Microstructure characteristics in Al-C system after mechanical alloying and high temperature treatment

Abstract

containing copper scraps at 475°C) was also connected to the Institute of Materials, Minerals and Mining. the mill. Steel ball/powder ratio was 205 1 and the optimum speed of the high energy ball mill was around 600 rev minÕ 1.To arbitrate the eVect of processing time on the eYciency of MA, powders were treated for 0•5-2 h under a protective

Microstructure and electrical resistivity features in Al-Al4C3 in-situ composite after attrition milling and double sequence of compaction and high temperature treatment

“…On the average, The average cluster size is 39 nm and mean spacing between the clusters is 118 nm. Thus, compared to previous work [21,22], precipitates are finer and more closely spaced. …”

“…A little knowledge is that these neutral ceramic particles are very stable and resistant to 'Ostwald Ripening' during prolonged annealing [19] and they have significantly high room temperature self electrical resistivity values [34]. The information obtained with TEM technique through the previous [21,22] and present works nevertheless draw attention, that rise in electrical resistivity of Al can be attributed to the increase in distribution and density of the Al 4 C 3 precipitation in the matrix. Presumably, rather than the size and spacing of distinctive precipitates [19], the dimension of the non-random Al 4 C 3 clusters and the spacing between them govern the electrical resistivity.…”

“…By elemental diffusion, atomic C penetrated in and located at interstitial sites of the convoluted crys- tal structure of Al. This was either due to very short milling time resulting inadequate synthesizing time for the formation of the Al 4 C 3 phase [19][20][21][22]26] or due to the amorphous phase of Al 4 C 3 that formed before crystallization [20,27,28]. Consequently, development of Al 4 C 3 was thermodynamically impractical during MA [28].…”

“…At the end of 2 h MA, both mean particle size (18.58 µm) and lamellae spacing became smaller (less than 3 µm in size). At this stage, free C dust possibly extruded in and coated the interface of the multilayered lamellae structure [21,22]. Further attempts to increase the attrition time failed, because mean Al powders size became less than 10 µm and so the flammability of these fine Al dusts increased intensively.…”

“…Recent researches reveal that addition of fine oxides and carbides can contribute to high temperature strength together with advanced toughness, fatigue and corrosion properties [16]. Some preliminary studies were concentrated on in-situ Al composites reinforced by fine Al 4 C 3 and Al 2 O 3 precipitates, where results reveal these particles have considerable effects on optimum mechanical properties of the materials [17][18][19][20][21][22][23][24][25]. In several alloy systems, synthesizing of these stable precipitates through MA process is gaining interest in the last decade.…”