On the high temperature coarsening kinetics of gamma ` precipitates in a high strength Co37.6Ni35.4Al9.9Mo4.9Cr5.9Ta2.8Ti3.5 fcc-based high entropy alloy

Pandey, Prafull and Kashyap, Sanjay and Palanisamy, Dhanalakshmi and Sharma, Amit and Chattopadhyay, Kamanio (2019) On the high temperature coarsening kinetics of gamma ` precipitates in a high strength Co37.6Ni35.4Al9.9Mo4.9Cr5.9Ta2.8Ti3.5 fcc-based high entropy alloy. In: ACTA MATERIALIA, 177 . pp. 82-95.

	PDF act_mat_177_82_2019.pdf - Published Version Restricted to Registered users only Download (4MB) | Request a copy
	Microsoft Word 1-s2.0-S1359645419304410-mmc1.doc - Published Supplemental Material Download (3MB)

Abstract

The paper reports evolution of two-phase microstructure quantitatively in a high entropy alloy of composition Co37.6Ni35.4Al9.9Mo4.9Ta2.8Ti3.5. A very high-volume fraction of ordered L1(2) precipitates forms below its solvus temperature of 1156 degrees C that cannot be suppressed during quenching. The quench microstructure contains nanometric bimodal size distribution of spheroidal and irregular precipitates, both having L1(2) ordering (gamma') and a Co + Ni concentration close to 75 at. %, thus representing a stoichiometry of (Ni,Co)(3) (AI,Cr,Ta,Ti,Mo). The alloy shows hardening on aging with a peak in hardness value at 900 degrees C for 50 h of annealing. The morphology of the precipitates at this stage evolves into cuboidal shape having rounded corners with a lattice mismatch of +0.22% with the matrix. A detailed study of the coarsening behaviour of these precipitates in the matrix of complex solid solution indicates that the coarsening follows a modified LSW mechanism with estimated activation energy of 360 +/- 50 kJ/mol between 900 and 1000 degrees C. This is slightly higher than the activation energy of most of the solutes in gamma Co matrix that does not contain heavy elements like W or Re. The high-volume fraction of the precipitates together with coarsening resistance lead to an attractive high temperature strength that is higher than many of the known superalloys.

Item Type:	Journal Article
Publication:	ACTA MATERIALIA
Publisher:	PERGAMON-ELSEVIER SCIENCE LTD
Additional Information:	Copyright of this article belongs to PERGAMON-ELSEVIER SCIENCE LTD
Keywords:	High entropy alloy; gamma precipitates; Coarsening kinetics; High temperature strength; Strengthening mechanism
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	30 Dec 2019 05:54
Last Modified:	30 Dec 2019 05:54
URI:	http://eprints.iisc.ac.in/id/eprint/63577

Actions (login required)

View Item