Estudo da liga experimental Ti25Ta25Nb3Sn após deformação plástica severa (ECAP)
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Data
2020-03-20
Autores
Bortolini Junior, Celso [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Dentre os materiais utilizados em aplicações biomédicas, o titânio e suas ligas apresentaram destaque devido a suas excelentes propriedades de volume, como por exemplo, resistência mecânica. No entanto, essas propriedades estão diretamente ligadas à microestrutura, que estão diretamente relacionadas com o seu processamento. O objetivo deste trabalho foi avaliar a influência da deformação plástica severa por Equal Channel Angular Presssing (ECAP) na microestrutura e propriedades mecânicas da liga experimental Ti25Ta25Nb3Sn. Os lingotes da liga Ti25Ta25Nb3Sn foram processados em forno de fusão a arco voltaico com atmosfera controlada e submetidos a tratamento térmico de homogeneização para posterior forjamento a frio. Para o processamento por ECAP os lingotes foram previamente tratados por solubilização. Uma matriz com canal de 90º foi utilizada no processamento por ECAP, seguindo a rota Bc, processando o material com 2 e 4 passes. A morfologia, composição e estrutura foram investigadas usando microscopia eletrônica de varredura, microscopia eletrônica de transmissão e análise por EBSD. As análises de microscopia e EBSD mostraram uma estrutura com uma mistura de grãos refinados e grãos grosseiros após 2 passes e uma homogeneidade maior de grãos refinados após 4 passes. A difração de Raios X indicou a formação da fase α'' e β após 2 passes do processamento por ECAP e após 4 passes apenas a fase β estava presente na estrutura.
Titanium and its alloys have been widely used in biomedical applications due to its bulk properties, such as mechanical strength. However, these properties are very sensitive to the microstructure which depend on the processing. The purpose of this study was to evaluate the microstructure and the evolution of the mechanical properties of the Ti25Ta25Nb3Sn experimental alloy after ECAP processing. Ingots of the Ti25Ta25Nb3Sn alloy were obtained in arc melting furnace. Alloys were treated at 950° C for 24 hours for chemical homogenization in vacuum tubular furnace and cold worked by swaging into rods with 10 mm in diameter. Samples where then solution treated at 900° C for 2 hours and water quenched. Samples with 40mm in length were cut for ECAP processing. A die with a 90º channel was used for ECAP processing, following the Bc route, with 2 and 4 passes. After 2 passes samples were cut from the parallel and perpendicular directions to the ECAP and after 4 passes samples were cut only from the perpendicular direction to the ECAP, using discs with 3 mm in thickness for analysis. The morphology, composition and structure were investigated using scanning electron microscopy, transmission electron microscopy and EBSD analysis. The microscopy and EBSD analysis shows a microstructure consisting of a mix of refined and coarse grains after 2 passes and a homogeneous and refined structure after 4 passes. The X-Rays diffraction analysis indicated the formation of α'' and β phases after 2 ECAP passes and after 4 passes only the β phase was observed
Titanium and its alloys have been widely used in biomedical applications due to its bulk properties, such as mechanical strength. However, these properties are very sensitive to the microstructure which depend on the processing. The purpose of this study was to evaluate the microstructure and the evolution of the mechanical properties of the Ti25Ta25Nb3Sn experimental alloy after ECAP processing. Ingots of the Ti25Ta25Nb3Sn alloy were obtained in arc melting furnace. Alloys were treated at 950° C for 24 hours for chemical homogenization in vacuum tubular furnace and cold worked by swaging into rods with 10 mm in diameter. Samples where then solution treated at 900° C for 2 hours and water quenched. Samples with 40mm in length were cut for ECAP processing. A die with a 90º channel was used for ECAP processing, following the Bc route, with 2 and 4 passes. After 2 passes samples were cut from the parallel and perpendicular directions to the ECAP and after 4 passes samples were cut only from the perpendicular direction to the ECAP, using discs with 3 mm in thickness for analysis. The morphology, composition and structure were investigated using scanning electron microscopy, transmission electron microscopy and EBSD analysis. The microscopy and EBSD analysis shows a microstructure consisting of a mix of refined and coarse grains after 2 passes and a homogeneous and refined structure after 4 passes. The X-Rays diffraction analysis indicated the formation of α'' and β phases after 2 ECAP passes and after 4 passes only the β phase was observed
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Palavras-chave
Ligas de Titânio, Propriedades mecânicas, Caracterização microestrutural, ECAP, Titanium alloys, Microstructural characterization, Mechanical properties., Ligas - Propriedades mecânicas, Materiais biomédicos