Disorder trapping during crystallization of the B2-ordered NiAl compound.

Area of Science:

• Materials Science
• Computational Materials Science
• Alloy Solidification

Background:

• Disorder trapping during solidification is a critical phenomenon affecting material properties.
• Understanding defect formation mechanisms in ordered alloys like B2 NiAl is essential for controlling microstructure.
• Previous models may not fully capture the complexity of defect trapping at high solidification rates.

Purpose of the Study:

• To investigate disorder trapping during the solidification of B2 NiAl.
• To analyze the formation and distribution of defects (antisite defects and vacancies) at various growth directions.
• To examine the relationship between interface velocity and defect concentration.

Main Methods:

• Utilizing molecular dynamics simulations to model the solidification process.
• Studying the (100), (110), and (111) crystallographic growth directions.
• Quantifying the concentrations of vacancies and antisite defects.

Main Results:

• Observed significant disorder and defect trapping (antisite defects and vacancies) at high interface velocities.
• Identified vacancies primarily on the Ni sublattice and Ni antisite defects on the Al sublattice.
• Found a near-linear relationship between defect concentration and interface velocity.
• Determined no significant anisotropy in defect concentrations for different growth orientations.

Conclusions:

• The study confirms pronounced disorder and defect trapping in B2 NiAl during rapid solidification.
• Results indicate that current disorder trapping models need enhancement to incorporate both antisite defects and vacancies.
• The findings provide crucial insights for predicting and controlling alloy properties under non-equilibrium solidification conditions.