Creep failure of aluminium alloys at high temperatures

McLure, Alexander (1972) Creep failure of aluminium alloys at high temperatures. PhD thesis, University of Glasgow.

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Abstract

The majority of polycrystalline metals and alloys, when subjected to certain conditions of stress at temperatures > 0.5 Tm (Tm - melting temperature), display an intercrystalline mode of failure. In general, this type of fracture occurs under creep conditions when the applied stress system produces low strain rates and long rupture lives. Low ductility, as measured by elongation and reduction of area at fracture, characterises the failure. Research has established that the failure is initiated by the nucleation and subsequent growth of sub-microscopic fissures in the grain boundaries. Although it is to be expected that the development of discontinuities in the grain boundaries should adversely affect the creep properties of a metal or alloy, it is not clear how the effect might vary with temperature and/or stress system. The existence of discontinuities in a stressed material produces local stress concentrations around those discontinuities. However, since ease of plastic flow varies with both temperature and stress system, the effect of the discontinuities on creep properties can also be expected to vary with temperature and stress system. In addition, the question arises as to whether the appearance of discontinuities in the grain boundaries necessarily constitutes failure. The main objective of this research was, therefore, to determine the effects that intergranular discontinuities have on the creep Properties of a metal or alloy under different conditions of stress and temperature and under different stress systems. Commercially pure aluminium (99.0 + pet) was chosen for the study. Specimens of the material were strained at constant rate and a temperature of 500

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: P Hancock
Keywords: Materials science, Thermodynamics
Date of Award: 1972
Depositing User: Enlighten Team
Unique ID: glathesis:1972-72888
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 11 Jun 2019 11:06
Last Modified: 11 Jun 2019 11:06
URI: http://theses.gla.ac.uk/id/eprint/72888

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