Selective laser manufacturing of Ti-based alloys and composites: impact of process parameters, application trends, and future prospects

Aviation and automobile industries demand high strength, fatigue resistant, and wear-resistant materials in combination with lightweight, especially for structural applications. On the other hand, biomedical applications demand materials with low modulus and stiffness for optimized implants better matching the modulus of human bone combined with enhanced strength and wear resistance. For all the aforementioned applications in various fields, the fabrication of parts with desired size and shape without the need for joining or welding operations is desired while simultaneously reaching improved mechanical properties and more resistance to environmental attack, which are stringent requirements for almost all the applications. To achieve all these demands, both material developments, as well as modification of process conditions and parameters, are essential. Along these lines, a lot of research work focusses on advanced or even disruptive manufacturing routes and proper alloy development (e.g. Ti, Al, steels, and so on) applying additive manufacturing (AM) techniques for various applications. Among different AM methods, selective laser melting (SLM) is in high demand and preferred for achieving fully dense products in the required dimensions. Titanium alloys designed for AM have replaced a variety of other alloys due to their superior properties such as lightweight or good fatigue and corrosion resistance, achievable through modified microstructures gained by the faster heating and cooling rates realized upon laser printing. Ti alloys with a single (α) or dual (α+β) microstructure are mostly implemented in the aviation and automobile industries, whereas β alloys with exceptionally low modulus close to that of human bone are intensively studied for bio and dental implants but have not been commercialized yet. The modification of microstructure and properties in Ti-based materials with the addition of suitable reinforcement is also a reliable method. In this article, critical aspects for the optimization of processing parameters affecting the properties of SLM manufactured Ti alloys and titanium matrix composites (TMCs) will be presented, and future prospects of such materials will be critically assessed. This work is expected to be helpful for future studies on Ti alloys and composites with enhanced properties processed by laser manufacturing.