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Title: Comments on Steady-state creep deformation of investment cast near-gamma titanium aluminide

Abstract

In a recent article, the creep behavior of a near-gamma Ti-48Al-2Nb-2Cr (at.%) cast alloy was investigated. The results and analyses are criticized as follows: Firstly, it is difficult to measure strain rates slower than 10[sup [minus]8]s[sup [minus]1] by conducting creep tests for only' 100 hours, since this corresponds to strains below 0.0036. Secondly, the activation energies for creep at 103 and 172 MPa calculated by the authors are incorrect. At 103 MPa, the activation energy for creep is [approximately]240 kJmol[sup [minus]1] rather than 300 kJmol[sup [minus]1] (data from Fig. 2). At 172 MPa, the stress exponents are clearly different from each other at the three temperatures; hence, an activation energy for creep associated with a single deformation mechanism cannot be determined. Thirdly, the authors claim that in the region where the stress exponent, n, is equal to three, dislocation pipe diffusion is controlling a stress-assisted diffusional creep mechanism...'. This is most likely incorrect since, when a diffusional creep mechanism (Nabarro-Herring/Coble) is dominating the deformation behavior, no dislocation motion is expected; as a consequence, the dislocation density should remain constant with applied stress in the low applied stress regime. In conclusion, it is difficult to determine the creep mechanism(s) of thismore » alloy based on the data presented.« less

Authors:
 [1];  [2]
  1. Centro Nacional de Investigaciones Metalurgicas, Madrid (Spain)
  2. Univ. of California, Irvine (United States)
Publication Date:
OSTI Identifier:
6520722
Resource Type:
Journal Article
Journal Name:
Scripta Metallurgica et Materialia; (United States)
Additional Journal Information:
Journal Volume: 28:7; Journal ID: ISSN 0956-716X
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALUMINIUM ALLOYS; CREEP; CHROMIUM ALLOYS; NIOBIUM ALLOYS; TITANIUM ALLOYS; DATA ANALYSIS; DEFORMATION; STRAIN RATE; ALLOYS; MECHANICAL PROPERTIES; 360103* - Metals & Alloys- Mechanical Properties

Citation Formats

Gonzalez-Doncel, G, and Wolfenstine, J. Comments on Steady-state creep deformation of investment cast near-gamma titanium aluminide. United States: N. p., 1993. Web. doi:10.1016/0956-716X(93)90371-X.
Gonzalez-Doncel, G, & Wolfenstine, J. Comments on Steady-state creep deformation of investment cast near-gamma titanium aluminide. United States. https://doi.org/10.1016/0956-716X(93)90371-X
Gonzalez-Doncel, G, and Wolfenstine, J. 1993. "Comments on Steady-state creep deformation of investment cast near-gamma titanium aluminide". United States. https://doi.org/10.1016/0956-716X(93)90371-X.
@article{osti_6520722,
title = {Comments on Steady-state creep deformation of investment cast near-gamma titanium aluminide},
author = {Gonzalez-Doncel, G and Wolfenstine, J},
abstractNote = {In a recent article, the creep behavior of a near-gamma Ti-48Al-2Nb-2Cr (at.%) cast alloy was investigated. The results and analyses are criticized as follows: Firstly, it is difficult to measure strain rates slower than 10[sup [minus]8]s[sup [minus]1] by conducting creep tests for only' 100 hours, since this corresponds to strains below 0.0036. Secondly, the activation energies for creep at 103 and 172 MPa calculated by the authors are incorrect. At 103 MPa, the activation energy for creep is [approximately]240 kJmol[sup [minus]1] rather than 300 kJmol[sup [minus]1] (data from Fig. 2). At 172 MPa, the stress exponents are clearly different from each other at the three temperatures; hence, an activation energy for creep associated with a single deformation mechanism cannot be determined. Thirdly, the authors claim that in the region where the stress exponent, n, is equal to three, dislocation pipe diffusion is controlling a stress-assisted diffusional creep mechanism...'. This is most likely incorrect since, when a diffusional creep mechanism (Nabarro-Herring/Coble) is dominating the deformation behavior, no dislocation motion is expected; as a consequence, the dislocation density should remain constant with applied stress in the low applied stress regime. In conclusion, it is difficult to determine the creep mechanism(s) of this alloy based on the data presented.},
doi = {10.1016/0956-716X(93)90371-X},
url = {https://www.osti.gov/biblio/6520722}, journal = {Scripta Metallurgica et Materialia; (United States)},
issn = {0956-716X},
number = ,
volume = 28:7,
place = {United States},
year = {1993},
month = {4}
}