Optical microscopy and microhardness tests on a secondary aluminium alloy. (4th August 2014)

• Record Type: Journal Article
• Authors: Britchi, M.; Olteanu, M.; Pencea, I.
• Is Part Of: International journal of material & product technology. Volume 14:Number 1(1999)
• Page Start: 17
• Page End: 27
• Publication Date: 2014-08-04
• Subjects: compaction -- hot extrusion -- hardness tests -- melt spinning -- ultrarapid quenching -- secondary aluminium alloys -- slow solidification -- optical microscopy -- microhardness -- aluminium scrap recovery -- cold pressing; Manufacturing processes -- Periodicals; Materials -- Testing -- Periodicals; 620.11
• Languages: English
• ISSNs: 0268-1900

Abstract

A study of optical microscopy and microhardness was performed on an aluminium alloy manufactured from scrap which was either slowly cooled or ultrarapidly quenched by a melt–spinning method. The alloy composition (in weight %) is: 9.52 Si, 3.80 Cu, 2.85 Zn, 2.00 Fe, 0.50 Mn, 0.30 Mg, 0.30 Sn, 0.30 Ni, 0.20 Pb, 0.10 Ti, the balance being Al. The presence in the equilibrium composition of the cast alloy of some fragilizing compounds (especially of silicon and iron) formed at these high values, much higher than solubility limits, has been evidenced by optical microscopy. Ultrarapid quenching is one of the methods used for aluminium scrap recovery. A study on a sample cast in a wedge–shaped mould was made before the ultrarapid quenching of the present alloy. The variation of the alloy structure with solidification rate is presented as optical micrographs taken starting from the broad end (16 cm) and going down to the tapered (<4 mm) end of the wedge–sample. Microhardness values along the sample are also given, and the conclusion is that microhardness rises with the increase of the solidification rate of the alloy. The alloy was quenched ultrarapidly by a melt–spinning method when tapes of different thicknesses were obtained. Due to this treatment, the alloy hardness is increased by two processes: (i) structure finishing, and (ii) an extension of solubility registered in the case of the elements considered as impurities, especially Si and Fe. The tapes manufactured from the ultrarapidly quenched alloy were then compacted by cold pressing followed by hot extrusion, when a finite product was obtained as rods of ø = 3 and respectively, ø = 4 mm diameters. The products thus obtained were studied by optical microscopy and microhardness measurements.