Laser-based direct energy deposition of compositionally graded titanium alloys: Microstructural evolution, hardness, and tensile properties
Bibliographic record
Abstract
Laser-based direct energy deposition (DED) technology allows researchers to alter feeding materials while fabricating products and offering opportunities for producing compositionally graded materials such as graded alloys for structural applications. Many graded alloys suffer from their poor tensile properties due to asperities formed at the interface of two materials, arising from microstructural mismatches and varying thermal properties. Towards the load-bearing applications of lightweight dissimilar titanium alloys, we employ the DED method to fabricate a compositionally graded material consisting of the Ti-6Al-4V (TC4) alloy and Ti-6.5Al-3.5Mo-1.5Zr-0.3Si (TC11) alloy. We investigate the effects of heterogeneous microstructure and compositions on the hardness and tensile properties of the graded TC11-TC4 alloy, as well as heat treatment effects, to unveil their microstructure evolution and deformation mechanisms. The smooth change of chemical compositions across the graded TC11-TC4 alloy interface leads to a smooth change of interfacial hardness from ∼320 HV0.3 on the TC4 side to ∼380 HV0.3 on the TC11 side. The as-deposited and heat-treated specimens show comparable yield strength (806–860 MPa), ultimate tensile strength (921–937 MPa), and ductility (7.8–8.6 %) despite different microstructures. We demonstrate a correlation between the microstructural features and micro-deformation mechanisms in each region of the graded Ti-alloy, showing that the graded interfacial region resists plastic strain localization. The micro- and macro-mechanical properties of the graded alloy are associated with the distribution, size, morphology, and orientation of the α and β phases. • Graded TC11-TC4 titanium alloy manufactured using direct energy deposition method. • As-deposited and heat-treated alloys showed superior performance at the interface. • Coherent metallurgical bonding led to a strong graded interface. • Graded chemical composition controlled the phase size and distribution. • Local deformation behavior of phases affected the global mechanical properties.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".