Insights into Grain Structures and Their Reactivity on Grade-2 Ti Alloy Surfaces by Scanning Electrochemical Microscopy
Bibliographic record
Abstract
The corrosion resistance of titanium and its alloys is a desirable property for many applications in materials science. In this report, the properties of the passive oxide film (TiO 2 ) were examined by scanning electrochemical microscopy (SECM). A homemade closed-loop scanning electrochemical microscope was used to study these properties at the micrometer scale using ferrocenemethanol (Fc) as the redox mediator. The experimental results showed that the passive properties of a well-polished ASTM Grade-2 titanium (Ti-2) sample differed from region to region as indicated by the different current responses of the ultramicroelectrode (UME) on the SECM images. Selected spots with high feedback tip current were examined more closely by additional scanning. It was concluded that active spots with high positive feedback current were indicative of reactive structures located along crystalline grain boundaries, especially at the triple points. This observation is confirmed by comparing SECM results with optical micrographs reported in the literature. Previous metallographic investigations show these are the sites where the impurity iron content of the alloy congregates. This is confirmed by our experiments on scanning electron microscopy and energy dispersive X-ray analysis. For the first time, grain microstructure maps have been constructed on the SECM images, based on the above active sites. The properties of TiO 2 films on Ti-2 were also assessed at various applied potentials. The reactivity of the oxide-covered Ti-2 surface increased and more active spots appeared when the Ti-2 bias potential was made more negative. This was attributed to oxide reduction (Ti(IV) to Ti(III)) and the onset of the absorption of hydrogen. The potential at which this change occurred varied at different sites on the scale of the grain structure (20−100 μm). These results demonstrate that SECM is a noninvasive analytical methodology that can provide insights into the structures and reactivities of Ti-2.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.000 | 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 teacher head, 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".