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Title: Study of phase decomposition and coarsening of γ′ precipitates in Ni-12 at.% Ti alloy

The early stages of phase decomposition, morphological evolution of precipitates, coarsening kinetics of γ′ precipitates and micro-hardness in Ni-12 at.% Ti alloy are studied by transmission electron microscopy (TEM) and Vickers hardness tests (VHN). Disk-shaped specimens are solution treated at 1473 K (1200 °C) and aged at 823, 923 and 1023 K (550, 650 and 750 °C) during several periods of time. TEM results show that a conditional spinodal of order occurs at the beginning of the phase decomposition and exhibit the following decomposition sequence and morphological evolution of precipitates: α{sub sss} → γ″ irregular–cuboidal + γ{sub s} → γ′ cuboidal–parallelepiped + γ → η plates + γ. In general during the coarsening of γ′ precipitates, the experimental coarsening kinetics do not fit well to the LSW or TIDC (n = 2.281) theoretical models, however the activation energies determined using the TIDC and LSW theories (262.846 and 283.6075 kJ mol{sup −1}, respectively) are consistent with previously reported values. The highest hardness obtained at 823, 923 and 1023 K (550, 650 and 750 °C) is associated with the presence of γ′ precipitates. - Highlights: • It was studied the conditional spinodal during early stages of phase decomposition. • It was obtainedmore » decomposition sequence and morphological evolution of precipitates. • It was experimentally evaluated the coarsening kinetics of γ′ precipitates. • The maximum hardness is associated with the γ′ precipitates.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [1] ;  [5] ;  [4] ;  [1]
  1. Universidad Autónoma de San Luis Potosí, Instituto de Metalurgia, Sierra leona 550, Col. Lomas 2 sección, 78210 S.L.P. (Mexico)
  2. Instituto Politécnico Nacional, ESIME-AZC, Av. de las Granjas 682, col. Sta. Catarina, 02550 D.F. (Mexico)
  3. Instituto Potosino de Investigación Científica y Tecnológica, División de Materiales Avanzados, camino a la Presa San José 2055, Col Lomas 4 sección, 78216 S.L.P. (Mexico)
  4. Instituto Politécnico Nacional, ESIQIE-DIM, 118-556, D.F. (Mexico)
  5. Centro de Investigación de Materiales Avanzados (CIMAV), Laboratorio Nacional de Nanotecnología, Miguel de Cervantes 120, 31109 Chihuahua (Mexico)
Publication Date:
OSTI Identifier:
22285075
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Characterization; Journal Volume: 83; Other Information: Copyright (c) 2013 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ACTIVATION ENERGY; DECOMPOSITION; HARDNESS; HEAT RESISTING ALLOYS; NICKEL; PRECIPITATION; TRANSMISSION ELECTRON MICROSCOPY; VICKERS HARDNESS