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Title: The measurement of toughness in ferritic steels using miniature test techniques
Author: Norris, S. D.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1995
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Typical alloy steels such as 21/4Cr1Mo steel used in critical components in high temperatures and pressure service applications, are susceptible to time dependent mechanical and fracture property degradation. Measurement of changes to these properties by conventional standard test techniques has severe size and cost limitations. For these reasons the use of miniaturised testing techniques is a favourable alternative for producing critical mechanical and fracture data. The present study used a miniaturised disk bend test technique to evaluate mechanical and fracture properties for a range of alloy steels including, normalised and tempered, furnace aged and ex-service 21/4Cr1Mo steel for comparison to standard test techniques. The Standard techniques were tensile tests, Charpy tests and compact tension tests. Empirical correlations were found between the disk test and tensile, Charpy and compact tension tests respectively. The majority of the testing and analysis used the 21/4Cr1Mo steel to study the variation of disk bend tests with temperature. Changes were discussed with reference to the competitive processes of deformation and fracture. The temperature dependence of the yield and flow stress, and the temperature independence of the material fracture stress were found to be the controlling factors in the transition from ductile to brittle fracture with temperature. Ductile and brittle fracture are controlled by microstructural features of non-metallic inclusions and carbide particles respectively. It was found from studies of ductile cracking in disk tests at one temperature, that the distribution of non-metallic inclusions could be linked to the variation of data produced. From studies of furnace aged material the effect of carbide coarsening was found to influence the brittle fracture of the material during disk tests.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available