• Published May 1st, 2016

J.E. Schaffer, Ph.D., Senior Research and Development Engineer & S. Cai, PhD, Research and Development Engineer

In our July 2015 installment [1], we discussed Fort Wayne Metals’ recent development of a beta titanium, nickel-free superelastic alloy. At the time, as shown in Figure 1 below, we were able to design excellent shape setting response in linear wire segments, e.g. for applications such as kink-resistant guidewire and stylets. Straight shapeset geometries were achieved through conventional stress-annealing of a suspended wire segment as well as continuous reel-to-reel wire lengths. On the contrary, complex, e.g. Nitinol-like, wire forms require contact-fixtures as well as alternative heating modes and atmospheres that increase performance-specific design complexity. More recent developments, highlighted briefly in Figure 2, include specific processing techniques to shape set the same Ni-free alloy (code named RD149-16) into functional forms with varied mechanical behavior. Such forms can be designed and engineered in a “nitinol-like manner” to serve as dental files, orthodontic arch wires, textiles for stents, aneurysm-filling scaffolds, and other medical device forms where Nitinol is currently used.

Figure 1 – Elastic property tuning by shape-setting a single composition of beta Ti alloys at various temperature and time, from [1].

Figure 2 – Shape set processing results in Ni-free titanium beta alloy “RD149-16” showing (a) low plateau stress “low force” tuning; (b) high plateau stress “high force” tuning; and (c) a simple multi radius shape set form using 0.40 mm (0.016 in) wire with small and large bend radii of 0.50 and 3 mm respectively.

We welcome your next challenge! Fort Wayne Metals is your partner in not only alloy design, but also function-specific processing and product development. Our strength lies in many years’ hands-on experiences as well as our fundamental knowledge of material science and mechanical engineering [2-5].

References

[1] Bi-monthly Update: July 2015

[2] S. Cai, J.E. Schaffer, Y. Ren, “Deformation of a Ti-Nb alloy containing α"-martensite and omega phases”, Applied Physics Letters 106, 131907 (2015); doi: 10.1063/1.4916960

[3] S. Cai, J.E. Schaffer, C.Yu, M.R. Daymond, Y. Ren, "Evolution of Intergranular Stresses in a Martensitic and an Austenitic NiTi Wire During Loading–Unloading Tensile Deformation", Metallurgical and Materials Transactions A 2015, DOI 10.1007/s11661-015-2845-0

[4] S. Cai, J.E. Schaffer, Y. Ren and M.R. Daymond, “Discovery of a <210> fiber texture in medical-grade metastable beta titanium wire”, Acta Materialia 87 (2015) 390–398

[5] S. Cai, M.R. Daymond, Y. Ren, J.E. Schaffer, "Evolution of lattice strain and phase transformation in Beta III Ti alloy during room temperature cyclic loading", Acta Materialia, 61 (2013) 6830-6842

Click here to see previous highlights.

Disclaimer: Our monthly highlights are sneak peeks of what our R & D department is working on. This does not mean we have what is referenced above ready for manufacturing.