Citation: Zedan, Y.; Garza-Elizondo,
G.H.; Tash, M.; Samuel, A.M.; Doty,
H.W.; Songmene,V.; Samuel, F.H.
Effect of Intermetallics and Drill
Materials on the Machinability of
Al-Si Cast Alloys. Materials 2022, 15,
916. https://doi.org/10.3390/
ma15030916
Academic Editor: Antonio Riveiro
Received: 6 January 2022
Accepted: 21 January 2022
Published: 25 January 2022
Publisher’s Note: MDPI stays neutral
with regard to jurisdictional claims in
published maps and institutional affil-
iations.
Copyright: © 2022 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
materials
Article
Effect of Intermetallics and Drill Materials on the Machinability
of Al-Si Cast Alloys
Yasser Zedan
1
, Guillermo H. Garza-Elizondo
2
, Mahmoud Tash
3
, Agnes M. Samuel
1,
*, Herbert W. Doty
4
,
Victor Songmene
1
and Fawzy Hosny Samuel
2
1
École de Technologie Supérieure, Département de Génie Mécanique, Montréal, QC H3C 1K3, Canada;
yasser.zedan@etsmtl.ca (Y.Z.); victor.songmene@etsmtl.ca (V.S.)
2
Département des Sciences Appliquées, Université du Québec à Chicoutimi, Chicoutimi, QC G7H 2B1,
Canada; memogarzae@gmail.com (G.H.G.-E.); fawzy-hosny.samuel@etsmtl.ca (F.H.S.)
3
Department of Metallurgical Engineering Program, Cairo University, Cairo 12613, Egypt;
mahmoud_tash1@yahoo.com
4
General Motors Global Technology Center, Warren, MI 48093-2350, USA; herb.doty@gm.com
* Correspondence: Agnes-Marie.Samuel@etsmtl.ca
Abstract: The present study was conducted on the machinability of 396 alloy (containing approxi-
mately 11% Si) and B319.2 alloy mainly to emphasize the effects of Fe-intermetallics, i.e., α-Fe, β-Fe,
and sludge. The results demonstrate that the presence of sludge in the form of hard spots has a
significant effect on cutting forces and tool life, in that it decreases drill life by 50% compared to the
base alloy. The formation of the α-Fe phase in the M1 base alloy has a beneficial effect on tool life
in that this alloy produces the highest number of holes drilled compared to alloys containing sludge
or β-Fe; this result may be explained by the fact that the formation of the α-Fe intermetallic, with its
rounded Chinese script morphology and its presence within α-Al dendrites, is expected to improve
matrix homogeneity via hardening of the soft α-Al dendrites. Increasing the Fe-content from 0.5% to
1% in the 396-T6 alloy containing 0.5% Mn produces a distinct improvement in alloy machinability in
terms of cutting force and tool life. The addition of Fe and/or Mn appears to have no discernible
effect on the build-up edge area (BUE) and chip shape.
Keywords: drilling; cutting forces; cutting moments; intermetallics; free cutting elements; tool life
1. Introduction
The 319 and 396 cast aluminum alloys are typically used for the production of aircraft
pump parts, automotive transmission cases, aircraft fittings and controls, water-cooled
cylinder blocks, and numerous other applications. Improvements to these alloys in terms of
their mechanical properties are carried out through melt treatments such as grain refining
and modification. Liquid aluminum is capable of dissolving iron from unprotected steel
tools and furnace equipment. Iron levels can reach 2 wt% at a normal melt temperature
of ~700
◦
C; it should be noted that an Al-Fe eutectic exists at 1.7% Fe at 655
◦
C, as shown
in Figure 1a[1], whereas Figure 1b shows the iron intermetallic phases in the Al corner
of the Al-Si-Fe system [2]. The negative effects of iron in aluminum-silicon alloys can be
minimized or overcome by applying any of the following techniques [3]:
• rapid solidification,
• addition of neutralizing elements such as Mn, Cr, Be, and Ca,
• melt superheating,
• strontium modification, and
• non-equilibrium solution heat treatment.
Materials 2022, 15, 916. https://doi.org/10.3390/ma15030916 https://www.mdpi.com/journal/materials