Bey Vrancken

Bio: Bey Vrancken is an academic researcher from Lawrence Livermore National Laboratory. The author has contributed to research in topics: Selective laser melting & Residual stress. The author has an hindex of 19, co-authored 31 publications receiving 2863 citations. Previous affiliations of Bey Vrancken include Katholieke Universiteit Leuven.

Effects of build orientation and heat treatment on the microstructure and mechanical properties of selective laser melted Ti6Al4V lattice structures

Abstract: The metal additive manufacturing industry is rising and so is the interest in new lattice structures with unique mechanical properties. Many studies have already investigated lattice structures with different geometries and their influence on mechanical properties, but little is known about the effect of specific processing characteristics that are inherent to metal additive manufacturing. Therefore this study investigates the effect of two crucial steps in the manufacturing process: the build orientation selection and heat treatment. In total the microstructure and static mechanical properties of five different orientations and three heat treatment conditions were evaluated using Ti6Al4V diamond like lattice structures. The results show a significant decrease in mechanical strength for samples that are built diagonally and a transformation of the microstructure after a HIP (hot isostatic pressing) treatment, resulting in a lower maximum strength, but higher ductility. In general, horizontal struts should be avoided during manufacturing, unless the applied load after manufacturing can be properly supported by other struts. Both a stress relief heat treatment and a HIP treatment can be used in statically loaded applications, whereas a HIP treatment is believed to be beneficial for dynamically loaded applications. This study enables an appropriate selection of build orientation and heat treatment of lattice structures for different applications.

Selective Laser Melting of Crack-Free High Density M2 High Speed Steel Parts by Baseplate Preheating

Abstract: Cracks and delamination, resulting from residual stresses, are a barrier in the world of additive manufacturing and selective laser melting (SLM) that prohibits the use of many metals in this field. By preheating the baseplate, thermal gradients are lowered and stresses can be reduced. In this work, some initial tests were performed with M2 high speed steel (HSS). The influence of preheating on density and mechanical and physical properties is investigated. The paper shows many promising results for the production of SLM parts in materials that are very sensitive to crack formation and delamination. When using a preheating of 200 � C, crack-free M2 HSS parts were produced with a relative density of 99.8%. [DOI: 10.1115/1.4028513]

The metallurgy and processing science of metal additive manufacturing

Abstract: Additive manufacturing (AM), widely known as 3D printing, is a method of manufacturing that forms parts from powder, wire or sheets in a process that proceeds layer by layer. Many techniques (using many different names) have been developed to accomplish this via melting or solid-state joining. In this review, these techniques for producing metal parts are explored, with a focus on the science of metal AM: processing defects, heat transfer, solidification, solid-state precipitation, mechanical properties and post-processing metallurgy. The various metal AM techniques are compared, with analysis of the strengths and limitations of each. Only a few alloys have been developed for commercial production, but recent efforts are presented as a path for the ongoing development of new materials for AM processes.

Additively manufactured hierarchical stainless steels with high strength and ductility

Abstract: Many traditional approaches for strengthening steels typically come at the expense of useful ductility, a dilemma known as strength-ductility trade-off. New metallurgical processing might offer the possibility of overcoming this. Here we report that austenitic 316L stainless steels additively manufactured via a laser powder-bed-fusion technique exhibit a combination of yield strength and tensile ductility that surpasses that of conventional 316L steels. High strength is attributed to solidification-enabled cellular structures, low-angle grain boundaries, and dislocations formed during manufacturing, while high uniform elongation correlates to a steady and progressive work-hardening mechanism regulated by a hierarchically heterogeneous microstructure, with length scales spanning nearly six orders of magnitude. In addition, solute segregation along cellular walls and low-angle grain boundaries can enhance dislocation pinning and promote twinning. This work demonstrates the potential of additive manufacturing to create alloys with unique microstructures and high performance for structural applications.