On the role of composition and processing parameters on the microstructure evolution of Ti-xMo alloys

Abstract

Laser Engineered Net Shaping (LENS™) was used to produce a compositionally graded Ti-xMo (0 ≤ x ≤ 12 wt %) specimen and nine Ti-15Mo (fixed composition) specimens at different energy densities to understand the composition–processing–microstructure relationships operating using additive manufacturing. The gradient was used to evaluate the effect of composition on the prior-beta grain size. The specimens deposited using different energy densities were used to assess the processing parameters influence the microstructure evolutions. The gradient specimen did not show beta grain size reduction with the Mo content. The analysis from the perspective of the two grain refinement mechanisms based on a model known as the Easton & St. John, which was originally developed for aluminum and magnesium alloys shows the lower bound in prior-beta grain refinement with the Ti–Mo system. The low growth restriction factor for the Ti-Mo system of Q = 6,5C 0 explains the unsuccessful refinement from the solute-based mechanism. The energy density and the grain size are proportional according to the results of the nine fixed composition specimens at different energy densities. More energy absorption from the material represents bigger molten pools, which in turn relates to lower cooling rates.

Review of the Design of Titanium Alloys with Low Elastic Modulus as Implant Materials

“…[ 143–145 ] Then the electron probe microanalysis (EPMA), X‐ray fluorescence, X‐ray diffraction, nanoindentation, and other techniques would be used to measure and obtain local compositions, crystal structures, and/or properties (e.g., hardness, elastic modulus, electrical conductivity, thermal expansion coefficients, and so on). This approach has been used in the design of many kinds of materials such as high‐entropy alloys, [ 146–149 ] bulk metallic glasses, [ 145,150–152 ] and Ti alloys [ 153–155 ] including those with a low elastic modulus. Teixeira et al [ 156 ] used a laser to deposit the pure Ti and pure Ta powders on a substrate to develop Ti–Ta alloys for biomedical applications.…”

“…electrical conductivity, thermal expansion coefficients, and so on). This approach has been used in the design of many kinds of materials such as high-entropy alloys, [146][147][148][149] bulk metallic glasses, [145,[150][151][152] and Ti alloys [153][154][155] including those with a low elastic modulus. Teixeira et al [156] used a laser to deposit the pure Ti and pure Ta powders on a substrate to develop Ti-Ta alloys for biomedical applications.…”

Additive Manufacturing of Ti-Alloys for Aerospace, Naval and Offshore Applications

“…The microstructure is defined by heat transfer, fluid dynamics, phase transformations and the thermophysical properties of the material. Knowing the microstructure evolution in AM is very important to determine the properties of the material (Mendoza et al [2019]). AM is a process that involves a condition that is far from thermodynamical equilibrium due to the rapid solidification.…”

“…Alloying elements such as boron (B) (Bermingham et al [2008]) and beryllium (Be) (Bermingham et al [2009]) acting as good grain refiners. All these efforts were focused on casting titanium alloys, but the fundamentals were extrapolated to additive manufacturing on titanium alloys for alloying elements such as molybdenum (Mo) (Mendoza et al [2019]) and tungsten (W) ). More recent research revealed the grain refiner power of lanthanum oxide (La 2 O 3 ) (Ng et al [2022]) and an hydrogenation treatment on wire arc additive manufacturing (WAAM) (Xiaolong et al [2022]).…”

A Review on Metallic Alloys Fabrication Using Elemental Powder Blends by Laser Powder Directed Energy Deposition Process

“…Here the research in DED-processed FGMs also helps to establish the process-structure-property relationship of these promising alloy systems. Ti-Cr [68], Ti-Al [69], Ti-W [70], and Ti-Mo [71] systems were also investigated. Details are tabulated in Table 1.…”