The Wire Drawing Mechanics of Near-Equiatomic NiTi SMA

Abstract

The wire drawing mechanic of Ti-49.82Ni (at. %) Shape Memory Alloy (SMA) was investigated through the true stress-strain curves and drawing stresses. The tensile tested solution treated wire presented a four steps elongation at temperatures below the austenite finish temperature (A F), and a conventional one-step behavior above the martensite deformation temperature (M D). The tensile yield stress for the formation of detwinned martensite (DTM) or stress-induced martensite (SIM) increased as the testing temperature increased; however, for larger deformation, the behavior reversed. The efficiency of drawing work, which is the ratio of uniform work to total work, increased from 10% for 0.07 mm 2 .mm-2 area reduction at 25 °C to 50% for 0.21 mm 2 .mm-2 at 110 °C. Therefore, wire drawing temperature and area reduction should be combined to increase the efficiency, taking into account the desired properties with reasonable workability. Furthermore, transformation work should be considered on wire drawing shape memory alloys as phase transformation occurs in temperatures below M D .

The influences of the variable speed and internal die geometry on the performance of two commercial soluble oils in the drawing process of pure copper fine wire

“…The inhomogeneous additional work component is closely related with the die geometry, diminishing when the approach angle is lower. For a low area reduction, most of the energy is spent as friction work, and the redundant work is relatively low 1 Geometric variables and the main zones in the wiredrawing process when 2 < ∆ < 3 [3]. Under normal conditions, friction effect constitutes nearly 20% of loses while 12% is due to the additional-redundant work.…”

“…Many previous works consulted demonstrated the great importance of knowing reliably the value of the friction coefficient µ to be able to study analytically or numerically the wiredrawing process. It is so that, by the use of numerical models and methods, Chen and Huang [3] and Majzoobi et al [4] determined that 2β, Hc and the temperature profile into the die have a significant effect on the drawing process, but it is very important to consider the effect of the wire-die contact length (l) which determines the contact surface at the interface and has a direct effect on the lubrication conditions and, as a consequence, on the value of the friction coefficient µ, involved in the process. Another consulted works demonstrated the feasibility of the use of FEM applied to model the wiredrawing process and focused on the improvement of the geometry of the die [13], on the analysis of the strain distribution in the wire during the process [14] or even to analyze the distribution of residual stresses accumulated in the product once it has been shaped [15], among other output variables.…”

Effect of Cold Drawing and Annealing in Thermomechanical Treatment Route on the Microstructure and Functional Properties of Superelastic Ti-Zr-Nb Alloy

“…Drawing is successfully used for the efficient processing of metallic biomaterials based on zinc [ 23 , 24 ], magnesium [ 25 ], titanium [ 26 , 27 ], and titanium nickelide [ 18 , 28 , 29 , 30 ]. It has been shown that CD of biodegradable Zn- and Mg-based alloys yields control of grain refinement, phase composition, and crystallographic texture to improve strength properties and corrosion behavior [ 23 , 24 , 25 ].…”

“…High-temperature deformation, which makes it possible to carry out multi-pass drawings, seems to be more preferable for processing Ti-6Al-4V alloys and promotes grain refinement due to dynamic recrystallization and a corresponding increase in the strength of the alloy [ 31 ]. Multi-pass cold drawing, combined with thermal treatment, is effectively used to manufacture thin Ni-Ti wires for vascular stapling and orthodontics [ 28 , 29 ]. The nanocrystalline state with precipitation of dispersed Ti 3 Ni 4 particles, provided by controlled PDA after CD, makes it possible to achieve abnormally high recovery strains in the thin Ni-Ti wire [ 32 ].…”