Low-Cycle Fatigue Behavior of Wire and Arc Additively Manufactured Ti-6Al-4V Material

Area of Science:

• Materials Science
• Mechanical Engineering
• Additive Manufacturing

Background:

• Additive manufacturing (AM) offers advantages in producing complex structures.
• Wire Arc Additive Manufacturing (WAAM) produces components with distinct microstructures and properties compared to substrates.
• Understanding WAAM material behavior is crucial for fatigue-critical applications.

Purpose of the Study:

• To investigate and compare the mechanical behavior and fatigue performance of WAAM-fabricated Ti-6Al-4V against its substrate.
• To analyze the microstructure and identify failure mechanisms.
• To evaluate and compare predictive models for cyclic deformation and fatigue life.

Main Methods:

• Tensile and low-cycle fatigue (LCF) testing of WAAM and substrate Ti-6Al-4V.
• Microstructural analysis using optical microscopy and scanning electron microscopy (SEM).
• Fitting experimental data to Ramberg-Osgood and Manson-Coffin-Basquin models.

Main Results:

• WAAM Ti-6Al-4V exhibited a coarser, heterogeneous microstructure with more defects, lower tensile strength, and reduced elongation.
• LCF tests showed lower fatigue strength in WAAM material, with cracks initiating at pores.
• WAAM material properties were generally lower than powder-based AM processes; a universal material law effectively estimated strain-life behavior.

Conclusions:

• WAAM Ti-6Al-4V possesses inferior quasi-static and fatigue properties compared to the substrate.
• Crack initiation in WAAM material is often linked to process-induced defects.
• Further research is needed to optimize WAAM process parameters for improved mechanical and fatigue performance.