The Effects of Geometry Size and Initial Microstructure on Deformation Behavior of Electrically-Assisted...

Area of Science:

• Materials Science
• Mechanical Engineering
• Metallurgy

Background:

• Electrically-assisted micro-compression (EAMC) is a technique used to study material behavior under combined mechanical and electrical loading.
• Ti-6Al-4V alloy is a widely used titanium alloy in aerospace and biomedical applications.
• Understanding the influence of microstructural and geometric parameters on EAMC is crucial for optimizing its performance.

Purpose of the Study:

• To investigate the effects of geometric size and initial microstructure on the mechanical response of Ti-6Al-4V during EAMC.
• To quantify the relationship between current density, Joule heat, and specimen temperature.
• To analyze the influence of Joule heating and microstructural characteristics on the flow stress and deformation behavior of Ti-6Al-4V.

Main Methods:

• Cylindrical Ti-6Al-4V specimens of four geometric sizes and three initial microstructures were subjected to EAMC tests.
• Specimen temperature was monitored, and a quasi-static heat equilibrium equation was developed to analyze Joule heat effects.
• Microstructural analysis was performed to correlate phase transformations and grain structures with mechanical properties.

Main Results:

• Specimen temperature increased nonlinearly with the square of current density.
• Joule temperature scale effect had a greater impact on flow stress than sample size.
• A 0.5 mm diameter sample exhibited abnormal deformation due to surface oxidation.
• α→β phase transformation occurred below the β transus temperature due to local Joule heating.
• Widmannstatten microstructure showed higher strength and easier flow localization than basket-weave microstructures.

Conclusions:

• Joule heating and microstructural features significantly influence the mechanical properties of Ti-6Al-4V during EAMC.
• Specimen geometry and surface conditions play a role in deformation behavior.
• The study provides insights into the complex interplay between electrical current, heat generation, and material microstructure in micro-compression testing.