Solute Effects on Indentation Modulus and Hardness in Multi-Alloy Systems

Project Goal:

Quantify how varying solute concentrations (Ti, Ni, Cr, and Ta) influence microscale mechanical response using controlled heat treatment and nanoindentation across a total of 11 alloy samples, with particular emphasis on titanium as a solute in Nb–Ti alloys through comparison of two Nb-rich compositions (95% Nb–5% Ti and 90% Nb–10% Ti).

Role & Responsibilities:

Prepared and mounted alloy samples for testing (sectioning, resin mounting, polishing workflow).
Set up and executed nanoindentation experiments, including identifying defect-free regions and running indentation grids.
Analyzed depth-dependent trends in hardness and reduced modulus and connected observations to measurement artifacts at shallow depths.

Research Context:

The mechanical performance of structural alloys is strongly influenced by solute chemistry and atomic-scale interactions within the crystal lattice. Variations in alloying elements, such as Ti, Ni, Cr, and Ta, alter the elastic and plastic deformation behavior, which directly impacts performance in aerospace and high-performance applications. However, isolating the effects of individual solutes is challenging due to the microstructural complexity and interactions with defects. This research addresses these challenges by using controlled heat treatment and nanoindentation to quantify solute-driven changes in indentation modulus and hardness across multi-alloy systems.

a) Ti-Ta and b) Ni-Ti-Ta samples mounted and cured in resin. They are labeled with the area where the nanoindentation grid was placed.

Technical Skills: Non-technical Skills

Nanoindentation Experimental planning
Alloy sample preparation Project coordination
Heat treatment Data interpretation
Mechanical property analysis Technical documentation
Data analysis Experimental planning

Results & Future Plan

Observed trend: hardness and modulus stabilize toward a representative “bulk” value as depth increases; early-depth values can be inflated by contact-area uncertainty and tip/surface effects.
Next steps: use EDX to distinguish compositions in mixed-color mounts, complete CSM/SRJ testing on Nb–Ti samples, and process results in Origin to generate averaged property-vs-depth plots.
Planned correction: use AFM to correct hardness by measuring the true contact area when pile-up affects the apparent area from nanoindentation.

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