Effect of Sn on microstructure and mechanical properties of Ti-base dendrite/ultrafine-structured multicomponent alloys

Abstract

Ti 57Ϫx Cu 15 Ni 14 Sn 4ϩx Nb 10 (x ϭ 0, 5, or 10) alloys were prepared by copper mold casting. At Sn ϭ 4 at. pct, a dendrite/ultrafine-structured multicomponent alloy was obtained, which exhibits 1271 MPa yield strength, 77 GPa Young's modulus, and 2 pct plasticity at room temperature for 3-mm-diameter samples. The cooling rate significantly affects the as-cast microstructure and the mechanical properties. For 5-mm-diameter samples, the alloy exhibits 1226 MPa yield strength, 63 GPa Young's modulus, and 2.5 pct plasticity. At Sn ϭ 9 at. pct, Ti-, Sn-, and Nb-rich particles precipitate primarily. This near-hypereutectic alloy composition leads to the precipitation of intermetallics, which deteriorate the mechanical properties and result in the coexistence of ductile and brittle fracture mechanisms. At Sn ϭ 14 at. pct, the alloy composition is completely in the intermetallic region, thus inducing the formation of Ti 2 Cu, Ti 2 Ni, and Ti 3 Sn intermetallics. The alloy becomes very brittle because the intermetallic compounds dominate the fracture process.

Diffusion bonding of Ti–2.5Al–2.5Mo–2.5Zr and Co–Cr–Mo alloys

“…7b) and the latter displays a 'tearing up' mechanism (Fig. 7c) which can be frequently found in the fractographs of Ti alloys with mixture of ␣ or ␤ and intermetallics [13][14][15]. Such mixed microstructure usually exhibits very limited plasticity.…”

Structure Formation and Mechanical Behavior of Two-phase Nanostructured Materials

“…[182] Probably, a high amount of Ta (~50 at%) significantly promotes the formation of α′ and α″ martensite in the β-Ti phase. [185] Increasing the Sn content from 4 to 9 at% shifts the alloy composition from a hypo-to a hyper-eutectic microstructure, as illustrated in Figure 13.29(c). It has been suggested that the deformation mechanism and the pronounced cold workability of near beta Ti(Nb, Ta)-alloys is also linked to the formation of deformation twins on a nanometer lengthscale.…”

“…[185] These alloys (S1: x = 0, S2: x = 5, S3: x = 10) are located in the pseudo-ternary phase formation diagram ( Fig. [185] These alloys (S1: x = 0, S2: x = 5, S3: x = 10) are located in the pseudo-ternary phase formation diagram ( Fig.…”

“…It has been suggested that the deformation mechanism and the pronounced cold workability of near beta Ti(Nb, Ta)-alloys is also linked to the formation of deformation twins on a nanometer lengthscale. [185] For 14 at% Sn (S3), the composition of the alloy completely shifts to the intermetallic area, yielding different intermetallics in the as-solidified microstructure ( Fig. [184] It can be clearly seen from Figure 13.56 that there is an increase in the plastic deformability and a decrease in the yield strength with increasing volume fraction of dendrites in the different alloys.…”

“…The important phenomenon noticed in these alloys is a significant change in the transition behavior from elastic to plastic deformation. [185] 13: Structure Formation and Mechanical Behavior, Eckert 653 Regarding the "biocompatible" nanostructure-dendrite composites, the Co-(Ti 60 Cu 14 Co 12 Sn 4 Nb 10 ) and Fe-containing (Ti 74 Cu 8 Fe 6 Sn 2 Nb 10 ) alloys exhibit low elastic moduli (E) of 67 and 54 GPa, respectively, similar to (E = 55 GPa) for the well-known Ti-35Nb-7Zr-5Ta (wt%) alloy. Very similar mechanical properties were also observed when substituting Nb by Mo.…”