Effect of Si on Fe-rich intermetallic formation and mechanical properties of heat-treated Al–Cu–Mn–Fe alloys

Abstract

The effect of Si on Fe-rich intermetallics formation and mechanical properties of heat-treated squeeze cast Al-5.0Cu-0.6Mn-0.7Fe alloy was investigated.Our results show that increasing Si content promotes the formation of Al15(FeMn)3(SiCu)2 (α-Fe), and varying the morphology of T (Al20Cu3Mn2) where the size decreases and the amount increases. The major reason is that Si promotes heterogeneous nucleation of the intermetallics leading to finer precipitates. Si addition significantly enhances ultimate tensile strength and yield strength of the alloys. The strengthening effect is mainly owing to the dispersoid strengthening by increasing volume fraction of T phase and less harmful α-Fe with a compact structure, which make the cracks more difficult to initiate and propagation during tensile test. The squeeze cast Al-5.0Cu-0.6Mn-0.7Fe alloy with 1.1% Si shows significantly improved mechanical properties than the alloy without Si addition, which has tensile strength of 386 MPa, yield strength of 280 MPa and elongation of 8.6%.

Effect of Compound Fields of Ultrasonic Vibration and Applied Pressure on the 3D Microstructure and Tensile Properties of Recycled Al-Cu-Mn-Fe-Si Alloys

“…Thus, the white phase is identified as α(CuFe) (Al 7 Cu 2 Fe), and the skeleton-like grey phase is determined as α-Fe (Al 15 (FeMn) 3 (SiCu) 2 ). The results are in good agreement with the literature [6].…”

“…Si exists in the alloy in two different states: Dissolve in the α-Al matrix and precipitated as Si-containing intermetallic phases [2]. According to the present authors [6], Si addition changes the plate-like β-Al 7 Cu 2 Fe and Al 3 (FeMn) to Chinese-script Al 6 (FeMn), and Al 15 (FeMn) 3 (SiCu) 2 (α-Fe) and accelerates the aging kinetics of precipitates after heat treatment. In the meantime, Mn addition promotes the formation of Chinese-script Fe-rich phases [7].…”

3D characterization of ultrasonic melt processing on the microstructural refinement of Al Cu alloys using synchrotron X-ray tomography

“…As shown in Fig. 6a, the 3D morphology plate-like β-Al7Cu2Fe shows "hollow" characteristics, owing to the coupled eutectic reaction with α-Al: L → α-Al + α-Al15(FeMn)3Cu2 + β-Al7Cu2Fe + Al2Cu [6,23] at 542-537 ºC. After USP, 3D morphology of β-Al7Cu2Fe become much thinner (Fig.…”

“…With the accumulation of iron could be resulting in the formation of hard and brittle Fe-rich intermetallic phases (named Fe-rich phases hereafter), especially the plate-like β-Al5FeSi and β-Al7Cu2Fe, which have the detrimental effect on the castability and mechanical properties [4]. Thus, the authors [5,6] have been carried out to modify the morphology of Ferich intermetallic phase from plate-like to less-harmful Chinese script through addition the neutralize element, i.e., Mn and Si. However, additions of neutralizing elements increase the volume fraction of Fe-rich intermetallic phases and decrease the toughness of the alloys.…”

Synchrotron X-ray tomography investigation of 3D morphologies of intermetallic phases and pores and their effect on the mechanical properties of cast Al-Cu alloys

“…Understanding the fundamental relationship between the 3D structures of different phases and their related properties is important for developing new materials. At present, the characterization of different phases is mainly conducted in two dimensions (2D) using optical or electron microscopy [6][7]. However, these techniques are insufficient to fully reveal the complicated three-dimensional (3D) morphologies and spatial structure of intermetallic phases.…”