کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
10714309 1025585 2011 10 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Thermodynamics of α″→β phase transformation and heat capacity measurements in Ti-15 at% Nb alloy
موضوعات مرتبط
مهندسی و علوم پایه فیزیک و نجوم فیزیک ماده چگال
پیش نمایش صفحه اول مقاله
Thermodynamics of α″→β phase transformation and heat capacity measurements in Ti-15 at% Nb alloy
چکیده انگلیسی
The phase stability of Ti-15 at% Nb alloy has been studied in the temperature range 466-1258 K using inverse drop calorimetry. In the annealed condition, the alloy consists of orthorhombic α″-martensite and bcc β phases. The calorimetry experiments indicated the occurrence of two phase changes upon heating. They are (i) precipitation of hexagonal ω phase at 582±2 K followed by (ii) α″→β in the temperature domain 836-985±2 K. The enthalpy change due to ω formation is small; however, the α″→β phase transformation is associated with a measurable enthalpy effect of 57±3 J g−1. Since α″→β phase change occurs over a temperature interval, the measured enthalpy in the transformation domain derives from two principal contributions, namely, the matrix contribution coming from untransformed α″-martensite and β phase mix and another transformational component arising from continuous α″→β phase change. Since the fractional extent of α″→β transformation varies continuously with temperature the transformation enthalpy also exhibits similar temperature dependence. This aspect is modeled using Kolmogorov-Johnson-Mehl-Avrami formalism for treating the diffusional transformation kinetics. Further, the measured enthalpy variation with temperature has been subjected to standard analytical treatment to obtain a comprehensive thermodynamic description of entire α″+β region.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Physica B: Condensed Matter - Volume 406, Issue 22, 15 November 2011, Pages 4200-4209
نویسندگان
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