Microstructure and tensile deformation mechanism of Ti–6Al–2Sn–4Zr–2Mo alloy fabricated by directed energy deposition process
In this study, the microstructural evolution and tensile deformation behavior of a Ti–6Al–2Sn–4Zr–2Mo (Ti6242) alloy fabricated via directed energy deposition (DED) were systematically characterized. Microstructural analysis revealed that both as-built and stress-relieved samples exhibited α+β lamel...
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| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Elsevier
2025-09-01
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| Series: | Journal of Materials Research and Technology |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2238785425019027 |
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| Summary: | In this study, the microstructural evolution and tensile deformation behavior of a Ti–6Al–2Sn–4Zr–2Mo (Ti6242) alloy fabricated via directed energy deposition (DED) were systematically characterized. Microstructural analysis revealed that both as-built and stress-relieved samples exhibited α+β lamellar structures, with no evidence of α′ martensite. Stress-relief treatment (600 °C/3 h) resulted in slight coarsening of the α-laths, with negligible changes in residual stress or phase fraction. Despite being in the as-built state, the alloy demonstrated excellent tensile properties (UTS ∼1085 MPa, elongation ∼12.1 %), comparable to those of heat-treated cast counterparts. This mechanical performance is attributed to the refined α+β lamellar structure and the absence of major defects such as porosity and strain-age cracks. Fractographic and cross-sectional analyses revealed uniformly ductile fractured surfaces and crack propagation paths traversing lamellar colonies, indicating enhanced fracture resistance. Transmission electron microscopy (TEM) performed near and away from the fracture surface allowed us to infer the sequential deformation behavior during room-temperature tensile loading. In regions adjacent to the fracture surface, tangled dislocations were homogeneously distributed within both α and β phases, suggesting uniform deformation conducive to good plasticity. At approximately 1.5 mm from the fracture surface, dislocations were aligned in parallel and accompanied by slip traces across α/β interfaces, indicating efficient slip transfer. Crystallographic analysis confirmed that slip transfer occurred from α prismatic (1‾1‾20) plane to β (1‾21) plane across an interface with a ∼150° planar angle, enabling smooth dislocation motion across the phase boundary. This favorable crystallographic alignment played a crucial role in strain accommodation and was instrumental in achieving the excellent tensile properties observed in the as-built Ti6242 alloy. |
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| ISSN: | 2238-7854 |