Al-Cu alloy

Modifications to Precipitates. Silicon is sometimes added to Al—Cu—Mg alloys to help nucleate S precipitates without the need for cold work prior to the elevated temperature aging treatments. Additions of elements such as tin [7440-31-5] Sn, cadmium [7440-43-9] Cd, and indium [7440-74-6] In, to Al—Cu alloys serve a similar purpose for 9 precipitates. Copper is often added to Al—Mg—Si alloys in the range of about 0.25% to 1.0% Cu to modify the metastable precursor to Mg2Si. The copper additions provide a substantial strength increase. When the copper addition is high, the quaternary Al CuMg Si Q-phase must be considered and dissolved during solution heat treatment. 

Figure 3 Compositional dependence of the stacking fault energy calculated from the rigid-band model (solid line) compared with the more accurate results from the LKKR-CPA calculation (dashed line) for the Al-Cu alloy system.

The effect of rapid solidification on the specific surface area is shown in Fig. 6. The specific surface area of RWA specimens increased with increase of Pd content. It was up to 3 times larger than that of the slowly solidified specimens. The addition of Pd and rapid solidification for Pd added Al-Cu alloy was quite effective in increasing the specific surface area. Figure 7 shows the conversion ratio from to acrylonitrile to acrylamide. Similarly, it was about 1.5 times higher than that of... 

Figure 22.8 Dendrite tip velocity vs. tip radius for an Al/Cu alloy. The diffusion-limit portion of the curve is unaffected by capillarity. The capillarity limit indicates the point where the tip curvature causes the dendrite growth to stop. From Kurz and Fisher [3],...

This complex form of precipitation in the Al-Cu system is of great practical importance. The finely dispersed precipitates act as effective barriers to the glide movement of dislocations during plastic deformation and harden and strengthen the material. This has led to the development of a number of widely used precipitation-hardened Al-Cu alloys [1]. 

In this example (Section 7.5.18) ATM rather than STM was used. Whereas STM depends on electron transfer between the specimen and the tip of the probe, AFM depends only on mechanical forces and is independent of the conductance of the specimen, and this may be an advantage for alloys of A1 with oxides that show poor conductance. In other experiments AFM images of an Al-Cu alloy immersed in 1M HC1 were recorded. After 24 hr new pits were formed and the ones formed earlier have grown. After 6 hr the sample was severely damaged and the surface is very rough. 

Pits are found to develop particularly in the region of grain boundaries which themselves are readily open to attack ( intergranular corrosion ). Thus, it is the Cu-depleted regions that are the major cause of the intergranular damage of Al-Cu alloys. The A1 itself remains passive for a certain time and potential, but even when... 

Among the material properties of great importance and concern is design and choice of the material and its inherent resistance to corrosion. Significant and extensive experimental data on the corrosion rates of readily available metals and their alloys can be found in the literature.35,36 The relative corrosion resistance of some steels, nickel, brass, nickel-copper alloys and Al-Cu alloys in chosen atmosphere35 is shown in Table 1.13. 

Piersma BJ (1994) The electrodeposition of Al-Cu alloys from room-temperature chloroaluminate electrolytes. Proc Electrochem Soc 94 415-428... 

Wolverton C., First-Principles Prediction of Equilibrium Precipitate Shapes in Al-Cu Alloys, Phil. Mag. Lett., 79, 683 (1999). 

Aluminum is often used as an alloy with a few atomic % Si and/or Cu to reduce electromigration (Fig. 1). This alloy is difficult to etch because copper does not form readily volatile compounds [73]. Fleating of the wafer to some 200 °C and intense ion bombardment to sputter off involatile products are then necessary to effect etching. Residual chlorine remaining on the wafer after aluminum etching can be deleterious because it can promote corrosion, especially in Al-Cu alloys. Hence wafer rinsing with DI water is common. Dry passivation by exposure to a fluorocarbon plasma has... 

---