Al-Si-Fe粉末合金の大気,真空環境における疲労き裂進展速度とき裂開閉口挙動

Fatigue crack growth tests were carried out on P/M (Powder Metallurgy) Al-Si-Fe alloy in vacuum and in air under ΔK-increasing and-decreasing conditions, and crack growth rates and crack closure behavior were investigated in detail by using the unloading elastic compliance method. The effect of anisotropy of the material due to extrusion process on crack growth characteristics was also examined. Fatigue crack growth resistance in terms of ΔK and ΔKeff was usually increased in a vacuum. The degree of increase, however, was found to depend on crack growth direction in relation to the anisotropy of the material and on crack growth rate regime. Crack opening point was different between material anisotropy directions but could well be correlated to the roughness of fracture was dominant in air, while that in vacuum was found to take similar values irrespective of material anisotropy directions and of macroscopic appearance of the fracture surface.