Effect of DMLS Parameters and Heat Treatment on the Microstructure, Mechanical Performance, and Biofunctionality of Ti-6Al-4V Alloy

Abstract

 Introduction: Metallic biomaterials are widely applied in reconstructive surgery, including joint arthroplasty, maxillofacial surgery, and dentistry. Titanium alloys, particularly Ti-6Al-4V, are of special interest due to their low density, favorable mechanical properties, high corrosion resistance, and biocompatibility. Conventional processing methods, such as casting and plastic forming, are costly and technically challenging. In recent years, additive manufacturing technologies, especially Direct Metal Laser Sintering (DMLS), have emerged as promising alternatives.

 Aim: The study aimed to verify the hypothesis that proper adjustment of DMLS manufacturing parameters, combined with heat treatment, enables the production of Ti-6Al-4V elements with high density, controlled microstructure, low porosity, and mechanical properties comparable to those obtained by conventional methods.

 Materials and Methods: Ti-6Al-4V alloy specimens were fabricated using DMLS under varying laser power and scanning speed conditions. Heat treatments at different temperatures were performed to modify the as-sintered martensitic microstructure. Mechanical properties (Rm, Re, A, E), surface roughness, porosity, and microstructure were evaluated. Additionally, biofunctionality and cytotoxicity in simulated body fluids were assessed.

 Results: Laser power and scanning speed significantly affected surface roughness and material density. Mechanical properties were strongly correlated with energy density and post-processing heat treatment. The as-sintered martensitic microstructure provided high strength but insufficient ductility and ferromagnetism, thus unsuitable for biomedical use. Heat treatment at 850 °C for 2 hours resulted in a two-phase microstructure with improved ductility, homogenized structure, and reduced anisotropy, while porosity remained nearly unchanged (< 0.5% at 100–127 J/mm³ energy density). Mechanical parameters Rm and Re decreased, whereas A and E increased, reflecting enhanced functional balance.

 Conclusion: Optimized DMLS parameters combined with appropriate heat treatment allow the production of Ti-6Al-4V implants with desirable mechanical and structural characteristics, ensuring biofunctional performance comparable to conventionally processed alloys.