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Title: Fatigue and fracture of the ultrahigh strength steel AerMet 100
Author: Hill, Paul Owen
ISNI:       0000 0004 2741 3550
Awarding Body: University of Birmingham
Current Institution: University of Birmingham
Date of Award: 2012
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This thesis considers the fatigue and fracture behaviour of ultra-high strength steel, AerMet 100. Two variants of AerMet 100 were tested, which had different desulphurisation and deoxidation methods. The first was desulphurised and deoxidised using mischmetal, designated MMAerMet 100. The second was desulphurised using calcium and deoxidised using titanium, designated Ca-AerMet 100. Axial fatigue testing below the 0.2% proof stress was carried out between stress ranges of 900-1700 MPa. Fractography revealed that the fatigue initiation sites could be traced to non-metallic inclusions. Samples tested in the longitudinal orientation had better fatigue lives compared to samples tested in the transverse orientation. A stress intensity factor range at the cracked inclusion at the point of initial fatigue crack growth showed a good correlation with fatigue life. Ca-AerMet 100 consistently had a better fatigue life compared to MM-AerMet 100. Fracture toughness testing showed that both variants of AerMet 100 had similar fracture toughness values and fractured by micro-void coalescence. Fractography revealed that 90% of the fracture surface was made from voids formed from secondary particles with approximate diameters of 90 nm. The work suggests that changing the desulphurisation and deoxidation method for AerMet 100 has not significantly affected the fracture toughness.
Supervisor: Not available Sponsor: Rolls Royce plc
Qualification Name: Thesis (D.Eng.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TN Mining engineering. Metallurgy