Dissertation
Dissertation > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metal corrosion protection,metal surface treatment > Corrosion control and protection > Corrosion testing and equipment

Investigation on Corrosion Fatigue Behavior of TA15 Alloy in 3.5%NaCl Salt Spray

Author WuDaZuo
Tutor YeZuoYi
School Zhejiang University
Course Chemical Process Equipment
Keywords TA15 alloy Corrosion fatigue Mechanical behavior Mesostructure Fracture
CLC TG174.3
Type Master's thesis
Year 2011
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TA15 alloy Al equivalent of a high the near α strength titanium alloy with good mechanical properties and excellent forging, heat treatment and welding process performance, and has a broad application prospects in the aircraft structure. The atmosphere contains a lot of salt spray in coastal areas, in-service aircraft structural parts inevitably suffer from salt spray corrosion damage, therefore, the study has important practical significance TA15 alloy corrosion fatigue behavior in the salt spray environment. This paper studies a the TA15 alloy in 3.5% NaCl salt spray environment on the mechanical behavior of the corrosion fatigue stress ratio (R = -1, R = 0.06 and R = 0.5). The test results show that alloy corrosion fatigue cyclic deformation behavior role stress ratio related: R = -1 under the conditions, the material is rendered as a cyclic softening characteristics; R = 0.06 under the conditions, the material exhibits a stable circulation phenomenon; while in the R = 0.5 under the conditions, the material exhibits cyclic hardening characteristics. Statistical analysis of experimental data given under different stress ratio SN the the curve containing different survival pSN curve. Different stress than under corrosion fatigue limit compared based on: salt spray environment, mean stress on the fatigue life of alloy corrosion meets Soderberg relationship. Also establish describe the mean stress Sm stress amplitude Sa and corrosion fatigue life N relations among Sm-Sa-N surface equation containing different survival p-Sm-Sa-N surface equation. Depth - sensitive indentation technique papers corrosion fatigue before and after TA15 alloy metallographic two types of organizations (axis α phase and transformed β phase) structure micromechanics characteristics test. The test results show that the the original sample medium axis α organizations microhardness greater than β transformation Organization. Compared before and after corrosion fatigue test data derived: the equiaxed α organizations strength higher than β change in organizations, the ability to have a strong resistance to crack initiation, The Corrosion Fatigue meso organizational structure visible damage; transformed β organizations toughness to be higher than the newborn axis α organizations, manifested as a strong resistance to crack propagation, corrosion fatigue meso smaller organizational structure damage. SEM results show that corrosion fatigue fracture: salt spray environment, the alloy corrosion fatigue fracture crack originated in the surface of the sample, and with increasing stress ratio, multi-the Fatigue source characteristics become significant. With the increase of the stress ratio, the cleavage characteristics of the corrosion fatigue crack source region will become more apparent, and the extended area fatigue stripes become more dense.

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