Fatigue of titanium alloy Ti6Al4V with diamond structure obtained by Laser Power Bed Fusion method

Abstract

This paper presents the results of fatigue tests conducted on Ti6Al4V titanium alloy with diamond structure obtained by the Laser Power Bed Fusion method. Samples used in tests were printed with porosities: 81%, 73%, 50%, 34% and near-zero porosity. Samples were subjected to cyclic tests with a constant stress amplitude. The number of cycles until sample failure was registered. Obtained fatigue test results made it possible to determine simple, semi-empirical dependencies making it possible to forecast the fatigue life of Ti6Al4V titanium alloy with diamond structure obtained by the Laser Power Bed Fusion method under conditions of uniaxial, cyclically variable loads. The experimental results revealed that the initiation of the macro-crack occurred already with a small number of cycles. This was caused by the presence of two types of notches: technological micro-notches between particles of melted powder and notches related to the shape of the diamond structure itself. Microscopic observations of the fatigue fractures of samples were carried out, both on those subjected to low-cycle tests and those subjected to high-cycle tests. This made it possible to identify crack initiation and damage accumulation mechanisms as well as to propose numerical dependencies for samples of the tested structure. For this purpose, it is necessary to determine only the tensile strength of the given metamaterial and the fatigue characteristic for the given porosity.