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MATERIALS SCIENCE
ArticleName Effect of hafnium transition metal additives on the microstructure of 01570 aluminum alloy
DOI 10.17580/tsm.2020.11.12
ArticleAuthor Yashin V. V., Aryshensky E. V., Drits A. M., Latushkin I. A.
ArticleAuthorData

JSC Arconic SMZ, Samara, Russia:

V. V. Yashin, Manager, e-mail: Vasiliy.Yashin@arconic.com
I. A. Latushkin, Leading Specialist, e-mail: Ilya.Latushkin@arconic.com

Samara National Research University, Samara, Russia:

E. V. Aryshensky, Associate Professor of the Chair for Metal Technology and Aviation Materials Science2, Candidate of Technical Sciences, e-mail: ar-evgenii@yandex.ru

 

JSC Arconic SMZ, Moscow, Russia:

A. M. Drits, Director for Business Development and New Technologies, Candidate of Technical Sciences, e-mail: Alexander.Drits@arconic.com

Abstract

The study addresses the effect of hafnium on microstructure, mechanical properties and stability of Al3Sc type strengthening particles in Al – Mg system 01570 alloy with scandium and zirconium additions. As part of the study, 01570 alloy-based ingots with hafnium content of 0.1% and 0.2% (here and everywhere hereinafter % weight is indicated) were cast in steel chill molds with zirconium and without zirconium addition. The obtained ingots grains size was examined using optical microscope. It was established, that 0.2% Hf addition to the previously designed 01570 alloy can reduce the average nominal grain diameter by half. A number of anneals was performed at temperatures of 400 oC and 450 oC with 1, 10, 30 minutes, 1, 4, 8, 16, 32 and 56 hours soaking times, to study the rate of supersaturated solid solution decomposition and determine the moment of strengthening dispersed particles coalescence onset. Annealed samples were measured for microhardness, electrical resistance and examined using scanning electron microscopy. It was demonstrated, that samples with hafnium do not lose strengthening phase stability at traditional treatment temperature of 400 oC with considerable soaking time (up to 56 h), at 450 oC decrease in microhardness is observed only after 4 hours of soaking. The samples were pressure-formed, i.e., hot and cold rolled, to determine recrystallization onset, it was established, that even at 500 oC and short soaking period (up to 30 minutes) rolled samples with hafnium still have some not recrystallized microstructure, while the samples without hafnium have visible equiaxed recrystallized grains. Using transmission electron microscope, it was possible to establish that the dispersed particles obtained in the alloy with 0.2% Hf retain a size of about 9 nm after the treatment cycle, and the average distance between them is 62 nm.
The study was supported by a grant from the Russian Science Foundation, project 18-79-10099.

keywords Aluminum alloys, hafnium alloying, microstructure, microhardness, electrical resistance, recrystallization, dispersed particles, particles coalescence, strengthening particles of Al3TM type
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