Boštjan Markoli (Author), Tonica Bončina (Author), Franc Zupanič (Author)

Abstract

The solidification paths of the Al86.1Mn2.5Be11.4 and Al84Mn5.1Be10.9 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 samplesfrom 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 ▫$\alpha$▫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 (▫$\alpha$▫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 ▫$\mu$▫m, to 0.5 ▫$\mu$▫m at the free surface. The grains of the aluminium-rich matrix had mean diameters of less than 20 ▫$\mu$▫m, close to the freesurface, down to 1 m at the contact surface.

Keywords

kompleksne Al-Mn-Be zlitine;metalografija;complex Al-Mn-Be alloys;metallography;solidification;

Data

Language: English
Year of publishing:
Typology: 1.08 - Published Scientific Conference Contribution
Organization: UM FS - Faculty of Mechanical Engineering
UDC: 669:620.1
COBISS: 14099478 Link will open in a new window
ISSN: 0011-1643
Views: 1588
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Other data

Secondary title: Način skrućivanja kompleksne metalne Al-Mn-Be legure
Secondary abstract: Načini skrućivanja Al86.1B2.5 Be11.4 i Al84Mn5.1Be10.9 legura dobivenih lijevanjem pri velikim brzinama hlađenja ("melt-spinning" metoda), u bakrenu kokilu i uz kontrolirano hlađenje (za vrijeme DSC) istraživani su metodama optičke mikroskopije (LOM), diferencijalno pretražne kalorimetrije (DSC) u kombinaciji s termogravimetrijom (TG) ili simultanom toplinskom analizom (STA), pretražne elektronske mikroskopije (SEM), transmisijske elektronske mikroskopije (TEM), spektroskopije Augerovih elektrona (AES) i rendgenske difrakcije (XRD). Konstituenti uzoraka iz obje legure su ispitivani za tri različita stanja, tj. nakon izrazito brzog hlađenja, lijevanja u bakrenu kokilu i nakon diferencijalno pretražne kalorimetrije. Utvrđeno je da su se uzorci legura u lijevanom i kontrolirano hlađenom stanju sastojali od aluminijem bogate αAl-osnove, te Al10Mn3 i Be4AlMn faza. U slučaju lijevanja i diferencijalno pretražne kalorimetrije primarna je kristalizacija započela precipitacijom B4AlMn faze što se može najvjerojatnije okarakterizirati kao univarijantna binarna eutektička reakcija L > (Be4AlMn + Al10Mn3). Proces skrućivanja je nastavljen s invarijantnom ternarnom eutektičkom reakcijom, gdje preostala talina (L) stvara heterogenu strukturu (αAl + Al10Mn3 + Be4AlMn) ili ternarni eutektik. Kada su korištene izrazito velike brzine hlađenja, kao u slučaju "melt-spinning" metode, konstitutivne faze obiju legura su precipitirale u veoma malom obliku, a Be4AlMn faza bila je potpuno odsutna u obliku primarnih poligonalnih čestica i zamijenjena je "icosahedral" kristaliničnom fazom ili i-fazom. Također nema dokaza o prisutnosti Al10Mn3 faze. Raspodjela, veličina i oblik svih konstituenata u brzo-hladećim legurama su se promijenili od kontakne površine prema slobodnoj površini trakica, s manje od 0.1 µm pa do 0.5 µm kod slobodne površine. Zrna aluminijem bogate osnove imala su, blizu slobodne površine, srednji promjer manji od 20 µm, a kod kontakne površine srednji promjer zrna se smanjio na 1 µm.
Secondary keywords: kompleksne Al-Mn-Be zlitine;metalografija;strjevanje;
URN: URN:SI:UM:
Type (COBISS): Scientific work
Pages: str. 49-54
Volume: ǂVol. ǂ83
Issue: ǂno. ǂ1
Chronology: Apr. 2010
ID: 8717494