Influence of the ageing conditions and the initial microstructure on the precipitation of α phase in Ti-17 alloy

Abstract

The precipitation of rx phase during ageing was investigated in the near-� titanium alloy Ti-17 consid ering either a fully �metastable initial microstructure or a 35% r:J.primary + 65% �metastable initial micro structure. ln-situ electrical resistivity and high energy X-ray diffraction measurements revealed the influence of the initial microstructure, with different rx morphologies (size and distribution of rxprimary), as well as the heating rate on the precipitation sequences and kinetics following the decomposition of the �-metastable phase. Various amounts of metastable phases (Wisothermal and rx"1sotherma1) precipitate in temperature ranges that increase with the heating rate. From temperatures about 500 °C, the ortho rhombic rx"isothermal structure evolved towards the hexagonal close-packed rx as temperature increased. SEM microstructure characterisations showed that slow heating rates promoted a fine and dense rx precipitate distribution through the formation of Wisothermal and/or rx"isothermal, leading to higher hardness values. A higher heating rate restricted the precipitation of rx"1sotherma1 and shifted to the one of rx at a higher temperature, leading to coarser precipitates. Furthermore, precipitation kinetics of rx";sotherma1/rx were quicker considering an initial intragranular rx precipitation as compared to rx colonies.

On the effect of a thermal treatment on the tensile and fatigue properties of weak zones of similar Ti17 linear friction welded joints and parent material

“…Nonetheless, their application has found some limitations because of their high formulations and machining costs, complex processing [7], low production volumes, and property scatter [8]. The application of different thermal treatments leads to the precipitation of the α phase following different sequences and kinetics [9] and, in some cases, developing texture [10]. These precipitations have a substantial impact on the tensile strength of the alloy [11].…”

Characterization of the Anisotropy in the Microstructure and Mechanical Properties of Laser Powder Bed Fusion Ti6Al4V Alloys

“…The higher hardness of the LPBF Ti 6 Al 4 V components can be attributed to the formation of a large amount of fine and compact α′/α martensites during LPBF. [ 53,54 ]…”

“…The higher hardness of the LPBF Ti 6 Al 4 V components can be attributed to the formation of a large amount of fine and compact α 0 /α martensites during LPBF. [53,54] The microstructure of the X-Z plane is significantly different from that of the X-Y plane, which leads to obvious anisotropy in the tensile properties. Figure 11 demonstrates the stress-strain curves of Ti 6 Al 4 V components with different orientations.…”

Study of harmonic microstructure development during Spark Plasma Sintering (SPS) of β-CEZ titanium alloy

“…We considered the more commonly reported structure by using this technique [27] [28] i.e. the base centred orthorhombic α" iso , similarly to [29]. The present investigation cannot define if the structure is that of α", of a distorted α, or of O".…”