The effect of cooling rate on the precipitation of Î³â² in Ni-11.6 at.%Al alloy

A. Samadi,; A. Abdollah-zadeh,; S.H. Razavi,; H. Assadi,

The effect of cooling rate on the precipitation of Î³â² in Ni-11.6 at.%Al alloy

Authors

ahad samadi ¹

A. Abdollah-zadeh ²

S.H. Razavi ¹

H. Assadi ³

¹ Faculty of Materials Engineering, Sahand University of Technology

² Department of Materials Engineering, Tarbiat Modares University, Tehran, Iran

³ Department of Materials and Metallurgical Engineering, Iran University of Science and Technology (IUST), Tehran, Iran

Abstract

The initial stages of the  precipitation in a dilute Ni-Al binary alloy, Ni-11.6 at.%Al, were studied using differential
scanning calorimetry (DSC), X-ray diffraction (XRD), electron diffraction and electron microscopy (FEG-SEM and TEM) techniques. Three samples were similarly solution treated and then cooled to room temperature under different cooling rates, 170، 25 and 0.03oCs-1. The results indicate a clearly homogenous  nucleation during rapid quenching which takes place via simultaneous ordering and phase separation. However, by decreasing the cooling rate to 25oCs-1 the nucleation mechanism changes to heterogeneous on the preferred nucleation sites. The capability of the mentioned empirical techniques for studying the initial stages of the γ′ is another subject which is studied in this article.

Keywords

Ni-Al alloys

γ′ precipitation

Cooling rate

homogenous nucleation

heterogeneous nucleation

FEG-SEM

DSC