Abstract
The effect of residual stresses, induced by cold water quenching, on the morphology of fatigue crack fronts has been investigated in a powder metallurgy 8090 aluminium alloy, with and without reinforcement in the form of 20 wt-%SiC particles. Residual stress measurements reveal that the surface compressive stresses developed in these materials are significantly greater than in conventional metallurgy ingot 8090, because surface yielding occurs on quenching. The yield stresses of the powder route materials are greater than those of ingot produced 8090 and hence greater surface stresses can be maintained. In fatigue, severe crack front bowing is observed in the powder formed materials as a result of the reduction of the R ratio (minimum load/maximum load) by the compressive residual stresses at the sides of the specimen, causing premature crack closure and hence reducing the local driving force for fatigue crack growth ΔKeff. This distortion of the crack fronts introduces large errors into measurements of crack growth rate and threshold values of ΔK.
| Original language | English |
|---|---|
| Pages (from-to) | 1015-1020 |
| Number of pages | 6 |
| Journal | Materials Science and Technology |
| Volume | 7 |
| Issue number | 11 |
| DOIs | |
| Publication status | Published - Nov 1991 |
Keywords
- fatigue of materials
- fracture mechanics
- heat treatment quenching
- powder metallurgy aluminum
- silicon carbide mechanical properties
- aluminum alloy 8090
- fatigue crack growth
- aluminum and alloys