Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-12-01T23:25:13Z No. of bitstreams: 1 ThiagoSouzaViana_DISSERT.pdf: 4828616 bytes, checksum: ee06ed8ff3676ebb8c30b440a888b38d (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-12-05T20:32:59Z (GMT) No. of bitstreams: 1 ThiagoSouzaViana_DISSERT.pdf: 4828616 bytes, checksum: ee06ed8ff3676ebb8c30b440a888b38d (MD5) / Made available in DSpace on 2017-12-05T20:32:59Z (GMT). No. of bitstreams: 1 ThiagoSouzaViana_DISSERT.pdf: 4828616 bytes, checksum: ee06ed8ff3676ebb8c30b440a888b38d (MD5) Previous issue date: 2017-06-30 / No presente trabalho, estudou-se a influ?ncia de tratamentos t?rmicos nas transforma??es microestruturais de uma liga NiTi com mem?ria de forma de composi??o qu?mica aproximadamente equiat?mica. Um fio de NiTi com 2,5 mm de di?metro, recebido no estado encruado, foi submetido a tratamentos t?rmicos de recozimento em temperaturas de 450 ?C e 500 ?C para observa??o das varia??es microestruturais. As microestruturas predominantes antes e ap?s o recozimento foram observadas, registrando-se um aumento na granulometria da martensita tanto com a temperatura como com a dura??o do tratamento t?rmico entre 30? e 3hs. Foram determinadas as temperaturas de transforma??o, (As, Af, Ms, Mf) de cada amostra, e as altera??es nas temperaturas de transforma??o entre o material no estado encruado e ap?s recozimento. Medidas de microdureza n?o revelaram influ?ncia significativa de tratamentos t?rmicos de recozimento e tampouco de resfriamentos a temperaturas subzero. / In the present work, the influence of heat treatments on the microstructural transformations of an approximately equiatomic NiTi memory form alloy was investigated. A NiTi wire with 2.5 mm in diameter, received in the work hardened state, was submitted to annealing heat treatments at 450 ?C and 500 ?C in order to verify the calorimetric and microstructural changes. The microstructure in the work hardened condition and after the annealing heat treatments was analyzed, which showed a coarsening of the martensite plates for higher temperatures and longer heat treatment times. The determination of the transition temperatures (As, Af, Ms, Mf) and the change in the transformation temperatures between the as received worked hardened and annealed material, were determined. Microhardness measurements did not reveal any significant influence of the annealing or subzero heat treatments on the mechanical behavior of the alloy.