Utjecaj brizne hlađenja na mikrostrukturu legure Al94Mn2Be2Cu2

In this study the effect of the cooling rate on the microstructure of Al94Mn2Be2Cu2 alloy was investigated. The vacuum induction melted and cast alloy was exposed to different cooling rates. The slowest cooling rate was achieved by the DSC (10 K•min-1), the moderate cooling rate succeeded by casting in the copper mould (≈1 000 K•s-1) and the rapid solidification was performed by melt spinning (up to 106 K•s-1). The microstructure of the DSC-sample consisted of α-Al matrix, and several intermetallics: τ1-Al29Mn6Cu4, Al4Mn, θ-Al2Cu and Be4Al(Mn,Cu). The microstructures of the alloy at moderate and rapid cooling consisted of the α-Al matrix, i-phase and θ-Al2Cu. Particles of i-phase and θ-Al2Cu were much smaller and more uniformly distributed in melt-spun ribbons.U ovoj je studiji istraživan utjecaj brzine hlađenja na mikrostrukturu legure Al94Mn2Be2Cu2. Legura sintetizirana vakuumskim indukcionim taljenjem i postupkom lijevanja bila je izložena različitim brzinama hlađenja. Najsporije je bilo hlađenje kod DSC (10 K•min-1), umjerene brzine hlađenja prilikom lijevanja u bakreni kalup (≈1 000 K•s-1) a najviše brzine skrućivanja postignute su pomoću metode melt spinning (do 106 K•s-1). Mikrostruktura DSC uzoraka sastoji se od matrice α-Al i nekoliko intermetalnih faza: τ1-Al29Mn6Cu4, Al4Mn, θ-Al2Cu i Be4Al(Mn,Cu). Mikrostruktura legura umjereno i brzo hlađenih sastoji se od matrice α-Al, i-faze i θ-Al2Cu. Čestice i-faze i θ-Al2Cu mnogo su manje i ravnomjerno raspoređene u trakama izrađenima metodom melt spinning

Formation of a quasicrystalline phase in Al–Mn base alloys cast at intermediate cooling rates

Al-rich 94Al–6Mn and 94Al–4Mn–2Fe alloys were suction-cast to evaluate thefeasibility of obtaining bulk quasicrystal-strengthened Al-alloys at intermediatecooling rates alloyed with non-toxic, easily accessible and affordable additions.The influence of different cooling rates on the potential formation of a quasicrystallinephase was examined by means of scanning and transmissionelectron microscopy, X-ray diffraction and differential scanning calorimetry.Increased cooling rates in the thinnest castings entailed a change in samplephase composition. The highest cooling rates turned out to be insufficient toform an icosahedral quasicrystalline phase (I-phase) in the binary alloy. Instead,an orthorhombic approximant phase occurred (L-phase). The addition of Fe tothe 94Al–6Mn binary alloy enhanced the formation of a quasicrystalline phase.At intermediate cooling rates of 102–103 K/s, various metastable phases wereformed, including decagonal and icosahedral quasicrystals and their approximants.Rods (1 mm in diameter) composed of I-phase particles embedded in Almatrix exhibited a hardness of 1.5 GPa, much higher than the 1.1 GPa of 94Al–6Mn

Solidification of Al-Mn-based alloys under various processing parameters

Abstract A number of Al-Mn-based alloys were investigated with a view to their commercialization. Various casting techniques were used to affect the constitution of the alloys studied from crystalline to quasi-crystalline as well as other metastable states. Variations in cooling rates and chemical composition, along with other processing parameters, have been shown to allow us to control the final constitution and properties of what we believe could be the next generation of commercial Al-based alloys. Our research has shown that the solidification process of Al-Mn based alloys with additions of other metallic elements can lead to the formation of very complex final states, opening up possibilities for designing and controlling the properties of alloys. The solidification process in the alloys studied proved to be very complex, but can be explained by basic knowledge of the crystallisation of metallic melts. We have discovered that by changing the processing parameters and the chemical composition of the alloys in a controlled way, it is possible to tailor the final properties of the alloys, making them attractive for commercial purposes.</jats:p