• Korean Journal of Materials Research
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• v.28 no.7
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• pp.381-390
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• 2018

Shape memory alloys(SMAs) have revolutionized the material engineering sciences as they exhibit exclusive features i.e. shape memory effect(SME) and super-elasticity. SMAs are those alloys that when deform return to their predeformed shape upon heating, they also restore their original shape by removing the load. Research on properties of newly advent of several types of ferrous based shape memory alloys(Fe-SMAs), shows that they have immense potential to be the counterpart of Nitinol(NiTi-SMA). These Fe-SMAs have been used and found to be effective because of their low cost, high cold workability, good weldability & excellent characteristics comparing with Nitinol(high processing cost and low cold workability) SMAs. Some of the Fe-SMAs show super-elasticity. Fe-SMAs, especially Fe-Mn-Si alloys have an immense potential for civil engineering structures because of its unique properties e.g. two-way shape memory effect, super elasticity and shape memory effect as well as due to its low cost, high elastic stiffness and wide transformation hysteresis comparative to Nitinol. Further research is being conducted on SMAs to improve and impinge better attributes by improving the material compositions, quantifying the SMA phase transition temperature etc. In this research pre-existing Fe-SMAs are categorised and collected in a tabulated form. An analysis is performed that which category is mostly available. Last 50 years data of Fe-SMA publications and US Patents is collected to show its importance in terms of increasing research on such type of alloys to invent different compositions and applications. This data is analysed as per different year groups during last 50 years and it was analysed as per whether the keywords exist in title of an article or anywhere in the article. It was found that different keywords related to Fe-SMAs/categories of Fe-SMAs, almost don't exist in the title of articles. However, these keywords related to Fe-SMAs/categories of Fe-SMAs, exist inside the article but still there are not too many publications related to Fe-SMAs/categories of Fe-SMAs.

• The korean journal of orthodontics
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• v.53 no.2
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• pp.89-98
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• 2023

Objective: This study aimed to compare the mechanical and thermal properties in the anterior and posterior segments of new and retrieved specimens of a commercially available multizone superelastic nickel-titanium (NiTi) archwire. Methods: The following groups of 0.016 × 0.022-inch Bioforce NiTi archwires were compared: a) anterior and b) posterior segments of new specimens and c) anterior and d) posterior segments of retrieved specimens. Six specimens were evaluated in each group, by three-point bending and bend and free recovery tests. Bending moduli (Eb) were calculated. Furthermore, the new specimens were evaluated with scanning electron microscopy/energy-dispersive X-ray spectrometry. A multiple linear regression model with a random intercept at the wire level was applied for data analysis. Results: The forces in the posterior segments or new specimens were higher than those recorded in the anterior segments or retrieved specimens, respectively. Accordingly, Eb also varied. Higher austenite start and austenite finish (Af) temperatures were recorded in the anterior segments. No statistically significant differences were found for these temperatures between retrieved and new wires. The mean elemental composition was (weight percentage): Ni, 52.6 ± 0.5; Ti, 47.4 ± 0.5. Conclusions: The existence of multiple force zones was confirmed in new and retrieved Bioforce archwires. The retrieved archwires demonstrated lower forces during the initial stages of deactivation in three-point bending tests, compared with new specimens. The Af temperature of these archwires may lie higher than the regular intraoral temperature. Even at 2 mm deflections, the forces recorded from these archwires may lie beyond biologically safe limits.