Thermal expansion behavior of aluminum alloys reinforced with alumina planar random short fibers

Citation
He. Nassini et al., Thermal expansion behavior of aluminum alloys reinforced with alumina planar random short fibers, J MATER SCI, 36(11), 2001, pp. 2759-2772
Citations number
39
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science","Material Science & Engineering
Journal title
JOURNAL OF MATERIALS SCIENCE
ISSN journal
0022-2461 → ACNP
Volume
36
Issue
11
Year of publication
2001
Pages
2759 - 2772
Database
ISI
SICI code
0022-2461(2001)36:11<2759:TEBOAA>2.0.ZU;2-U
Abstract
The thermal expansion behavior of two aluminum alloys (Al-4%Cu and Al-12%Si ) reinforced with alumina planar random short fibers has been studied, both experimentally and theoretically. The metal matrix composites (MMCs) were manufactured by pressure infiltration of molten metal into short fiber pref orms with a planar random distribution of fibers. Dilatometric testing was used to investigate the influence of fiber volume fraction and architecture , and the effects of thermal cycling between 25 degreesC to similar to 560 degreesC. Thermal expansion measurements showed that, by increasing the fib er content in the composites, both the thermal strains and the effective co efficient of thermal expansion (CTE) were reduced in the whole temperature range. Furthermore, the thermal strains of MMCs increased almost linearly u p to a critical temperature, T(c)r, where the metallic matrix began to yiel d macroscopically due to internal thermal stresses. For temperatures higher than T(c)r the thermal strains of MMCs showed a marked hysteresis during h eating/cooling cycles due to the elasto-plastic response of the metallic ma trix. In this temperature range, the thermal expansion curves deviated appr eciably from linearity and the planar (in the plane of fibers) and transver se (normal to the plane of fibers) responses were very different: while the planar CTE was strongly reduced, the transverse CTE increased sharply with temperature, being even larger than the CTE of the unreinforced alloy. The rmal cycling produced a net dimensional change of composites during the fir st 2-3 cycles but, on the subsequent cycles, the permanent deformation disa ppeared almost completely and the successive thermal expansion curves were identical. Experimental results were compared to the theoretical prediction s of an analytical model based on the Eshelby's equivalent inclusion method , and an excellent agreement was obtained. (C) 2001 Kluwer Academic Publish ers.