A Study of the Fatigue, Impact and Fracture Toughness Characteristics of Electroslag Refined IS: 7670 Alloy

Abstract

The nuclear, aerospace, naval and missile industries place emphasis on materials with high structural integrity and reliable performance so as to meet certain stringent requirements in service. Strength is not the only criterion for selection. Properties such as fatigue resistance, impact toughness and fracture toughness. are equally important. Electroslag refining (ESR) has been used widely and successfully over the years for improving the fatigue resistance, creep resistance, impact strength and fracture toughness of steels and alloy steels. But application of ESR to aluminium alloys is only a recent endeavour. A highstrength aircraft aluminium alloy IS: 7670 was therefore chosen for studies on the fatigue strength and the impact and fracture toughness. The results indicate that the fatigue resistance is considerably improved after refining and that the impact strength and fracture toughness of the refined alloy are comparable with that of the unrefined alloy.Resume-Les industries nucleaire, aerospatiale et navale s'interessent gran dement aux materiaux presentant une tres grande intetrite structurale ainsi qu'une performance fiable, afin de satisfaire certaines exigences rigoureuses en service. La resistance mecanique n'est pas Ie seul critere de selection. Des propeietes comme la resistance a la fatigue, la resistance a l'impact ainsi que la tenacite sont egalement importantes. L'affinement par electroslag (ESR) est un procede qui a ete couramment utilise avec succes dans Ie passe pour ameliorer la resistance a la fatigue et au fluage ainsi que la resistance a l'impact et la tenacite d'aciers et d'aciers allies. Par contre, l'application du ESR aux alIiages d'aluminium est uneffort relativement recent. Le IS: 7670, un alliage d'aluminium a haute resistance pour applications aeronautiques, a donc ete choisi pour les etudes de fatigue et de tenacite. Les resultats montrent que la resistance a la fatigue est considerablement amelioree apres ESR et que la resistance a l'impact et la tenacite de l'alliage affine sont comparables a celles de l'alliage non affine.