Effect of annealing on cold-rolled Ni–Ti alloys

✍ Scribed by Arvind K. Srivastava; Zhiqing Yang; Dominique Schryvers; Jan Van Humbeeck

• Publisher: Elsevier Science
• Year: 2008
• Tongue: English
• Weight: 617 KB
• Volume: 481-482
• Category: Article
• ISSN: 0921-5093
• DOI: 10.1016/j.msea.2006.12.216

✦ Synopsis

In this paper, we present a study on the effect of annealing a cold-rolled near-equi-atomic Ni-Ti alloy strip by transmission electron microscopy. Transmission electron microscopy of the as-received sample shows the presence of alternating amorphous and crystalline bands. The crystalline bands have widths of the order of a few microns and contain B2 nanograins of around 20 nm diameter, which are preferentially oriented along the [1,-1,-1] direction, normal to the rolling direction. As-received samples were annealed for 30 min at different temperatures up to 800 • C. With the increase in annealing temperature, crystallization starts in the amorphous bands at around 350 • C and finally ends up with the coarsening of the grains in the entire sample. The annealing of the samples at 450 • C entirely transforms the amorphous bands to crystalline bands and as off 600 • C Ni 3 Ti 2 precipitates are formed. At 800 • C the grain size increases to 30-50 m. Diffraction patterns from such grains reveal the presence of diffuse intensity around reciprocal lattice positions 1/3 1 1 0 * indicating the formation of the R-phase.