In-situ alloying of Ti-5Fe titanium alloy using direct powder forging and the effect of the powder mixing method

Abstract

This study investigates direct powder forging (DPF) as a new approach for the consolidation and in-situ alloying of the titanium alloy Ti-5Fe from loose powder. The absence of green compaction before thermomechanical processing and the effect of the powder blending method have been found to significantly influence the chemical and microstructure homogeneity. Two different powder mixing techniques were compared, ball milling (BM) and blended elemental (BE). After the initial heating stage, the BM sample has a uniform α+β lamella microstructure within the particles with a homogeneous iron distribution, unlike the BE sample, which shows a heterogeneous lamella microstructure, retained β-Ti (Fe-rich) and TiFe intermetallic compounds. Even if the BM samples exhibit a slightly higher density over the BE samples after the initial heating stage, all samples achieved full density and had a α+β lamella microstructure after the thermomechanical steps. However, for the BE sample, even if the DPF process was able to eliminate the intermetallic compounds, the thermomechanical process did not homogenize the iron, resulting in a heterogeneous and coarser microstructure. Based on the results, it can be concluded that DPF using a BM technique led to a fully homogenous and fully consolidated Ti-5Fe alloy. Therefore, direct powder forging has significant potential as an alternative fabrication strategy to produce the Ti-5Fe alloy. Moreover, this work can expand the opportunities for the development of the promising Ti-5Fe alloy.