Phase evolution in laser-deposited titanium-chromium alloys

Abstract

Ti-Cr alloys have been laser deposited from powder feedstock consisting of a blend of elemental powders using the laser-engineered net-shaping (LENS) process. The microstructure of the as-deposited Ti-Cr alloys primarily consists of a metastable bcc matrix of ␤ -Ti(Cr) with precipitates along the grain boundaries. The grain-boundary precipitates have been identified to be of three types, essentially pure hcp Ti, an alloyed hcp phase designated ␣ -Ti(Cr), and the C14 TiCr 2 Laves phase. Initial stages of decomposition, visible within the ␤ matrix, suggest a spinodal clustering process resulting in a fine dispersion of second phases. Diffraction studies have revealed the presence of fine precipitates of ␣ within the ␤ matrix. The evidence for the precipitation of the metastable phase within the ␤ matrix is not strong. The phase evolution in the LENS-deposited Ti-Cr alloy has been discussed in the context of rapid solidification and the enthalpy of mixing of the elemental powders.

Laser Deposition of In Situ Ti – TiB Composites

“…The advantages of a negative enthalpy of mixing in the LENS TM deposition of alloys from elemental powder blends has been discussed in previous papers. [7][8][9] One of the significant advantages of LENS TM processing is its ability to produce fully dense, near-net shape components of intricate design in a single step. Thus, combining these advantages of the LENS TM technology with the use of inexpensive elemental powders as the feedstock offers an attractive processing route for near-net shape high strength Ti-TiB composites.…”

“…Since, titaniumbase alloys have wide ranging applications in the aerospace industry where the LENS TM technology affords a competitive processing route for the manufacturing of components of intricate design, recent experiments have been carried out using elemental powder blends containing Ti as the primary component. [7,8] The results suggest that one of the important factors determining the microstructure and compositional homogeneity in alloys deposited from elemental blends is the enthalpy of mixing of the constituent elements. The present research explores the feasibility of depositing in situ metalmatrix composites consisting of a Ti-alloy matrix with TiB precipitates, starting from a blend of elemental Ti (or pre-alloyed Ti) powder and elemental boron powder using the LENS TM process.…”

“…There have been only a limited number of studies on the laser deposition of alloys from elemental powder blends. [5][6][7][8][9] Takeda et al [5] and Steen Due to their enhanced mechanical properties and potentially wide applicability, there is considerable interest in the development of metal-matrix composites consisting of titanium borides in a titanium alloy matrix. Despite the development of a variety of different processing routes for these composites, there are relatively few ones capable of processing a fully dense, near-net shape component with a relatively fine dispersion of boride precipitates.…”

Laser deposition and deformation behavior of Ti–Nb–Zr–Ta alloys for orthopedic implants

“…Such an additive manufacturing process is expected to have a substantial impact on the development of the next generation orthopedic implants, as it can rapidly and efficiently manufacture custom-designed complex implants but also functionally-grade them to exhibit required site-specific properties (Hedges, 2003). Recent experiments demonstrate the success in depositing homogeneous alloys and metal-matrix composites, primarily from pre-alloyed powder feedstock, using LENS TM (Griffith et al, 1999;Schwendner et al, 2001;Banerjee et al, 2002a;Banerjee et al, 2002b;Collins et al, 2003).…”

Optical transparency, thermal resistance, intermolecular interaction, and mechanical properties of poly(styrene‐butadiene‐styrene) copolymer‐based thermoplastic elastomers

“…Since the LENS process uses a powder feedstock, it allows the flexibility to deposit blends of elemental powders to create alloys in situ . Recent experiments demonstrate the success in depositing homogeneous alloys and metal‐matrix composites with refined microstructures using LENS 4–7…”