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Continuous and cyclic thermal exposure induced degradation in boron reinforced 6061 aluminum compositesBoron reinforced 6061 aluminum (B/Al) composite was continuously exposed at 728 K for up to 240 hours and cyclically exposed between 293 K and 728 K for up to 6000 three-minute cycles. Room temperature tensile strengths were measured and the specimens were metallographically examined. The data suggest that, in addition to AlB2 formation, magnesium in the matrix diffused to the reaction layer and formed (Al,Mg)B2. This formation could weaken the matrix and embrittle the reaction layer. Continuous exposure degraded the strength of the B/Al specimens about 28% in 240 hours. However, the fracture mode, one indicative of high strength interfaces, did not change. The strength degradation was attributed to crack initiation in the brittle reaction layer causing stress concentrations in the fibers. Cyclic exposure degraded the strength of the B/Al about 34% in 6000 cycles. The fracture mode of the cyclic exposure specimens showed transition toward a mode characteristic of low interfacial strength. The lower interfacial strengths were attributed to stress fields induced by differential thermal expansion. Cyclic exposure degraded the strength of the B/Al specimens more than continuous exposure for similar cumulative exposure times.
Document ID
19780040990
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Olsen, G. C.
(NASA Langley Research Center Hampton, VA, United States)
Tompkins, S. S.
(NASA Langley Research Center Hampton, Va., United States)
Date Acquired
August 9, 2013
Publication Date
October 1, 1977
Subject Category
Composite Materials
Meeting Information
Meeting: Fall Meeting
Location: Chicago, IL
Start Date: October 23, 1977
End Date: October 27, 1977
Sponsors: Metallurgical Society of AIME
Accession Number
78A24899
Distribution Limits
Public
Copyright
Other

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