenius empirical law and the activation energy for this process (EA) was estimated by ln (D) x 1/T diagram. At lower temperatures, results of the activation energy follow either theoretical or experimental results. Moroever, for higher temperatures of the thermal treatments a change in the slope of the ln (D) x 1/T diagram was observed. This anomalous behavior was associated with a secondary recrystallization as a consequence of the intermediary thermomechanical treatments. On the morphological view point, the secondary recrystallization was characterized to produce an anormal grain size with many boundary faces. Important conclusions about grain growth mechanisms were obtained. After these results, a selection of some of the elements will be made to increase the activation energy (EA) in order to stabilize the grain size.
Keywords: Grain growth ; Kinetic of growth ; Activation energy ; Secondary Recrystallization. Cinética de crescimento
COB1012 FENOMENOLOGIA DO EFEITO MEMÓRIA DE FORMA NAS LIGAS bb-CuZnSn / FENOMENOLOGY ON b-CuZnSn SHAPE MEMORY ALLOYS
Cezar Henrique Gonzalez, Claudeir Silva de Oliveira & Ney Freitas de Quadros
Departamento de Engenharia Mecânica, Área de Materiais - CTG - UFPE - Recife - Pernambuco - Brasil
Avenida Acadêmico Hélio Ramos, s/n - CDU - CEP 50 740-050 - Fone: (081) 271 8230 - Fax: (081) 271 8232
The shape memory effect on a copper based ternary alloy with 32.9wt.% and 4.0wt%Sn (copper balance) was obtained on a induction furnace and submitted to thermal treatments to retain the b-phase. The microstructural caractherization of parent and martensitic phases was done by optical microscopy and the cristalline structure by means of X-rays diffraction. The phase transformation temperatures were determined by resistivity. The influence of thermal cycling and of grain diameter were analysed in relation to these characteristical temperatures.
Keywords: Efeito Memória de Forma, Elasticidade Enantiomorfa, Transformações de Fase, Metalurgia Física / Shape
Memory Effect, Enatiomorphous Elasticity, Phase Transformations, Physical Metallurgy.
COB1013 ESTUDO DAS LIGAS bb-CuSn COM EFEITO MEMÓRIA DE FORMA / ON b-CuSn SHAPE MEMORY ALLOY
Cezar Henrique Gonzalez, Claudeir Silva de Oliveira & Ney Freitas de Quadros
Departamento de Engenharia Mecânica, Área de Materiais - CTG - UFPE - Recife - Pernambuco - Brasil
Avenida Acadêmico Hélio Ramos, s/n - CDU - CEP 50740 - 050 - Fone: (081)271 8230 - Fax: (081)271 8232
Certain copper based alloys are very susceptibles to enantiomorphous phase transformations (nucleation and growth with a well determined habit plane). The great majority of these alloys exibits the typical behavior of shape memory effect alloys and, in particular, the enantiomorphous elesticity (rubber-like), having a good potencial to industrial applications. The physical properties and microstructural characterization have been done by optical microscopy and x-rays diffraction analysis and measurements of resistivity. Hardness Vickers tests have been done to clarify the effects of aging at room and 100°C temperatures.
Keywords: Ligas com Efeito Memória de Forma, Elasticidade Enantiomorfa, Transformações de Fases, Martensita / Shape Memory Effect Alloys, Enantiomorphous Elasticity, Displacive Phase Transformations, Martensite.
COB1014 ESTUDO COMPARATIVO DAS LIGAS COM EFEITO MEMÓRIA DE FORMA bb-CuZnAl e bb-CuZnSn / ON b-CuZnAl e b-CuZnSn SHAPE MEMORY EFFECTS ALLOYS: COMPARISION STUDY
Claudeir Silva de Oliveira, Cezar Henrique Gonzalez & Ney Freitas de Quadros
Departamento de Engenharia mecânica, Área de Materiais - CTG - UFPE - Recife - Pernambuco - Brasil
Avenida Acadêmico Hélio Ramos, s/n - CDU - CEP 50740 - 050 - Fone: (081) 271 8230 - Fax: (081) 271 8232
Two ternary copper based alloys with nominal compositions (in weight %) of 32.9%Zn-4% Sn and 7.0%Zn-17.7%Al (balance Cu) with shape memory effect where characterized in relation to yours microstructural and physical properties. These alloys presented transformations temperatures that are function of composition. The alloys were done on a induction furnace using quartz crucibles. The little ingots were submitted to thermal treatments of homogenization, "betatization'' and solubilization. The microstructures of each treatment were analyzed. The material was hot milled in shapes of plates and quadratic section wires and presented the two-way shape memory effect. The microstructures of the EMF alloys were were studied by means of optical metallography and R-rays diffraction. The phase transformations temperatures were measured
by resistivity. Thermal cycling were discussed.
Keywords: Efeito Memória de Forma, Transformações de Fase, Ligas a Base de Cobre e Transformações Martensíticas /
Shape Memory Effect, Phase Transformations, Copper Based Alloys, Martensite Transformations.
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