Cast aluminum alloys

Prior to its addition to the aluminum casting alloys, the strontium metal is usually alloyed into the form of a master alloy. These master alloys are typically 10% Sr—90% A1 or 90% Sr—10% Al, and improve the dissolution and handling characteristics of strontium in the foundry. 

TABLE 3. NOMINAL CHEMICAL COMPOSITION1 AND TYPICAL PROPERTIES OF SOME ALUMINUM CASTING ALLOYS... 

Some nominal chemical composition of aluminum cast alloys and their tensile properties are listed in Table 4.22 and 4.23, respectively. 

Table 4.23 Typical tensile properties of representative aluminum casting alloys in various tempers3...

T. Din and J. Campbell, High Strength Aerospace Aluminum Casting Alloys A Comparative Study, Mater. Sci. Technol, Vol 12, 1996, p 644-650... 

Aluminum cast alloys Aluminum wrought alloys Chip formation Cutting forces Surface integrity... 

Fifty years ago, intergranular corrosion of the zinc—4% aluminum casting alloys was a problem because of high impurity levels, notably of lead, tin, and cadmium. The subsequent introduction of 99.99% zinc as the base for these casting alloys eliminated intergranular corrosion under normal service conditions. However, an inherent tendency for intergranular corrosion exists, and this defect can still occur if pure zinc-aluminum alloys are exposed to temperatures above about 70°C under wet or damp conditions. Research has... 

In practice, the use of zinc-aluminum casting alloys should be restricted to below 70 C and impurities controlled to within specific limits recent work indicates that these limits can be safely extended to 0.006% each for lead and cadmium and to 0.(X)3% for tin. 

Many plant atmospheres are contaminated by either acidic or alkaline fumes. The ZA alloys can be expected to perform better than pure zinc in acid-contaminated industrial plants. With alkaline contamination, both zinc and the ZA alloys are more suitable than aluminum casting alloys. Controlled trials made by Noranda at Kraft process pulp and paper mills (Table 2.33) showed that all the ZA alloys (and zinc) were suitable for use in each of the... 

Raising the temperature increases die dissolution of zinc and the ZA alloys (Belisle and DuFresne, 1986) in water. A marked increase occurs up to about 60°C, followed by a decrease at higher temperatures. Intergranular corrosion of the zinc-aluminum casting alloys is a risk above about 70 C in wet or humid conditions (e.g., in steam), when no protective layer can form and selective dissolution of the structure occurs. A steam test at 95°C is indeed a standard method of checking whether alloys have been correctly produced. 

Selecting Tensile Strengths of Aluminum Casting Alloys... 

Tawe 572. Selecting Tensile Strengths oe Aluminum Casting Alloys (sheet i oe s)... 

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