Using Spinodal Decomposition to Investigate Diffusion Enhancement and Vacancy Population

Area of Science:

• Materials Science
• Metallurgy
• Physical Chemistry

Background:

• Material strengthening is key for sustainability, but diffusion-driven precipitation is slow due to low equilibrium vacancy concentrations.
• Existing methods struggle to measure and map low vacancy concentrations (below 10⁻⁷) in alloys.

Purpose of the Study:

• To investigate diffusion enhancement and local vacancy populations in an Al-Zn system.
• To develop a method for measuring and mapping excess vacancies in alloys at sub-micrometer scales.

Main Methods:

• Utilized cryogenic processes (liquid nitrogen quenching) to preserve excess vacancies in an Al-12.5 at.% Zn alloy.
• Analyzed vacancy-mediated gradient microstructures near grain boundaries.
• Measured intermittent compositional fluctuations during ultrafast spinodal decomposition to assess diffusion and vacancy supersaturation.

Main Results:

• Achieved measurement of vacancy concentrations around 10⁻⁷ at room temperature, decreasing to 10⁻⁹ after 3 hours.
• Demonstrated significant spatial variation of vacancy concentration, particularly near grain boundaries.
• Successfully assessed diffusion enhancement and determined vacancy supersaturation in sub-micrometer regions.

Conclusions:

• The cryogenic method effectively preserves excess vacancies, enabling detailed analysis of their distribution and role in microstructure evolution.
• This research advances the understanding and control of vacancies for enhanced strengthening of engineering alloys.
• The findings address critical gaps in measuring and mapping vacancies across various scales.