Abstract
A selective laser melting (SLM)-based, additively-manufactured Ti-6Al-4V alloy is prone to the accumulation of undesirable defects during layer-by-layer material build-up. Defects in the form of complex-shaped pores are one of the critical issues that need to be considered during the processing of this alloy. Depending on the process parameters, pores with concave or convex boundaries may occur. To exploit the full potential of additively-manufactured Ti-6Al-4V, the interdependency between the process parameters, pore morphology, and resultant mechanical properties, needs to be understood. By incorporating morphological details into numerical models for micromechanical analyses, an in-depth understanding of how these pores interact with the Ti-6Al-4V microstructure can be gained. However, available models for pore analysis lack a realistic description of both the Ti-6Al-4V grain microstructure, and the pore geometry. To overcome this, we propose a comprehensive approach for modeling and discretizing pores with complex geometry, situated in a polycrystalline microstructure. In this approach, the polycrystalline microstructure is modeled by means of Voronoi tessellations, and the complex pore geometry is approximated by strategically combining overlapping spheres of varied sizes. The proposed approach provides an elegant way to model the microstructure of SLM-processed Ti-6Al-4V containing pores or crack-like voids, and makes it possible to investigate the relationship between process parameters, pore morphology, and resultant mechanical properties in a finite-element-based simulation framework.
Highlights
Already being a well-established manufacturing process in the production of polymer-based components, Selective laser melting (SLM) of metal powders for producing near net-shape components has recently gained increased attention
Recent activities have focused on the processing of titanium alloys, such as Ti-6Al-4V, which is used for the fabrication of components with complex geometry, as required in biomedical and aerospace applications
Thermal post-treatment may cause phase transformations and variations in grain morphology [5], while improper process parameters result in voids and crack-like defects showing complex geometrical features [4]
Summary
Already being a well-established manufacturing process in the production of polymer-based components, Selective laser melting (SLM) of metal powders for producing near net-shape components has recently gained increased attention. The identification of suitable alloys and raw powders, and the optimization of the process parameters to obtain defect-free, high-strength components with desired mechanical properties, are topics of active research [1]. With regard to the Ti-6Al-4V alloy, the SLM process parameters and thermal history are known to significantly affect microstructure formation [2,3,4]. The microstructure, voids and defects, governs the effective mechanical properties of the manufactured components, such as tensile or fatigue strength [6,7,8,9].
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