Precipitate-induced R-phase in martensitic transformation of as-spun and annealed Ti51Ni49 ribbons

JOURNAL OF ALLOYS AND COMPOUNDS

卷:505

Article

Wu, Ling-Mei¹  Chang, Shih-Hang²  Wu, Shyi-Kaan¹ 

[1] Natl Taiwan Univ, Dept Mat Sci & Engn, Taipei 106, Taiwan

[2] Natl Ilan Univ, Dept Chem & Mat Engn, Ilan 260, Taiwan

关键词: Metals and alloys;    Rapid-solidification;    Phase transitions;    Shape memory;    Transmission electron microscopy TEM;   

DOI  :  10.1016/j.jallcom.2010.06.019

来源: Elsevier

【 摘 要 】

Differential scanning calorimetry (DSC) results indicate that a two-step B2 -> R -> B19' martensitic transformation and a one-step B19' -> B2 transformation exhibit in as-spun and in 200-600 degrees C annealed Ti51Ni49 ribbons. Guinier-Preston (GP) zones and Ti2Ni precipitates are formed in ribbons annealed at <= 300 degrees C and >= 400 degrees C, respectively, and a conspicuous increase of DSC transformation peak temperature occurs in between 300 degrees C and 400 degrees C. The sizes of GP zones and Ti2Ni precipitates increase with increased annealing temperature. Transmission electron microscope (TEM) observations show that GP zones can induce the R-phase and both of them are formed along (1 0 0)(B2) directions. DSC and TEM tests show that Ti2Ni precipitates can induce the R-phase more than GP zones and the induced R-phase plates are also found along (1 0 0)(B2) directions. Experimental results show that the growing direction of R-phase plates is strongly confined by that of GP zones and Ti2Ni precipitates. The length of R-phase plates can reach about 2 mu m in 300 degrees C annealed ribbon. (C) 2010 Elsevier B.V. All rights reserved.

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