Vacancy-Induced Solute Clustering and Precipitation in Lightweight Alloys

Understanding the thermodynamic role of excess vacancies in controlling solute clustering and precipitation behavior in Mg and Al alloys.

This NSF-funded project investigates the role of excess vacancies in driving solute clustering and precipitation in magnesium and aluminum alloys. These insights support the development of high-performance, lightweight materials for structural and biomedical applications.

Conducted in collaboration with
Prof. Michael Falk (JHU), Dr. Arun Devaraj (PNNL), Dr. Marc H Weber (WSU), and Dr. Mark McLean (NIST), this project integrates advanced characterization with defect thermodynamics.

Research Objectives

  • Quantify vacancy concentrations generated by processing.
  • Examine how vacancies influence solute clustering and precipitation.
  • Understand fundamental thermodynamics of vacancy–solute interactions.

Methodology

Vacancy Manipulation:

  • Controlled quenching and deformation introduce tailored vacancy concentrations.

Characterization Suite:

  • Positron Annihilation Spectroscopy (PAS) – quantifies vacancy concentration.
  • Atom Probe Tomography (APT) – 3D mapping of solute cluster structures.
  • XRD & TEM – validate phase formation and crystallographic structure.

Systems Under Study:

  • Mg Alloys: Mg–Al, Mg–Zn, Mg–Y
  • Al Alloys: Al–Mg, Al–Ag, Al–Cu

Mechanistic Insights:

  • Simulations and theory help correlate experimental data with clustering energetics.
Schematic overview of vacancy introduction and characterization techniques across multiple alloy systems.

APT Tomography

Atom Probe Tomography reveals 3D solute clustering in vacancy-rich zones of Mg-Zn alloy.

Outcomes and Impact

  • Enables defect-level control over strengthening behavior.
  • Reveals how vacancies assist or hinder early-stage clustering and precipitation.
  • Supports the design of durable, bio-compatible materials with tunable nanoscale properties.

Keywords: vacancies, solute clustering, precipitation, APT, PAS, thermodynamics, magnesium alloys, aluminum alloys, NSF, advanced characterization