Development of strength-hardness relationships in additively manufactured titanium alloys

Abstract

A major concern for additively manufactured (AM) Ti-6Al-4V components is how AM processing parameters and post-process heat treatments impact the resulting mechanical behavior. The applicability of using microhardness measurements as a predictive tool for yield and tensile strengths of AM Ti-6Al-4Vwould provide a rapid and useful screening mechanism for ensuring that properties meet requirements in complex geometries. However, microhardness measurements on Ti-6Al-4V exhibit high levels of data variability due to the orientational impact of the α phase. In order to overcome this variability in hardness measurements, a methodology

An Overview of Additive Manufacturing of Titanium Components by Directed Energy Deposition: Microstructure and Mechanical Properties

“…Despite a similar microstructure in both laser and electron beam DED, the scale of these microstructure characteristics varied depending on the AM process. It was reported that the microstructure of electron beam based DED is coarser with respect to the laser based one [59,82]. Liu et al suggested the development of grain morphology during the direct laser deposition of different geometries ( Figure 2).…”

“…This specific orientation is explained by the direction of heat conduction during the direct laser deposition [28]. It was found that the different processing and post-process conditions were expected to result in various microstructures and a wide range of mechanical properties [82][83][84]. For instance, the microstructure of components produced by laser or electron beam based DED in as deposited condition exhibited a lamellar α + β structure.…”

Application of Directed Energy Deposition-Based Additive Manufacturing in Repair

“…Apart from the application of DED as a coating technique, this technology has intensively been employed as a manufacturing technology [4,42,43]. Over the past decade, DED could attract more attention regarding its capability in the fabrication of parts with complex geometries to near-net-shape, with the high cost and material savings.…”

The Hardness of Additively Manufactured Alloys

“…The addition of Al stabilizes the α phase while V stabilizes β. Generally, as-deposited microstructures after powder bed fusion (PBF) AM exhibit a fine martensitic (α') structure with acicular laths while the microstructures in directed energy deposition (DED) AM typically have a coarser structure consisting of lamellar α and small amounts of β [80]. Figure 18 Figure 19, which shows a decrease in hardness with the coarsening of the lath for DED-L and PBF-EB.…”

“…The works of Tabor [112] and Cahoon [113] have shown that hardness is directly proportional to yield strength. Recently, Keist and Palmer [80] investigated the strength-hardness relationships for the DED of Ti-6Al-4V using both laser and electron beam heat sources. Their correlation is plotted along with independent experimental data for Ti-6Al-4V components fabricated by PBF and DED processes in Figure 20.…”