Role of Er₂O₃ Reinforcement and Milling Duration in Tailoring the Performance of A201 Aluminum Alloy

Abstract

Aluminum alloys, particularly the A201 grade in the Al Cu family, are widely used in aerospace
and defense applications due to their high specific strength and stable mechanical performance at high
temperatures. Enriching these alloys with ceramic reinforcements has recently attracted significant attention
because it can further enhance strength, hardness, and thermal stability. This study systematically
investigated the effects of milling time on the microstructure and mechanical properties of A201 aluminum
alloy reinforced with 1 wt% Er₂O₃. A201.0 alloy chips and Er₂O₃ powder were mechanically milled using
a planetary ball mill for 1, 2, and 4 hours, followed by hot pressing at 500°C under 180 MPa for 10 minutes
to produce samples. Microstructural observations revealed that 1 hour of milling resulted in limited
interaction between the matrix and reinforcement, resulting in partial agglomeration and relatively higher
porosity. 2 hour milling produced flake like particles that trapped additional pores and negatively impacted
densification. However, 4 hour milling resulted in improved particle refinement, increased Er₂O₃
distribution, and decreased porosity, resulting in a more homogeneous and compact structure.
Consequently, density values increased from 2.42 g/cm³ (1 hour) to 2.67 g/cm³ (4 hours). Hardness
measurements followed a similar trend, increasing from 85 HB to 99 HB; the slight decrease at 2 hours was
attributed to increased pore concentration. Overall, the findings indicate that milling time plays a decisive
role in determining the structural integrity and mechanical performance of Er₂O₃ reinforced A201
composites. Among the parameters examined, the 4 hour milling time provided the optimal balance
between densification, hardness, and microstructural homogeneity.