Nanostructured surfaces
Surface hardening of 2024 aluminum alloy and Cu39Zn1Pb brass with eutectic Al-Cu/C ball milled powder by high-frequency impact treatment
M.O. Vasylyev1, Ya.I. Matvienko1, A.D. Rud1, O.Yu. Khyzhun2, O.M. Fesenko3, A.D. Yaremkevich3
1 G. V. Kurdyumov Institute for Metal Physics of the NAS of Ukraine. Vernadsky blvd., 36, Kyiv-03142, Ukraine.
E-mail: yana_matv@ukr.net
2 Institute for Problems in Materials Science of the NAS of Ukraine. Krzhizhanovsky str., 3, Kyiv-03142, Ukraine.
3 Institute of Physics of the NAS of Ukraine. Nauki Ave., 46, Kyiv-03028, Ukraine.

High-frequency impact treatment (HFIT) is an efficient method of surface hardening and coatings formation among surface severe plastic deformation methods [1]. Due to the formation of stable Al2Cu and metastable disordered Al4Cu9 intermetallic phases, as well as graphite amorphization after high-energy ball milling of the mixture of elemental powders Al and Cu with 5 wt.% of graphite [2], eutectic Al-Cu/C powders can be used as a reinforcement for alloys.
In this work the hardening process of the surface layers of 2024 aluminum alloy caused by microstructure modification and reinforcing effect of Al-31 wt.% Cu/5 wt.% C (Al74Cu14C12 at.%) milled for 8 hours powder introduced by HFIT in various environment was studied. Moreover, HFIT in the air without and with the same powder on the surface hardening of Cu39Zn1Pb brass was also examined.
HFIT of both the samples for 50 seconds resulted in the microhardness increase in 3-3.5 times, compared to the initial state. Thus, HFIT of 2024 aluminum alloy in an inert environment led to microhardness value 4.4 GPa, while the same samples after the treatment in the air performed 7.7 GPa. At that time, Cu39Zn1Pb brass in after HFIT in the air without and with the powder also showed microhardness increase up to 3.3 and 6.3 GPa. Possible strengthening mechanisms are discussed.

1.	М. A. Vasylyev et al. Peculiarities of Structural-Phase State of Surface Layers of Cu39Zn1Pb Brass after High-Frequency Impact Treatment in Different Environment. // Metallofiz. Noveishie Tekhnol.-2020.-42, N. 6.-P.781-796 (in Ukrainian)
2.	Matvienko Y. et al.. Effect of graphite additives on solid-state reactions in eutectic Al-Cu powder mixtures during high-energy ball milling. // Appl. Nanosci.-2020.-10.-P.2803-2811.