Microstructural changes in quasicrystalline Al–Mn–Be–Cu alloy after various heat treatments

Abstract

Microstructural changesinq uasicrystalline Al-Mn-Be-Cua lloy afterv ariousheat treatmentsIn this studyw ei nvestigated the microstructural changes after av ariety of heat treatments of the quasicrystalline Al -Mn-Be-Cu alloy. In addition, we report on Vickers microhardness measurementsa nd tensile-test results for the same materials. The samples werep roduced in ac onventional manner,i .e., melting in an electrical resistance furnacei na ir and ag ravitational casting process usinga round copper die, which was in the form of at ensile-test specimen withadiameterof5mm. After the casting, some of the samples werej ust solution treated (annealed)a nd then quenched in water, while others were additionally aged (artificially -T 6, or naturally -T 4) or directly aged after the casting. In comparison to the as-cast state, the Vickers microhardness values of the aluminum-based matrix and the tensilep roperties of the samples decreased when just the solutiont reatment, T4 or T6 treatment was performed. The tensile properties also decreased after the heat treatments. Amicrostructural inspection revealed that the microstructural changes occurred already duringt he solution treatment, i. e., the formationo ft he phases Be 4 Al(Mn,Cu) and s 1 -Al 29 Mn 6 Cu 4 on the approximant H-Al 4 Mn and quasicrystalline i-phase particles' edges and the occurrence of precipitatesinthe a Al matrix.The precipitates that would additionally contribute to the hardening of the alloyd id not form. The directly aged samples showed little or no increase in microhardness values in comparison to the as-cast samples, but possibilities of h @ precipitates being formed from the already saturated matrix after the casting could not be excluded.After all the heat treatments the quasicrystalline i-phase, as ap rimary and eutectic phase, was preserved.

Ageing of Al-Mn-Cu-Be Alloys for Stimulating Precipitation of Icosahedral Quasicrystals

“…In Al-Mn-Cu alloys, decagonal quasicrystals can form upon solidification [23,40]. The decagonal Al-Mn-Cu phase is closely related to the equilibrium phase τ 1 .…”

Microstructure and Indentation Properties of Single-Roll and Twin-Roll Casting of a Quasicrystal-Forming Al-Mn-Cu-Be Alloy

“…At higher cooling rates, the primary IQC phase can form [11]. At somewhat lower cooling rates also a decagonal quasicrystalline phase (DQC) [13,36] or a quasicrystalline approximant Al 15 Mn 3 Be 2 can form [9,11,13]. The main point is that all three phases IQC, DQC and Al 15 Mn 3 Be 2, consist of icosahedral clusters.…”

“…They found that combined additions of Be and Cu, in particular, were helpful in the formation of quasicrystals during gravitational casting. These alloys can form primary icosahedral quasicrystals (IQC) in a dendritic or polygonal shape, and quasicrystals are also formed during the final stages of solidification Metals 2022, 12, 187 2 of 16 as a binary (α-Al + IQC) eutectic [12,13]. The Al-Mn-Cu-Be alloy is still experimental.…”