In-situ TEM Studies: Heat-treatment and Corrosion

Transmission electron microscopy (TEM) has been well known as a powerful characterisation tool to understand the structure and composition of various materials down to the atomic level. Over the years, several TEM studies have been carried out to understand the compositional, structural and morphological changes a material undergoes as a...

The role of magnesium in the electrochemical behaviour of 5XXX aluminium-magnesium alloys

An investigation concerning the effects of magnesium on the intergranular corrosion susceptibility of AA5XXX aluminium alloys was carried out. In the present work, magnesium is found to be highly mobile in the bulk metal as well as in the aluminium oxide. This mobility is also found to be dependent on the temperature and bulk magnesium...

Variability of fatigue crack growth properties for 2024-T3 aluminium alloy

Discussions between D-BAA and the NLR have shown that significant variability in fatigue crack growth properties is possible for the industry standard damage tolerant aluminium alloy, 2024-T3 sheet. This is important for two reasons: (1) design assumptions and (2) comparisons of different candidate materials, such as 6013-T6, with 2024-T3....

Outdoor corrosion testing of aluminium-lithium alloys

Outdoor corrosion and stress corrosion tests were conducted on Al-Li plate and sheet materials for 3 and almost 5 years respectively. The results can be summarized as follows: Corrosion: Peak aged XXXA-T651 (8090-T651) exhibited greater exfoliation corrosion resistance than 2024-T351 and 2324-T39 plate. 2091-T3 and 2024-T3 sheet were found to be...

Effects of cooling rate on corrosion properties of high strength aluminium alloys under atmospheric conditions

Long-term outdoor exposure tests were done to investigate the effect of cooling rate on corrosion and stress corrosion properties of extruded rods of the high strength aluminium alloys 2024-T4, 2023-T6, 7075-T6 and 7075-T73. The 2024 alloy exhibited a high susceptibility to SCC irrespective of best treatment and cooling rate, whereas 7075-T6 was...

Spacecraft sustained load fracture control

The opportunities for sustained load fracture control in spacecraft are indicated. Emphasis is given to verification by small-scale laboratory testing.

Corrosion fatigue crack arrest in aluminium alloys

The economic life of airframes is largely determined by widespread initiation and growth of fatigue cracks at low stress intensities. Any factor reducing the low stress intensity fatigue damage rate could, if controllable, increase the structural durability. One such factor is corrosion fatigue crack arrest. Corrosion product build-up within a...

Engineering property comparisons of PM and IM aluminium alloy forgings

Engineering properties of the PM alloy 7091-T7E69 and the IM alloys 7075-T73, 7175-T736, 7010-T736 and 7050-T736 were compared. The properties considered were strength, fracture toughness, fatigue strength, fatigue crack propagation resistance under constant amplitude and spectrum loading, stress corrosion crack initiation and propagation...

Review of aeronatical fatigue investigations in the Netherlands during the period march 1977 - february 1979

Paper presented at the 16th ICAP Conference, Brussels, 14 and 15 May 1979.

Evaluation of non-destructive inspection methods applied to milled step-down areas

The present report describes how fatigue cracks were produced in 102 specimens. After cracking these specimens were inspected non-destructively by means of eddy currents, ultrasonics. X-rays and penetrants, and the indications were recorded. Successively the specimens were exposed to corrosion whereafter the inspections were repeated. Upon...

Aluminium alloys for advanced structural applications in transport aircraft

This paper concisely reviews and discusses (1) metallurgically cleaner alloys like -2124, 2048 and 7475, (2) potential application of 7000 series alloys in tension panels, (3) development of high strength stress corrosion resistant thick section materials like 7010, 7049 and 705O, (4) powder metallurgy 7000 series alloys with high strength and...

Heat treatment studies of aluminium alloy forgings of the AZ 74.61 type. Interim report no. 3: Fatigue crack propagation performance under manoeuvre spectrum loading

The fatigue crack propagation performance of the alloy AZ 74.61 under manoeuvre spectrum loading was studied. The crack propagation behaviour was also compared with that of the American forging alloy AA 7050, not only for simulated manoeuvre loading but also for simulated gust loading and programme loading. It was found that, at comparable...

Heat treatment studies of aluminium alloy type 7050 forgings. Interim report no. 2: The effect of heat treatment on a variety of engineering properties

The effect of variety of heat treatments on various engineering properties was studied with the aim to derive an optimum heat treatment. The engineering properties comprised Vickers hardness, short-time tensile strength, fatigue crack propagation resistance, fracture toughness and stress corrosion resistance. The test results were compared with...

Heat treatment and SCC susceptibility of AU4SG type forged material

Material from forgings rejected after cracking in service was given a variety of heat treatments. Material aged to peak hardness was susceptible to SCC at all ageing temperatures. Overageing at temperatures around 160° C imparted a significant increase in SCC resistance while useful strength was retained. An additional one week ageing at 160° C...