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Effect of cooling rate on the constitution of Al-Mn-Be-Cu
| Content Provider | Semantic Scholar |
|---|---|
| Author | Naglič, Iztok Karpe, Blaž Markoli, Boštjan |
| Copyright Year | 2012 |
| Abstract | In this article the constitution of the Al-Mn-Be-Cu alloys and the influence of the cooling rate on the constitution was studied. Cooling rates were determined through the measurements of the dendrite arm spacing and the heat calculations. By the use of computer program which is part of the light microscopy technique, individual fractions of i-phase were determined. It was found that at cooling rates between 500 K s–1 and 1 350 K s–1 the preferred phase formed was a quasicrystalline phase – especially in the form of the quasicrystalline eutectic (αAl + i-phase). In addition to the quasicrystalline i-phase within eutectic, it is also formed as the primary phase. The fraction of the i-phase varied depending on the diameter of the castings (2 mm and 4 mm) and in most cases it increased with the decreasing diameter. Fractions of the i-phase in the individual castings were higher in the alloy with a higher content of manganese. Morphology of the i-phase depended on the content of the alloying elements and the cooling rate. Thus in the alloy with a higher mole content of the manganese (4.5 at. % Mn) i-phase possessed the dendritic form, while in the alloy with lower manganese content (1.8 at. % Mn) it was in form of needles, which were thicker at the tips. With the distance from the edge of the sample (with decreasing cooling rate) the dendrites grew, the primary branches were thicker and the secondary branches started to grow also. In the case of the needle morphology, the length and the thickness of needles grew with increasing distance from the sample edge. Izvleček: V članku je obravnavana konstitucija dveh zlitin Al-Mn-BeCu in vpliv ohlajevalne hitrosti nanjo. Opravljene so bile ocene 358 Štrekelj, N., Naglič, i., karpe, B., Markoli, B. RMZ-M&G 2011, 58 ohlajevalnih hitrosti z merjenjem sekundarnih dendritnih razdalj in izračunov toplotne bilance strjevanja. Z računalniškim programom, ki je del svetlobnomikroskopske opreme, so bili določeni površinski deleži faze i v ulitkih. Ugotovljeno je bilo, da je pri ohlajevalnih hitrostih med 500 K s–1 in 1350 K s–1 prednostna tvorba kvazikristalne faze (zlasti v obliki kvazikristalnega evtektika (αAl + faza i)). Poleg kvazikristalne faze i v okviru heterogenega zloga se le-ta pojavlja tudi kot primarna faza. Delež faze i se spreminja glede na premer ulitih valjčkov (2 mm in 4 mm) in v povprečju raste s padajočim premerom. Deleži faze i v posameznih ulitkih so višji pri zlitini z višjim deležem mangana. Morfologija faze i se spreminja v odvisnosti od vsebnosti zlitinskih elementov in hitrosti ohlajanja. Tako je v zlitini z višjim deležem mangana (4,5 at. % Mn) faza i prisotna večinoma v dendritni obliki, medtem ko je v zlitini z nižjo vsebnostjo mangana (1,8 at. % Mn) v obliki iglic, ki so na koncu odebeljene. Z oddaljenostjo od roba vzorca, torej v odvisnosti od ohlajevalne hitrosti, pa dendriti rastejo, primarne veje se debelijo, sekundarne začno rasti. Pri igličasti morfologiji pa dolžina in debelina iglic z oddaljenostjo od roba vzorca rasteta. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://www.rmz-mg.com/letniki/rmz58/RMZ58_0357_0366.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
