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Effect of hot rolling on microstructure and transformation cycling behaviour of equiatomic NiTi shape memory alloy

Ahadi, A ; Sharif University of Technology | 2012

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  1. Type of Document: Article
  2. DOI: 10.1179/1743284711Y.0000000130
  3. Publisher: 2012
  4. Abstract:
  5. In this study, a near equiatomic NiTi shape memory alloy was hot rolled at 800°C using thethickness reductions of 30 and 50%. Optical and transmission electron microscopy, together withX-ray diffraction were used to demonstrate the microstructural changes associated with the hotrolling at different thickness reductions. Repeated transformation cycling was employed toinvestigate the evolution of R phase during cycling. Microstructural observations revealed thepresence of deformation twins embedded in an elongated grain matrix in the hot rolled material.Moreover, it was found that with increasing degree of thickness reduction, the size and number ofdeformation twins increased throughout the grains. After transformation cycling, higher values ofδHA→R were noticed in the 50% hot rolled material in comparison to the annealed condition.Transmission electron microscopy microstructure of the 50% hot rolled material transformationcycled up to 50 cycles showed that R phase packets are frequently observed near grainboundaries. The observation of R phase packets near the grain boundaries in the hot rolledmaterial was attributed to the high stress concentrations at these regions
  6. Keywords:
  7. Deformation twins ; Equiatomic NiTi ; Hot rolling ; R phase packets ; Transmission electron microscopy ; Deformation twin ; Different thickness ; Elongated grains ; High stress concentration ; Hot-rolled ; Microstructural changes ; Microstructural observations ; NiTi shape memory alloys ; R phase ; Thickness reduction ; Deformation ; Grain boundaries ; Microstructure ; Stress concentration ; Shape memory effect
  8. Source: Materials Science and Technology (United Kingdom) ; Volume 28, Issue 6 , 2012 , Pages 727-732 ; 02670836 (ISSN)
  9. URL: http://www.maneyonline.com/doi/abs/10.1179/1743284711Y.0000000130