A novel direct reduction and alloying process for making additive manufacturing of titanium alloys greener

Abstract

Additive manufacturing (AM) is considered an energy-efficient alternative to conventional subtractive manufacturing of metals. However, the high embodied energy of the feed materials undermines the merits of energy saving in AM. Spherical Ti-6Al-4V alloy powder, widely used in AM, is commercially produced by atomizing Ti alloys made from the Kroll process. This production route incurs high energy consumption due to low yield, the energy required to melt and break the molten metal into fine particles and make the primary titanium metal. This paper presents a novel, energy-efficient pathway for directly fabricating spherical Ti-6Al-4V alloy powder from oxides. In this process, raw metal oxides are reduced to form fine Ti-6Al-4V alloy powder, which is then granulated, sintered, and deoxygenated to produce the low-oxygen spherical powder. The integrated process is called the direct reduction and alloying (DRA) process. Spherical Ti-6Al-4V alloy powders produced by this process have low interstitial impurities, controlled particle size distribution, homogeneous compositions, and excellent flowability for AM applications. Energy consumption analysis suggests that the DRA process has the potential to significantly reduce the energy consumption of producing titanium alloy feedstock, thereby improving the environmental impact of additive manufacturing.