Abstract
A study of the influence of SiC-particulate reinforcement on ageing and subsequent fatigue crack growth resistance in a powder metallurgy 8090 aluminium alloy-SiC composite has been made. Macroscopic hardness measurements revealed that ageing at 170°C in the composite is accelerated with respect to the unreinforced alloy, though TEM studies indicate that this is not due to the enhanced precipitation of S′. Fatigue crack growth rates in the naturally aged condition of the composite and unreinforced matrix are similar at low to medium values of ΔK, but diverge above ≈ 8 MPa√m owing to the lower fracture toughness of the composite. As a result of the presence of the reinforcement, planar slip in the composite is suppressed and facetted crack growth is not observed. Ageing at or above 170°C has a deleterious effect on fatigue crack growth. Increased ageing time decreases the roughness of the fracture path at higher growth rates. These effect are though to be due to microstructural changes occurring at or near to the SiC/matrix interfaces, providing sites for static mode failure mechanisms to operate. This suggestion is supported by the observation that as ΔK increases, crack growth rates become Kmax dependent, implying the crack growth rate is strongly influenced by static modes.
| Original language | English |
|---|---|
| Pages (from-to) | 793-806 |
| Number of pages | 14 |
| Journal | Acta Metallurgica et Materialia |
| Volume | 39 |
| Issue number | 5 |
| DOIs | |
| Publication status | Published - May 1991 |
Keywords
- aluminum lithium copper alloys
- microstructure aluminum metallography
- aging time fatigue of materials
- alloy 8090
- fatigue crack growth
- silicon carbide particulate reinforcement
- fiber reinforcement
- powder metallurgy