Original scientific paper

The Solidification Path of the Complex Metallic Al-Mn-Be Alloy

Boštjan Markoli orcid.org/0000-0003-1217-5505 ; Naravoslovnotehniška fakulteta, Univerza v Ljubljani, Aškerčeva 12, 1000 Ljubljana, Slovenija
Tonica Bončina ; Fakulteta za strojništvo, Univerza v Mariboru, Smetanova 17, 2000 Maribor, Slovenija
Franc Zupanič orcid.org/0000-0002-9402-2854 ; Fakulteta za strojništvo, Univerza v Mariboru, Smetanova 17, 2000 Maribor, Slovenija

Abstract

The solidification paths of the Al_86.1Mn_2.5Be_11.4 and Al₈₄Mn_5.1Be_10.9 alloys, melt spun, cast into a copper mould and controlled cooled (during DSC) were investigated by means of light-optical microscopy (LOM), differential scanning calorimetry (DSC) combined with thermogravimetry (TG) or simultaneous thermal analysis (STA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Auger electron spectroscopy (AES) and the X-ray diffraction (XRD) line in Elletra Trieste, Italy. The constitutions of samples from both alloys were examined in all three states, i.e., after melt spinning, after casting into a copper mould and after differential scanning calorimetry. It was established that in the cast and controlled-cooled specimens the alloys consisted of an aluminium-rich α_Al-matrix, and the Al₄Mn and Be₄AlMn phases. In the case of casting and DSC the primary crystallization began with the precipitation of the Be₄AlMn phase, followed by what can most likely be characterized as a uni-variant binary eutectic reaction L → (Be₄AlMn + Al₄Mn). The solidification process continued with an invariant ternary eutectic reaction, where the remaining melt (L) formed the heterogeneous structure (α_Al + Al₄Mn + Be₄AlMn) or a ternary eutectic. When extremely high cooling rates were employed, as is the case with melt-spinning, the constituting phases of both alloys were precipitated in a very small form and the Be₄AlMn phase was completely absent in the form of primary polygonal particles and replaced by the icosahedral quasicrystalline phase or the i-phase. There was also no evidence of the Al₄Mn phase. The distribution, size and shape of all the constituents in the melt-spun alloys also varied from the contact surface towards the free surface of the ribbons. The smallest constituents were established at the contact surface, measuring less than 0.1 μm, to 0.5 μm at the free surface. The grains of the aluminium-rich matrix had mean diameters of less than 20 μm, close to the free surface, down to 1 μm at the contact surface.

Keywords

complex Al-Mn-Be alloys; metallography; solidification

Hrčak ID:

52234

URI

https://hrcak.srce.hr/52234

Publication date:

30.4.2010.

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