On the effect of throughout layer thickness variation on properties of additively manufactured cellular titanium structures

Over the past two decades, additive manufacturing has opened a new window of opportunities in fabricating complex porous matrix structures such as cellular solids. Several factors including design, material and process parameters can selectively be varied to tailor the porous properties of products based on the intended application. This article addresses the effect of variable throughout layer thickness configuration in the binder-jet additive manufacturing of titanium structures for orthopedic applications. Two layer thicknesses of 80 and 150 μm are selectively controlled inside of each titanium sample with four different configurations. Several studies were performed, including shrinkage analysis, porosity measurements, and mechanical compression tests to quantify the effect of layer thickness on part quality and mechanical properties. The results of the porosity measurement revealed that there is about 5% variation among the samples with different layer thickness configuration. Bulk porosity values obtained from micro computed tomography (μCT) scan data placed the bulk porosity of the samples combining more than one layer thickness, in between of the results for control specimens, which were manufactured by applying a single layer thickness throughout the samples. Mechanical properties did not show any significant variation, which is attributed to the low range of the porosity deviation (less than 5%). The highest Young's modulus of 3.50 ± 0.4 GPa and yield stress of 175 ± 25 MPa were obtained from analysis of the data achieved from the compression test.