Laser Precision Manufacturing: Microstructure, Surface, and Property Control
Date Issued
May 2026
Author(s)
Fieser, David James
The University of Tennessee
Advisor(s)
Anming Hu
Additional Advisor(s)
Zhili Feng
Seungha Shin
Peter Liaw
Abstract
Laser precision manufacturing enables targeted control of microstructure, surface state, and functional properties by coupling laser energy delivery with environmental and spatial boundary conditions. This dissertation investigates that coupling across three length scales: nanoscale synthesis, mesoscale powder bed fusion, and microscale surface processing. At the nanoscale, femtosecond laser ablation in liquids is used to synthesize high-purity CuCoMn1.75NiFe0.25 high-entropy alloy nanoparticles. A scalable ablation platform with continuous filtration is demonstrated, and the resulting nanoparticles retain a single-phase face-centered cubic structure with promising electrocatalytic activity for oxygen reduction, oxygen evolution, and hydrogen evolution reactions. Extending this work, a systematic comparison of ablation in ethanol and liquid nitrogen reveals that solvent choice governs particle size distribution, crystallographic defect density, elemental homogeneity, and surface oxide chemistry. Liquid nitrogen quenching preserves compositional fidelity and produces structurally continuous nanoparticles, whereas ethanol ablation yields nanocrystalline aggregates with higher mixing enthalpy and reduced thermodynamic stability. Cooling simulations and thermodynamic descriptor analysis connect these differences to solvent-dependent heat extraction rates and to the balance between enthalpy and entropy contributions. At the mesoscale, laser powder bed fusion of a near-eutectic Al–Ce–Ni–Mn–Zr alloy designed for elevated-temperature service is optimized through a 60-build design of experiments that maps laser power, scan speed, and hatch spacing to porosity and hardness responses. A Rosenthal-based cooling rate metric captures more than half the variation in both responses, yielding a defined processing window (350–370 W, 1400–1800 mm/s, 0.14–0.18 mm hatch) that produces porosity below 0.01 vol% and as-built hardness up to 160 HV at cooling rates of 3.0–3.6 × 106 K/s. At the microscale, a hybrid two temperature model is developed for multi-pulse femtosecond laser processing of tungsten. The method solves the full coupled electron–lattice system during each pulse on a fine grid and hands off the equilibrated profile to Crank–Nicolson diffusion on a coarser grid through the inter-pulse gap, running roughly two orders of magnitude faster than monolithic integration. Validation against a scanning experiment at 40 MHz shows that the predicted melt zone diameter of 25.0 μm matches the measured central zone exactly, with no fitted parameters. Across all scales, the results show that jointly controlling energy delivery, processing environment, and thermal boundary conditions provides repeatable pathways from process inputs to microstructure to properties.
Disciplines
Degree
Doctor of Philosophy
Major
Mechanical Engineering
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