Elevated-Temperature Tensile Properties of Low-Temperature HIP-Treated EBM-Built Ti-6Al-4V

Area of Science:

• Materials Science
• Additive Manufacturing
• Metallurgy

Background:

• Titanium alloy Ti-6Al-4V is crucial in aerospace and biomedical applications.
• Electron beam melting (EBM) is a common additive manufacturing technique for Ti-6Al-4V.
• Hot isostatic pressing (HIP) is used to improve mechanical properties and microstructure of additively manufactured parts.

Purpose of the Study:

• To evaluate the high-temperature tensile properties of EBM-manufactured Ti-6Al-4V.
• To compare the effects of a low-temperature HIP (800 °C) versus standard HIP (920 °C) treatment.
• To investigate the microstructural evolution under different thermal treatments.

Main Methods:

• Tensile testing of Ti-6Al-4V specimens at room temperature and elevated temperatures (up to 350 °C).
• Metallurgical characterization using microscopy to analyze microstructural changes (e.g., α lath width, β grain width).
• Comparison of as-built, low-temperature HIP, and standard HIP conditions.

Main Results:

• Low-temperature HIP (800 °C) resulted in finer α laths compared to standard HIP (920 °C).
• Standard HIP treatment led to a 10-14% reduction in yield strength compared to as-built and low-temperature HIP conditions.
• Yield strength decreased significantly at 350 °C for all conditions, while ductility showed complex behavior with an initial increase at 150 °C followed by a decrease.

Conclusions:

• Low-temperature HIP treatment preserves finer microstructures and enhances yield strength in EBM Ti-6Al-4V at elevated temperatures.
• Standard HIP treatment at 920 °C negatively impacts yield strength due to increased α lath width.
• Understanding the interplay between HIP temperature, microstructure, and high-temperature mechanical performance is critical for optimizing EBM Ti-6Al-4V components.