The current thesis was designed to examine the welding characteristics of laser and electron beam
welding of the superplastic metal matrix composites (MMCs) reinforced with 1~20% SiC and to
differentiate the difference between the 6061 aluminum alloy and 6061/SiC composites.
The 6061/20%SiCw MMC was found to exhibit poor welding characteristics under electron beam
welding. This was because that the SiC whiskers would induce poor fluidity of molten Al matrix and
the electron beam continuously bombared the MMC resulting in material loss through sputtering, and
this effect induced an "V" groove formed at the center of the fusion zone. The laser beam welding of
the 20% SiCw MMCs caused the decomposition of the SiCw into Al4C3 platelets at the center region
of the fusion zone, as well as cavities along the outer region due to thermal expansion differences.
The post-weld tensile test results showed that the brittle weld zone lead to the degradation of strength,
and the 6061/20%SiCw MMC after welding would lose superplastic properties. There were some
differences between the 6061 alloy and MMC upon subjected to laser beam welding. The absorption
of laser energy by the MMC was better than that by the alloy; the absorption of laser energy increased
with increasing SiC content. The shape of the reinforced material could also influence the quantity of
Al4C3 formed. The total surface area of SiC particles was smaller than that of the SiC whiskers under
equal volume fraction, therefore more SiC whiskers were decomposed. In the wetting experiment, the
wettability and fluidity of molten material was observed to decrease with increasing SiC volume fraction
at the same temperature. The wettability could be improved at higher temperatures. For the
20%SiCw MMC, the wettability and fluidity could not be sufficiently improved even at a high
temperature of 1300¢J, which appeared to be the cause for the lack of feeding in the central fusion zone.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0714100-101608 |
| Date | 14 July 2000 |
| Creators | Huang, Ru-Ying |
| Contributors | N. J. Ho, C. M. Cho, J. C. Huang |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0714100-101608 |
| Rights | unrestricted, Copyright information available at source archive |
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