Abstracts Book - IMRC 2018

• SD7-P010
INFLUENCE OF MG ADDITIONS, HOT-EXTRUSION AND COLD-
ROLLING IN AGED 2024 ALLOY
Lilia Jasiel García Hernández 1 , Carlos Gamaliel Garay Reyes 1 , Aisse Hernández Arrollo 2 ,
Ivanovich Estrada 1 , Hansel Manuel Medrano Prieto 1 , Maria Cristina Maldonado Orozco 2 ,
Roberto Martinez Sanchez 1
1 Centro de Investigación en Materiales Avanzados, S.C., Metalurgia e Integridad Estructural,
Mexico. 2 Universidad Autónoma de Chihuahua, Facultad de Ingeniería, Mexico.
Al-2024 alloys with high specific strength, good fracture toughness, and
excellent fatigue properties have found important applications in the aerospace
industry. In commercial 2024 alloys, Cu and Mg are the main alloying elements
with small amount of Si and other minor elements such as Mn, Zn, Ti and Fe.
Nonetheless, recently has been reported an increment on strength and
hardness by increasing the Mg content (< 2 wt.%); however, this improvement
of mechanical properties is accompanied by a decrease in ductility and impact
resistance. The 2024 alloy with Mg additions (0.25 wt.%) was made by
conventional casting, the melt was degassed with argon gas for 5 min period
and AlTiB was added as grain refiner. Modification with Mg was performed with
addition of pure Mg (99.95%). The hot-extrusion consisted of a thickness
reduction in the samples (10 mm in diameter) by using indirect extrusion and
an extrusion ratio of 16 at 480°C. The solution heat treatment was at 495°C for
7h. The cold-rolling involved 5 to 15% thickness reductions; and a final aging step
(195°C) at several times was realized. The microstructural characterization was
done by XRD, SEM and TEM. The mechanical properties were evaluated by
Vickers hardness. The results show that the microstructure changed of dendritic
grains in as-cast condition to equiaxed grains after hot-extrusion. The spatial
distribution of Cu-rich phases becomes more homogeneous and smaller
particles are observed. In addition, after solution heat treatment dissolution of
Cu-rich phases was carried-out. The samples after cold-rolling 15% present two
peaks-hardening, the first peak is associated to dynamic precipitation and a
second peak at 600 min aging associated to Al 2 Cu and Al 2 CuMg precipitates. It is
concluded that the hot-extrusion and cold-rolling generate microstructural
changes that improve the hardness of 2024 alloy and a double hardening peak
during aging process.
Keywords: 2024 alloy, Cold rolling, Mg addition
Presenting authors email: roberto.martinez@cimav.edu.mx