Thermal stability of Al-Mn-Be melt-spun ribbons

Gorazd Lojen (Author), Tonica Bončina (Author), Franc Zupanič (Author)

Abstract

As with other kinds of finely dispersed, small particles, icosahedral quasicrystals (IQCs) also have a distinct strengthening effect, which can be utilised to enhance the mechanical properties of aluminium alloys. In Al-Mn-Bealloys, IQCs already form at moderate cooling rates, which can be utilised when using some conventional casting processes, like mould or injection casting. In this case, however, crystalline intermetallic phases are also present and the mechanical properties are inferior to those of two-phase aAl-IQC alloys. Two-phase microstructures are feasible using rapid solidification techniques, e.g., melt spinning. Further processing often involves technologies (consolidation, extrusion etc.), which include the influence of heat. The alloy must not be overheated in order to preserve the strengthening effect of the metastable IQC-particles. In this investigation the Al-Mn-Be alloy was melt-spun using a free-jet melt spinner. Subsequently, the thermal stability of the IQCs was explored by annealing the ribbons for 24h at different temperatures. The samples were examined in the as-cast and heat-treated conditions using a dual-beam, scanning electron microscope (SEM-FIB), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). It was discovered that in the as-cast condition, the ribbons had a two-phase microstructure, consisting of an aAl matrix and finely dispersed IQCs. During annealing at temperatures up to 400 °C, the IQCs did not decompose and the phase composition remained unchanged. Annealing at 500 °C and at higher temperatures caused a decomposition of the IQCs, and only the crystalline intermetallic phases Al6Mn and Be4AlMn could be found in the aAl matrix.

Keywords

kvazikristali;zlitina Al-Mn-Be;temperaturna obstojnost;quasicrystal;Al-Mn-Be alloy;thermal stability;

Data

Language:	English
Year of publishing:	2012
Typology:	1.01 - Original Scientific Article
Organization:	UM FS - Faculty of Mechanical Engineering
Publisher:	Inštitut za kovinske materiale in tehnologije Ljubljana
UDC:	669.71'74'725:621.74.046
COBISS:	16153366
ISSN:	1580-2949
Parent publication:	Materiali in tehnologije
Views:	1073
Downloads:	137
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Other data

Secondary language:	Slovenian
Secondary title:	Temperaturna obstojnost hitro strjenih trakov Al-Mn-Be
Secondary abstract:	Ikozaedrični kvazikristali (IQC) imajo kakor druge vrste fino razpršenih drobnih delcev utrjevalni učinek, ki ga lahko izkoristimo za povečanje trdnosti aluminijevih zlitin. V zlitinah Al-Mn-Be kvazikristali nastajajo že pri zmernih ohlajevalnih hitrostih, kakršne dosežemo pri postopkih litja, kot sta npr. kokilno litje in tlačno litje. Toda mikrostruktura, ki nastane pri teh postopkih litja, vsebuje tudi kristalne intermetalne faze in trdnostne lastnosti so slabše kot pri zlitinah z dvofazno mikrostrukturo (aAl-IQC). Dvofazno mikrostrukturo pa lahko dosežemo le z velikimi ohlajevalnimi hitrostmi, tj. s postopki hitrega strjevanja. Nadaljnja predelava hitro strjenih materialov pogosto poteka s postopki (kompaktiranje, iztiskovanje itd.), ki zahtevajo segrevanje. Pri tem materiala ne smemo pregreti, če želimo ohraniti utrjevalni učinek kvazikristalov. V okviru te raziskave so bili uliti hitro strjeni trakovi Al-Mn-Be s postopkom prostega litja na vrteče se kolo (angl.: melt spinning). Temperaturno obstojnost trakov hitro strjene zlitine smo ugotavljali z žarjenjem 24 h pri različnih temperaturah. Mikrostrukture trakov smo analizirali v litem stanju in po toplotni obdelavi z vrstičnim elektronskim mikroskopom z elektronskim in ionskim curkom (SEM-FIB), rentgensko difrakcijo (XRD) in z diferenčno dinamično kalorimetrijo (DSC). Trakovi so imeli v litem stanju dvofazno mikrostrukturo, sestavljeno iz matice aAl in fino dispergiranih kvazikristalov. Žarjenje pri temperaturah do 400 °C ni povzročilo razpada kvazikristalov in fazna sestava je ostala nespremenjena. Po žarjenju pri 500 °C ali višjih temperaturah pa je bila mikrostruktura sestavljena iz matice aAl in kristalnih intermetalnih faz Al6Mn ter Be4AlMn.
Secondary keywords:	kvazikristali;zlitina Al-Mn-Be;temperaturna obstojnost;
URN:	URN:NBN:SI
Type (COBISS):	Scientific work
Pages:	str. 329-333
Volume:	ǂLetn. ǂ46
Issue:	ǂšt. ǂ4
Chronology:	jul.-avg. 2012
Keywords (UDC):	applied sciences;medicine;technology;uporabne znanosti;medicina;tehnika;chemical technology;chemical and related industries;kemijska tehnologija;kemijske in sorodne industrije;metallurgy;metalurgija;applied sciences;medicine;technology;uporabne znanosti;medicina;tehnika;engineering;technology in general;inženirstvo;tehnologija na splošno;mechanical engineering in general;nuclear technology;electrical engineering;machinery;strojništvo;mechanical technology in general: processes;tools;machines;equipment;obdelava z deformacijo;obdelava brez odrezovanja;toplotna obdelava;
ID:	1439098