Al-based alloys

As we show in Fig. 2 this relation holds as well for the two Al-based alloys studied here. This finding has consequences on the nature of the inter-atomic interactions. From a fee point of view, the hep structure has a stacking fault every second layer. The fact that relation (1) holds means that these stacking faults weakly interact, and therefore the range of the inter-atomic interactions should not go beyond the second neighbor shell whereas conventional central potentials require at least three atomic shells to differentiate the fee and hep stacking sequences. 

Scully, J.R., Young, G.A. Jr., and Smith, S.W., Hydrogen solubility, diffusion and trapping in high purity aluminum and selected Al-base alloy. Mater. Sci. Forum, 331-337, 1583, 2000. 

Bodies — A1 or Al base alloys if LA is used as an ingredient of a charge and Cu or Cu alloys (such as gilding metal) for chges contg MF... 

The oxidation resistance of TiAl alloys can be improved by special pre-oxidation treatments (Suzuki etal., 1991). Alternatively, it can be improved by alloying with Nb, Ta, and W which, however, reduces the ductility whereas V, Cr, and Mn, which are used for increasing ductility, reduce the oxidation resistance (Kim, 1989). Ti Al-based alloys with high contents of Nb have been studied recently with respect to the conditions for protective scale formation, and indeed protective oxidation has been found at 1400°C for an Al content of 50 at.% (Brady et al., 1993). In view of the oxidation problems of the titanium alu-minides a coating has been proposed for providing sufficient oxidation protection, and various approaches have been studied (Nishiyama etal., 1990 Taniguchi etal., 1991 b Yoshiharaet al., 1991 Wuand Lin, 1993). 

An example of elemental depletion that promotes IGC and stress corrosion is grain boundary Cu depletion in Al-Cu, Al-Cu-Mg, and Al-Cu-Li alloys (see below). Beneficial Cu is depleted from the Al-rich matrix near the grain boundaries and collected at S-A Cu, 5 -Al2CuMg, and Ti-Al2CuLi precipitate phases, respectively. This is discussed further below under the sections referring to Al-base alloys. 

Heat-treatable Al-base alloys are often overaged using a duplex heat treatment to improve IGC, IGSCC, and/or exfoliation resistance. However, the loss in peak strength makes this practice undesirable. 

Studies have been carried out on the mechanical properties of many structural materials under static and dynamic loading in the temperature range 4 to 300 K. The results obtained for Ti- and Al-based alloys and for some stainless steel are briefly described. 

Aluminum possesses good electrical and thermal conductivity as well as its durability and availability makes it a preferable material for various microelectronics and MEMS applications. EMM of patterned A1 and Al-based alloys can be utilized in a wide range of applications, which includes energy storage devices microanalytical systems and microfluidic, optical, and microelectronic devices. EMM is economical and scalable to large geometric areas platform for microstructuring of A1 substrates. 

Figure 17.7 The length of the incubation crack as a function of the stress amplitude B - an Al-based alloy C - a Ti-based alloy D - a low-alloy steel E - a superalloy F - a stainless steel. See Table 17.1 for details.

Table 3.1-25 Selected tensile data for yield stress R, fracture stress R. total elongation A, fracture toughness K c at room temperature, and creep time to rupture at 650 °C and 380 MPa for various Tis Al-based alloys...

---