Influence of Voids on Fatigue Life of 3D Printed Titanium Alloy Specimens

User Benefits

- Internal voids due to 3D printing manufacturing processes can be visualized with the CT scan - Fatigue fracture due to internal voids can be tested rapidly thanks to the ultra-sonic test frequency - Analysis of the influence of voids on fatigue life made possible by determining void location with surface fracture analysis and correlating with cycles to failure

Introduction

The titanium alloy Ti6Al4V is characterized by high specific strength, good corrosion resistance and biocompatibility, and it is mainly used in prosthesis and aircraft industry related parts. As an alternative technology to fabricate such components, 3D printing (or additive manufacturing, AM) is increasingly drawing more interest. Compared to traditional manufacturing techniques such as machining or forging, 3D printing offers several advantages such as higher degree of freedom of the component shape, a shorter fabrication time, etc . Among the available 3D printing techniques, the most used for metallic materials is the PBF (Powder Bed Fusion). An image of the fabrication process with electron beam PBF (E-PBF) is represented. In contrast to its advantages, 3D printed materials tend to exhibit more internal voids (trapped gas or lack of fusion). For this reason, to enhance the reliability of 3D printed components the correlation between the characteristics of internal defects (distribution, size, position, etc.) with the fatigue strength must be analyzed. In this article, the results of an analysis conducted with 3 different instruments using samples fabricated via electron beam PBF are presented. Firstly, a CT scan was conducted on the samples to visualize and measure the size of internal voids. Afterwards, the fatigue strength of the specimens was analyzed by using an ultrasonic testing machine. Finally, the fracture surface has been observed with an electron probe microanalyzer (EPMA) to detect the crack initiation site. A correlation between the void position and the fatigue strength could be obtained.

26 de diciembre de 2023 GMT