Microstructure and impression creep characteristics Al-9Si-xCu aluminum alloys

Abstract

The effects of 1.5, 2.5 and 3.5 wt.% Cu additions on the microstructure and creep behavior of the as-cast Al-9Si alloy were investigated by impression tests. The tests were performed at temperature ranging from 493 to 553 K and under punching stresses in the range 300 to 414 MPa for dwell times up to 3000 seconds. The results showed that, for all loads and temperatures, the Al-9Si-3.5Cu alloy had the lowest creep rates and thus, the highest creep resistance among all materials tested. This is attributed to the formation of hard intermetallic compound of Al 2 Cu, and higher amount of α-Al 2 Cu eutectic phase. The stress exponent and activation energy are in the ranges of 5.2-7.2 and 115 -150 kJ/ mol, respectively for all alloys. According to the stress exponent and creep activation energies, the lattice and pipe diffusion-climb controlled dislocation creep were the dominant creep mechanism.

High-Temperature Behavior of High-Pressure Diecast Alloys Based on the Al-Si-Cu System: The Role Played by Chemical Composition

“…During the manufacturing process of the investigated materials, the solidification stage was followed by fast cooling up to the extraction of the thin HPDC specimens from the die, followed by slower air cooling to room temperature. According to literature [9], the cooling stage does not significantly alter the amount of phases.…”

“…While many experimental studies have been devoted to the thermal stability of Al-Si-Cu casting alloys and to their direct effects on hardness and room-temperature mechanical properties [7,8], less attention has been paid to the temperature dependence of stress-strain curves and the tensile properties in a wide temperature range [8]. Small efforts have also been dedicated to describe the effects of microstructural stability on the mechanical properties after long-term exposure to elevated temperatures, for instance by means of long-term experimental creep tests [9] or tensile testing in a wide range of strain rates [8].…”