Proposity study and effects on mechanical properties of discontinuous reinforced metal matrix composite (DRMMC)
The effects of porosity on mechanical properties of cast discontinuous reinforced meta] matrix composite (DRMMC) were investigated. Hence, a casting rig was fabricated to produce DRMMCs via conventional and modified stir casting method . The modified stir casting method performed pre-heating of r...
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| Format: | Thesis |
| Language: | English English English |
| Published: |
2004
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| Subjects: | |
| Online Access: | http://eprints.uthm.edu.my/8667/1/24p%20SYARIFAH%20NUR%20AQIDA%20SYED%20AHMAD.pdf http://eprints.uthm.edu.my/8667/2/SYARIFAH%20NUR%20AQIDA%20SYED%20AHMAD%20COPYRIGHT%20DECLARATION.pdf http://eprints.uthm.edu.my/8667/3/SYARIFAH%20NUR%20AQIDA%20SYED%20AHMAD%20WATERMARK.pdf |
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| Summary: | The effects of porosity on mechanical properties of cast discontinuous reinforced
meta] matrix composite (DRMMC) were investigated. Hence, a casting rig was
fabricated to produce DRMMCs via conventional and modified stir casting method . The
modified stir casting method performed pre-heating of reinforcement particles during
matrix alloy melting. Silicon carbide particle reinforced aluminium alloy composites
were produced with three different stirring speeds: 100, 200 and 500rpm. Cast
DRMMCs were evaluated in as-cast condition for microstructure analysis, porosity and
density measurement and mechanical testing. The mechanical properties of cast
DRMMC were determined from tensile and fatigue tests conducted at room temperature.
Tensile tests were referred to ASTM B557 standard while the axial fatigue test (ASTM
E466) was conducted at stress ratio (R) of -1. A finite element method (FEM) analysis
was carried out using Solidworks 2003 software. It was found that the major causes of
porosity occurrence in cast DRMMC were clustered silicon carbide particles, gas
entrapment and solidification shrinkage. From porosity measurement, conventionally stir
cast DRMMCs contained higher porosity compared to the modified stir cast DRMMCs.
The least content of porosity evaluated is at 0.09% in modified stir cast DRMMC, while
the highest is at 12.45% in conventionally stir cast DRMMC. Fatigue strength (at 1 x 107
cycles) of cast DRMMCs at 5, 10, and 15% reinforcing SiC particle were 129.7, 141.5
and 157.3 MPa respectively. Based on the FEM analysis, porosity in conventionally stir
cast DRMMC promotes higher von Mises stress as much as 40.2 MPa compared to 12.6
MPa in modified stir cast DRMMC. The porosity contents increased with increasing
silicon carbide particles. Higher stirring speed tended to entrap more gas during mixing,
whereas a lower stirring speed was ineffective to disperse SiC particles and results in
clustering. Increasing porosity content in cast DRMMC had decreased the density and
tensile properties ofDRMMC as depicted by the FEM analysis. Though, fatigue strength
increased as a result of existing constraints in form of porosity |
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