DSC Analysis Of Order–Disorder Transition In Ni3Al Based Alloys From Ni-Al-Cr System

Abstract

DSC analySIS of orDer-DISorDer tranSItIon In ni3al baSeD alloyS from ni-al-Cr SyStemAnAlizA DSC przemiAn typu porząDek-nieporząDek w StopACh nA oSnowie ni3al z ukłADu ni-al-CrNi-Al-Cr system is significant for industrial alloys based on intermetallic phase Ni3Al, that crystallizes in crystal lattice L12. It is indicated as γ′, contrary to disordered phase γ which occurs with addition of chromium. DSC analysis was performed on alloys of chemical composition from Ni75Al25÷Ni75Cr25 range of Ni-rich part of Ni-Al-Cr system. In addition, few measurements were conducted using DTA method. Based on curves registered, it was possible to identify characteristic temperature during heating and cooling of the sample. It corresponds to existence of phase boundary γ′+γ / γ in examined alloys. Results of thermal analysis were compared with results obtained with other method performed by authors which is solution calorimetric method.Keywords: Ni-Al-Cr system, intermetallic phase Ni3Al , order-disorder, DSC analysisUkład Ni-Al-Cr jest ważnym układem dla przemysłowych stopów na osnowie fazy międzymetalicznej Ni3Al, która krystalizuje w uporządkowanej sieci L12. Oznacza się ją jako γ′ w odróżnieniu od fazy nieuporządkowanej γ, która pojawia się wraz z dodatkiem stopowym chromu. Wykonano serię stopów, których skład chemiczny leży na linii Ni75Al25÷Ni75Cr25 w bogatej w nikiel części układu Ni-Al-Cr i poddano je analizie DSC. Dodatkowo wykonano kilka pomiarów metodą DTA. Na podstawie zarejestrowanych krzywych udało się zidentyfikować charakterystyczne temperatury podczas nagrzewania i studzenia próbki. Odpowiadają one miejscom występowania granicy międzyfazowej γ′+γ / γ w stopach. Wyniki analiz termicznych zestawiono z wynikami innej metody zastosowanej przez autorów tj. kalorymetrycznej metody typu rozpuszczania.

Determination of γ′+γ / γ Phase Boundary in Ni-Al-Cr System Using DTA Thermal Analysis

“…Using thermal analysis methods such as DSC and DTA, for alloy research from Ni75Al25÷Ni75Cr25 section enabled identification of course of high-temperature phase boundary γ′+γ / γ. At the same time, agreement of results obtained with calorimetric solution method was met [16]. Mechanical properties at elevated temperature, in modern alloys based on intermetallic phase Ni3Al are connected with phase composition, especially with proportion of ordered phase γ′ (L12) and disordered phase γ (A1).…”

“…Difficulty in determination of temperature of 2O-OD transition in residual alloys and during heating of alloys Ni79,8Al15,1Cr5,1 and Ni80,6Al13,2Cr6,2 is a result of low sensitivity of DTA method related to measuring apparatus design. Authors noted this problem during research of alloys from Ni75Al25÷Ni75Cr25 section, where using DSC method enabled to observe more distinct effects of 2O-OD transition [16]. (Fig.…”

“…In previous work, authors stated lack of clear influence of heating and cooling rate on transition temperature orderdisorder in alloys from Ni75Al25÷Ni75Cr25 section [16]. Based on that and in order to compare results within the scope of the same Ni-Al-Cr system, in this work all measurements were determined with rate 20°C/min.…”

Thermal and structural analysis of high-tin bronze of chemical composition corresponding to the composition of the singing bowl

“…As it is commented by the author of [16], it indicates the presence of a second-order transition between β and γ. Additional confirmation for this assumption can be the presence of thermal effect occuring also during cooling (570°C) that shows good compatibility with order-disorder transition observed in alloys from Ni-Al-Cr or Fe-Al systems [17][18][19][20].…”

“…This behavior results from features of the DTA method, especially related to the heat transfer rate between sample and crucible and between crucible and thermocouple. Large differences indicate that studied alloy shows a tendency to turn into non-equilibrium state during rapid cooling [17,18].…”