Microstructure and mechanical properties of a Ti6Al4V alloy recycled by waste chips vacuum arc melting

Abstract

Abstract This study investigated the microstructure and mechanical properties of the recycled Ti6Al4V alloy produced using the waste chips vacuum arc melting (VAM) process. The waste chips were cleaned to remove machining residues before VAM and dried in the oven. The dried and compressed chip compacts are vacuum arc melted and hot rolled. Microstructural characterization was performed by using an optical microscope, scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) analysis. Mechanical properties were determined by tensile and hardness tests. The microstructures of recycled Ti6Al4V alloy, which produced the VAM process, consist of acicular structures due to rapid solidification. After hot rolling from 950 °C, the elongated α grains and transformed β grains consisting of fine acicular α phase were observed. The recycled Ti6Al4V alloy by hot rolling after VAM exhibited very low total elongation compared to the as-received Ti6Al4V alloy. While a micro dimples ductile fracture was observed on the fracture surfaces of the as-received Ti6Al4V alloy after the tensile test, a brittle fracture surface was observed in the recycled Ti6Al4V alloy samples after VAM + hot rolling due to the coarse α and β grain structure after cooling in the air after hot rolling.