Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636787
Title: The creep, grain boundary sliding and fracture of copper alloys
Author: Elliott, I. C.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1980
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Abstract:
The present research programme has been devised to study the creep deformation and fracture behaviour of Cu-Zn alloys. A review of literature has been made in order to assess the mechanisms of nucleation and growth of intergranular cavities and their subsequent interlinkage to form cracks which result in fracture. The creep behaviour of single phase alpha-brass was characterised over a range of applied stresses at 686, K (ti 0.5 T ) and the fracture mechanism studied by metallographic and fractographic techniques. Although metallographic evidence indicated that the process of intergranular creep failure was similar at high and low stresses, fractography revealed that the appearance of the fracture surfaces was distinctly different. The apparently different modes of void formation observed was rationalised in terms of a model for cavity growth based on the movement of lattice dislocations in the plane of the grain boundary. Similar studies were carried out for two phase alpha-beta brass. This alloy was found to be substantially less creep resistant than alpha-brass due to the ease of deformation of the beta phase. Creep fracture occurred due to the development of voids in the beta phase regions which grew and necked together by plastic flow to form large tears. The tears were found to be both interphase and transgranular in nature, depending on the original void distribution, but the failure was essentially transgranular. As the beta phase was not continuous at the testing temperature (686 K) tears in beta phase regions interlinked through the failure of intervening a-a-boundaries, predominantly by wedge cracking due to the massively deforming beta phase allowing large relative rotations of adjacent alpha grains. The creep fracture behaviour of the two alloys studied was therefore found to be fundamentally different, the present investigation demonstrating that failure of alpha-beta brasses can take place in an essentially ductile transgranular manner under conditions which result in intergranular fracture of alpha-brasses.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.636787  DOI: Not available
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