Defect-based characterization of the fatigue behavior of additively manufactured titanium aluminides

TL;DR

This study investigates the fatigue behavior of additively manufactured titanium aluminides, focusing on defect characterization and the effects of hot isostatic pressing, revealing significant improvements in fatigue strength and predictive modeling of fatigue life.

Contribution

It introduces a detailed defect-based analysis of fatigue behavior in additively manufactured titanium aluminides and applies model approaches to predict fatigue life based on defect characteristics.

Findings

Fatigue strength increased by 43% after HIP treatment.

Defect size and number reduction improved fatigue life.

Fatigue life correlated with local stress intensity factors.

Abstract

The additively manufactured titanium aluminide alloy TNM-B1 was characterized microstructurally and mechanically in the as-built and hot isostatically pressed (HIP) condition. Tensile and constant amplitude tests were performed at room temperature and 800 {\deg}C. Using fractographic SEM images, the fracture-inducing defect was identified. With the HIP, defect number and size could be reduced, increasing fatigue strength by 43% to 500 MPa. Using the model approaches of Murakami and Shiozawa, the fatigue life was correlated with the local stress intensity factor and could be described as function of the stress amplitude as well as the size and location of fracture-inducing defects.