Aluminum-copper alloys, phase

Corrosion of Aluminum by Halogenated Solvents. Both liquid and vapor-phase halogenated solvents used for the production of ICs and PCs corrode aluminum-containing components. Water contamination of the solvent increases the time to corrosion on the one hand and increases the corrosion rate on the other hand. Dilution of the stabilized solvents with alcohol results in the breakdown of halogenated solvents and the decomposition product, chloride ion corrodes aluminum, and aluminum-copper alloys. 

The 2xxx (aluminum-copper) alloy series started to be used frequently with the development of 24S (2024) in 1933 for maximum solubility of alloying elements in the solid phase. Due to their high strength, toughness and fatigue resistance, modifications of 24S are widely used today for aircraft applications. However, the alloys of these series, in which the copper is major alloying element, are less corrosion-resistant than the alloys of other series. Copper increases the efficiency of the cathodic counter reaction of the corrosion, such as O2 and H+, reduction reaction and, thus, the presence of copper increases the corrosion rate. ... 

Corrosion activity may develop because of some heterogeneity in the grain boundary structure. In aluminum-copper alloys, precipitation of AI2CU particles at the grain boundaries leaves the adjacent solid solution anodic and more prone to corrosion. With aluminum-magnesium alloys, the opposite situation occurs, since the precipitated phase Mg Als is less noble than the solid solution. Serious intergranular attack in these two alloys may however be avoided, provided that correct manufacturing and heat treatment conditions are observed. 

Aluminum-copper-lithium alloys, 2 321 equilibrium and metastable phases, 2 322t S-Aluminum-copper-magnesium alloy, 2 318-320... 

Dealuminification. Recent investigations have shown the importance of the dealloying of S-phase (Al2CuMg) particles on the corrosion of aluminum aircraft alloys, specifically aluminum alloy 2024-T3. In 2024-T3, the S-phase particles represent approximately 60% of the particle population. These particles are of the order of 1 pm diameter, with a separation of the order of 5 pm representing an surface area fraction of 3%.56 The selective removal of aluminum and magnesium from these particles leaves behind a porous copper particle that becomes the preferential site for oxygen reduction.57, (Corcoran)5... 

Since classical Cu/ZnO catalysts exhibited a poor stability while the addition of alumina resulted in much better systems, it was tempting to add alumina to Cu-Ce intermetallic compounds. Jennings et al. (1992a), prepared ternary Cu-Ce-Al alloys of various compositions and also tried a variety of other metals (Ca, Cr, Mn, Pd, Zn). Among these ternary alloys aluminum-containing catalysts were the best. In spite of lower initial activities as compared to binary alloys, they exhibited a much better long-term stability. It is believed that the role of aluminum is to stabilize the disperse copper-ceria phases responsible for methanol synthesis activity, although the mechanism for such a process remains unclear. 

Copper alloys containing more than 8% A1 may be subjected to the preferential dissolution of aluminum component of the alloy. The a-phase... 

Copper-tin alloys (76 Cu-22 Zn-2 Al), also known as tin bronze, show increased corrosion rates with increased temperature compared to Cu-Al alloys. The corrosion resistance of copper-aluminum alloys increases with increasing aluminum content. Alpha alloys (or-aluminum bronze) consists of single (alpha) phase up to 7% aluminum and two phase (or -t- or a -f y) above 7%. Aluminum bronzes exhibit an outstanding resistance to corrosion in seawater and offer a good resistance to impingement corrosion. 

The effect of a second phase is demonstrated in the copper—aluminum system, where increasing aluminum concentration causes the alloy system to change to a polyphase alloy. By obtaining a fine dispersion of the phase, the yield strength is increased from 225 to 480 MPa (33,000—70,000 psi). 

---