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High‐resolution electron microscope observation of interface microstructure of a cast Al‐Mg‐Si‐Bi‐Pb(6262)/Al 2 O 3p composite
Author(s) -
Zhou Z.,
Fan Z.,
Peng H. X.,
Li D. X.
Publication year - 2001
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1046/j.1365-2818.2001.00834.x
Subject(s) - nucleation , microstructure , materials science , aluminium , particle (ecology) , composite number , metal , crystallography , composite material , chemical engineering , metallurgy , chemistry , oceanography , organic chemistry , engineering , geology
High‐resolution electron microscopy was employed to characterize the interface structure of a cast Al‐Mg‐Si‐Bi‐Pb aluminium(6262)‐based composite reinforced by α alumina particles with a trace of β alumina in order to investigate the behaviour of alloying elements in cast composites. Except for a few primary Mg 2 Si particles, few reaction products were detected at the interface of Al/α‐Al 2 O 3 due to the unfavourable reaction kinetics during the squeeze‐casting process. The Mg 2 Si particle has an orientation relationship with α‐Al 2 O 3 of [011] Mg2Si //[1 2 10] α‐Al2O3 (1 1 1) Mg2Si //(0006) α‐Al2O3 . A significant amount of MgAl 2 O 4 was found on the surface of the β‐Al 2 O 3 particles, which is in contrast to the small degree of reaction found on α‐Al 2 O 3 particles. MgAl 2 O 4 and β‐Al 2 O 3 particles have the following orientation relationship: [011] MgAl2O4 //[1 2 10] β‐Al2O3 (1 1 1) MgAl2O4 //(0006) β‐Al2O3 . The similar crystal structure of β‐Al 2 O 3 to MgAl 2 O 4 favours MgAl 2 O 4 nucleation and growth on the surface of β‐Al 2 O 3 . Interfacial energy minimization dominates the atomic structure of the interface with the result that close packed planes and directions in the Al 2 O 3 reinforcement and reaction products are parallel to the interfaces. Bi and Pb were found in the form of metallic nanometre particles between Al 2 O 3 particles, or between the MgAl 2 O 4 and Al 2 O 3 particles, or in the open channels of β‐Al 2 O 3 filled by the Al matrix.