Annealing behaviour of nanocrystalline NiTi (50 at% Ni) alloy produced by high-pressure torsion

R. Singh*, H. Rösner, E. A. Prokofyev, R. Z. Valiev, S. V. Divinski, G. Wilde

*المؤلف المقابل لهذا العمل

نتاج البحث: المساهمة في مجلةArticleمراجعة النظراء

9 اقتباسات (Scopus)


An equiatomic nanocrystalline NiTi alloy, deformed by high-pressure torsion (HPT), was investigated. The as-prepared bulk NiTi alloy consisted of both amorphous and nanocrystalline phases. Crystallization and structural changes during annealing were investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and transmission electron microscopy (TEM). DSC thermograms and X-ray analyses revealed stress relaxation and partial crystallization below 500 K, while grain growth of the nanocrystals occurred predominantly after heating to temperatures above 573 K. Along with the amorphous phase crystallization, a continuous growth of pre-existing nanocrystals that are retained after HPT was observed. The DSC signals observed during continuous heating experiments indicate an unusually large separation between the crystallization and growth stages. A detailed analysis of the evolution of the enthalpy release upon annealing revealed reproducibly non-monotonous trends with annealing temperature that cannot be explained solely by nucleation and growth of crystalline volume fractions. Instead, the results can be rationalized by assuming a reverse amorphization process occuring during annealing at 523 K. This behavior, which also caused a large variation in nanocrystal size after annealing at higher temperatures, is discussed with respect to the nanoscale microstructural heterogeneity after initial deformation processing.

اللغة الأصليةEnglish
الصفحات (من إلى)3079-3092
عدد الصفحات14
دوريةPhilosophical Magazine
مستوى الصوت91
رقم الإصدار22
المعرِّفات الرقمية للأشياء
حالة النشرPublished - أغسطس 1 2011

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