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Achieving fine beta grain structure in a metastable beta titanium alloy through multiple forging-annealing cycles
journal contributionposted on 2016-07-01, 00:00 authored by A Zafari, Y Ding, J Cui, K Xia
A coarse-grained (order of 1 mm) Ti-5553 metastable beta alloy was subjected to multiple passes of low-temperature forging and multiple forging plus annealing cycles, respectively. In the forging only processing, strain was concentrated in the shear bands formed and accumulated with each forging pass, resulting in a heterogeneous microstructure and eventual cracking along the shear bands. In contrast, the introduction of a short beta annealing after each forging step led to fine recrystallized grains (50 to 100 µm) formed in the shear bands, and a uniformly refined beta grain structure after four cycles. This is attributed to the strengthening effect of the fine grains, causing redistribution of most severe strains to the coarse grain region in the subsequent forging, consistent with the simulated results by finite element analysis. The analyses of the microstructures and simulated strain distributions revealed that the critical strain for recrystallization is between 0.2 and 0.5 and the strain to fracture to be ~0.8 to 0.9. The fine-grained (50 to 100 µm) beta alloy, however, fractured at a much smaller strain of <0.4 during the next forging step, owing to the formation of stress-induced martensitic α″ which is more prevalent in fine grains than in coarse ones.
JournalMetallurgical and materials transactions A
Pagination3633 - 3648
LocationNew York, N.Y.
Publication classificationC Journal article; C1.1 Refereed article in a scholarly journal
Copyright notice2016, The Minerals, Metals & Materials Society and ASM International
Science & TechnologyTechnologyMaterials Science, MultidisciplinaryMetallurgy & Metallurgical EngineeringMaterials ScienceSEVERE PLASTIC-DEFORMATIONHIGH-PRESSURE TORSIONINDUCED MARTENSITIC-TRANSFORMATIONMECHANICAL-PROPERTIESOMEGA PHASEDYNAMIC RECRYSTALLIZATIONBOUNDARY MOTIONSELF-DIFFUSIONGROWTHSIZEMechanical Engineering