title: Microstructures of beta-titanium orthodontic wires joined by infrared brazing.
abstract: The microstructures and interdiffusion in brazed beta-titanium orthodontic wires were investigated by scanning electron microscopy and electron probe microanalysis, respectively. Beta-titanium wire (Ti-11Mo-6Zr-4Sn) with cross-section dimensions of 0.032 in. x 0.032 in., titanium-based braze alloy (Ti-30Ni-20Cu), and silver-based braze alloy (Ag-22Cu-17Zn-5Sn) were selected for the study. Brazing was performed using infrared radiation (RS-1) under an argon atmosphere. Specimens were etched with two solutions (2.5% HF + 2.5% HNO(3) + 95% H(2)O; 25% HN(4)OH + 30% H(2)O(2) + 45%H(2)O). It was found that the silver-based braze alloy has a eutectic structure. In the diffusion layer between the beta-titanium wire and this silver-based braze alloy, Cu and Ti were enriched on the wire side, and Sn and Ti were enriched on the braze alloy side. The titanium-based braze alloy has a dendritic structure. Beta-titanium wire specimens brazed with the titanium-based braze alloy had a thicker intermediate area compared to the silver alloy; Ti in the diffusion layer had an irregular concentration gradient, and the braze alloy side had higher Ti concentration. The original microstructure of the beta-titanium wire was not altered with the use of either braze alloy. Infrared brazing of beta-titanium orthodontic wire is acceptable for clinical use, since the wire microstructure did not deteriorate with either the titanium-based or silver-based braze alloy. The differing microstructures of the joint regions for the two braze alloys suggest that the joint strengths may also differ.
authors.affiliation: Department of Orthodontics, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido, Japan. iijima@hoku-iryo-u.ac.jp
authors.forename: Masahiro
authors.initials: M
authors.lastname: Iijima
authors.forename: William A
authors.initials: WA
authors.lastname: Brantley
authors.forename: Isao
authors.initials: I
authors.lastname: Kawashima
authors.forename: Naoki
authors.initials: N
authors.lastname: Baba
authors.forename: Satish B
authors.initials: SB
authors.lastname: Alapati
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Yuasa
authors.forename: Hiroki
authors.initials: H
authors.lastname: Ohno
authors.forename: Itaru
authors.initials: I
authors.lastname: Mizoguchi
mesh_terms: D012994:Dental Soldering; D004577:Electron Probe Microanalysis; D007259:Infrared Rays; D008855:Microscopy, Electron, Scanning; D009969:Orthodontic Wires; D014025:Titanium
chemical_list: C023988:beta titanium; D014025:Titanium