Dislocation substructures in pure aluminium after creep deformation as studied by electron backscatter diffraction

Area of Science:

• Materials Science
• Metallurgy
• Solid Mechanics

Background:

• Creep is a critical deformation mechanism in metals under sustained stress at high temperatures.
• Understanding dislocation structures is key to predicting material behavior and failure.
• Pure aluminum (99.8%) serves as a model material for studying fundamental creep mechanisms.

Purpose of the Study:

• To investigate the microscopic dislocation structures formed during steady-state creep in pure aluminum.
• To analyze the influence of crystallographic orientation and stress levels on these structures.
• To elucidate the role of intergranular stresses in dictating subgrain formation density.

Main Methods:

• Electron backscatter diffraction (EBSD) for analyzing microscopic dislocation structures.
• Controlled creep tests at steady state under two distinct stress levels (power-law and power-law breakdown regimes).
• Microstructural analysis of pure 99.8% aluminum samples.

Main Results:

• Subgrain cellular structure formation is independent of crystallographic orientation.
• The density of cellular structures is highly dependent on grain orientation relative to the tensile axis.
• 〈111〉 oriented grains exhibited the highest densities of cellular structures at both stress levels.
• 〈001〉 grains showed lower densities compared to 〈111〉 grains.

Conclusions:

• Crystallographic orientation significantly influences dislocation structure density during creep in pure aluminum.
• Intergranular stresses play a crucial role in the observed orientation-dependent density of subgrain cellular structures.
• The findings contribute to a deeper understanding of creep mechanisms in face-centered cubic metals.