Quasicrystalline and L12 precipitates in a microalloyed Al-Mn-Cu alloy

The investigated alloy contained 3.17wt% Mn, 3.08wt% Cu, 0.35wt% Be, 0.21wt.%Sc and 0.14wt.% Zr as determined using AES-ICP (Atomic Emission Spectroscopy – Inductively Coupled Plasma). The alloy was vacuum induction melted using commercially available Al99.8, AlMn10, AlCu25, AlBe5.5, AlSc2 and AlZr10. The alloy was cast into cylindrical copper moulds with the lengths of 40 mm, and the diameters of 4, 6 and 10 mm.

The ageing conditions 1 h at 400 °C were selected after several preliminary trials. The basic metallographic analysis was done by light microscopy (Nikon, Epiphot 300), and scanning electron microscopy (FEI, Sirion 400 NC) equipped with an energy dispersive spectrometer (Oxford Analytical). The phase analysis was carried out by XRD (X-Ray Diffraction) using synchrotron X-rays with a wavelength of 0.0999996 nm (Sincrotrone Elettra, Trieste, Italy).

Lamellas for the transmission electron microscopy (TEM) were prepared using a focused ion beam FIB (FEI, Helios). High-resolution TEM (HRTEM) and energy-dispersive X-ray spectroscopy (EDXS) were carried out in a FEI Titan³ G2 60–300 image corrected electron microscope. The differential thermal analysis was done in Netzsch, STA 449 F3 Jupiter.

The compression and accelerated creep tests at 300 °C and 350 °C were carried out by a quenching dilatometer DIL 805A/D (TA Instruments).