Development of an Al–Mn–Be–Cu alloy with improved quasicrystalline forming ability

Abstract

An Al94Mn2Be2Cu2 cast alloy was developed displaying increased quasicrystalline formation ability at moderate cooling rates. The as-cast microstructure consisted of a mainly icosahedral phase in the Al-matrix. The microstructure remained stable during uniform heating to 580 °C and isothermal annealing at 400 °C. Most of the icosahedral phase was preserved even after 24 h annealing at 500 °C. For that reason, this alloy presents a promising basis for further development of cast Al-alloys containing quasicrystals.

Microindentation of dispersed phases in an Al94Mn2Be2Cu2 alloy

“…Both quasicrystals and quasicrystalline approximants consist of well-defined clusters, most often of icosahedral symmetry, and belong to a class of so-called complex metallic alloys [14]. In one of the recently developed alloys, an Al 94 Mn 2 Be 2 Cu 2 alloy [15], both an i-phase and a quasicrystalline approximant can be found. This offers a nice possibility of making comparison between the mechanical properties of these two phases, having very similar compositions and cluster arrangements.…”

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

“…Reference [2] further observesthe preservation of the iphase after a2 4hour-long annealing at 500 8 C. Even after au niform heating up to 580 8 Ca nd at ac ooling rate of 10 K·min -1 ,n ol arge microstructural changes wereo bserved.…”

“…About half of the QCs in metallic systemsa re metastable, which means rapid-solidification techniques (e. g.,melt-spinning) are required fortheir formation, as shownbySteurer and Deloudia [6]. Forour study, an alloy similar to Al-2Mn-2Be2Cu (at.%) was chosen because of its known tendency for QC (i-phase) formation at moderate cooling rates [5,[7][8][9][10][11][12][13][14][15][16][17][18]. Moreover, copper can be added to the alloy, since it has agood solubility in aluminum, and an umber of research papers, for example [8 -12], have suggested that copper increases the nucleationo ft he QCs and stabilizes the QC i-phase.…”

“…It is possible to find data on already-performed heat treatments of Al -Mn-Be-Cu alloys in Refs. [2] the 1hour annealing of an Al-2Mn-2Be-2Cu (at.%) alloy at 400 and 580 8 Ci sp resented.T he alloyw as exposed to heating and cooling with arate of 10 K·min -1 . The authors of Ref.…”

“…The authors of Ref. [2,11,12], where the alloys were cast in ar ectangular copper mold (100 mm · 10 mm · 1mm) and witha na lloy composition of Al-2Mn-2Be-2Cu (at.%),o rs imilar. The annealing was performed at 300, 400 and 500 8 C. Annealing at 300 and 400 8 Clasted for1hour, while the annealing at 500 8 Clasted from 30 min to 7days.…”