Structural Study of Novel Nanocrystalline fcc Ti-Ta-Sn Alloy
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and titanium-based alloys are widely being used in engineering applications due to their high strength to weight ratio,[1] excellent corrosion resistance[2] and negligible biological impact on human body.[3] Pure Ti has an allotropy change, it exhibits a hexagonal closely packed (hcp) crystalline structure below of 882 C ± 2 C and over that temperature it has a body-centered cubic (bcc) crystalline structure. On the other hand, the presence of metastable fcc phase in
C. AGUILAR and E. PIO are with the Departamento de Ingenierı´ a Metalu´rgica y Materiales, Universidad Te´cnica Federico Santa Marı´ a, Av. Espaa 1680, Valparaı´ so, Chile. Contact e-mail: claudio.aguilar@ usm.cl A. MEDINA and L. BEJAR are with the Instituto de Investigaciones en Metalurgia y Materiales, Universidad Michoacana de San Nicola´s de Hidalgo, Gral. Francisco J. Mugica S/N, Ciudad Universitaria, 58030 Morelia, Mexico. R.V. MANGALARAJA and C. SALVO are with the Laboratorio de Cera´micos Avanzados y Nanotecnologia, Departamento de Ingenierı´ a de Materiales, Universidad de Concepcio´n, Concepcio´n, Chile. I. ALFONSO is with the Instituto de Investigaciones en Materiales, Universidad Nacional Auto´noma de Me´xico, Campus Morelia UNAM, Antigua Carretera a Pa´tzcuaro No. 8701, Col. Ex-Hacienda de San Jose´ de la Huerta, C.P. 58190, Morelia, Michoaca´n. Mexico. D. GUZMA´n is with the Departamento de Metalurgia, Universidad de Atacama, Av. Copayapu 485, Copiapo´, Chile. Manuscript submitted January 16, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS A
pure Ti[4,5] and Ti-based alloys synthesized by several processing methods have been reported.[6,7] Xiong et al.[8] studied the effect of size and temperature on the formation of fcc Ti phase and determined that Gibbs-free energy values reach minimum when the particle size is in nanocrystalline range. According to the literature, the main conditions required for the formation of the fcc Ti phase are: severe plastic deformation and/or nanocrystalline sizes. Yu et al.[4] found that fcc phase is stable under mechanical deformation and exhibited similar mechanical deformation behavior as the parent hcp phase. Chang et al.[9] reported that the phase transformation from hcp to fcc dominates the plastic deformation for the sizes smaller than 20 nm at the strain rate of 108 to 109 s1. Zhang and Ying[10] reported the hcp to fcc phase transformation during high-energy ball milling of Al-25 at. pct Ti and Ti-25 at. pct Al powders. Wu et al.[11] observed that fcc nucleation is accomplished via pure-shuffle mechanism with a minimum stable thickness of three atomic layers and the growth via shear-shuffle mechanisms through gliding two-layer disconnections. To the best of our knowledge, the detailed microstructural X-ray diffraction (XRD) characterization of fcc Ti phase has been rarely discussed and reported in the literature. The reports focused basically on pure Ti and binary Ti-based alloys. It is well known that the X-ray diffraction profile analysis has become a powerful tool and a detailed microstructural analysis
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