Sensitization aluminum alloys

For the elucidation of chemical reaction mechanisms, in-situ NMR spectroscopy is an established technique. For investigations at high pressure either sample tubes from sapphire [3] or metallic reactors [4] permitting high pressures and elevated temperatures are used. The latter represent autoclaves, typically machined from copper-beryllium or titanium-aluminum alloys. An earlier version thereof employs separate torus-shaped coils that are imbedded into these reactors permitting in-situ probing of the reactions within their interior. However, in this case certain drawbacks of this concept limit the filling factor of such NMR probes consequently, their sensitivity is relatively low, and so is their resolution. As a superior alternative, the metallic reactor itself may function as the resonator of the NMR probe, in which case no additional coils are required. In this way gas/liquid reactions or reactions within supercritical fluids can be studied... 

Black powder is the oldest explosive in history, dating back to the eighth century. Its chemical composition is well-known as a mixture of potassium nitrate, sulfur, and charcoal. The mixture ratio is varied according to the purpose for which it is to be used, with the ranges kno3(0-58-0.79), (0.08-0.20), and ( (0.10-0.20). Black powder composed of particles less than 0.1 mm in diameter is used for shell burst of fireworks and fuses. The grade with diameter 0.4—1.2 mm is used for the launch of spherical shells of fireworks, while that with diameter 3-7 mm is used in stone mines. Since black powder is sensitive to sparks caused by mechanical impact, friction, and static electricity, black powder containers should be made of brass or aluminum alloys rather than iron or steel. When Cl and Ca or Mg are present as impurities, CaClj or MgClj is formed and the thermal performance of KN is reduced. Contamination with NaCl also needs to be avoided for the same reason. 

The shape of the firing pin commonly used in (he US is constructed as shown in Fig F3 (Ref 1). Common firing pin materials include both. steel and aluminum alloys. Rear end of pin may be shaped in any way convenient for assembly. Alignment of pin with respect to primer and surface finish of pin ate important and affect the sensitivity (Ref 2). Fig F4 shows a typical stab detonator. For more information on stab detonators, see Vol 4, pp D844-L to D846-L... 

Various boron compounds have been used as rocket fuels, diamond substitutes, and additives to aluminum alloys to improve electrical and thermal conductivity, as well as for grain refining. Boron hydrides are sensitive to shock and can detonate easily. Boron halides ate corrosive and toxic. 

A study of the pretreatment application and the surface prior to deposition indicates that the aluminum alloy panels have a marked sensitivity to the buildup of a fluorocarbon background in the plasma reactor. This study also showed that the application of the O2 plasma treatment modified the alloy surface, changing it... 

Raney cobalt, which is prepared from a commercially available cobalt aluminum alloy in the same way as is Raney nickel, has been shown to have catalytic activity but it is generally less active than Raney nickel and more sensitive to variations in the reaction procedure and catalyst aging than the nickel catalyst. 

Lead azide reacts with copper to fonn a very sensitive cuprous azide. Polished copper strips in contact with lead azide for 9-20 days at 90% relative humidity and 50 C react. In contrast, magnesium-aluminum alloys and magnesium strips show a negligible reaction under the same conditions even after 18 months exposure [24]. 

A major reason why Zr (rather than Cr, Mn, V or Ti) has become the preferred choice as the recrystallization inhibiting element relates to its relatively low effect on quench sensitivity in commercial aluminum alloys [6],... 

Aluminum alloys, particularly the high-strength compositions, are susceptible to environmental cracking, both in aqueous environments and in air as a function of relative humidity. This susceptibility is particularly sensitive to alloy composition and thermal treatment, which is shown by differences in the dependence of ductility on strain rate. Understanding these differences can contribute to identification of mechanisms of the strain-rate sensitivity. A summary of the influence of strain rate on the ductility of 2000-, 5000-, and 7000-series aluminum alloys in environments represented by 3% NaCl + 0.3% H202 is shown in Fig. 7.84 (Ref 121). The 7000 series shows susceptibility to hydrogen embrittlement at strain rates below 10 5 to 10-6 s 1. Although there is... 

Relationship of Composition and Heat Treatment to Environment-Sensitive Cracking of Aluminum Alloys. Those aluminum alloys strengthened by cold working only, particularly the 1000-series alloys, do not develop susceptibility to SCC. The so-called high-strength alloys are strengthened by thermal/mechanical treatments, which result in solid-state precipitation of one or more intermetallic phases that restrict dislocation motion and, hence, increase strength. Their susceptibility to SCC varies extensively with alloy composition and the thermal/mechanical treatment. While susceptibility tends to increase with... 

N.J. Holroyd and G.M. Seamans, Slow-Strain-Rate Stress Corrosion Testing of Aluminum Alloys, Environment-Sensitive Fracture Evaluation and Comparison of Test Methods, STP 821, S.W. Dean, E.N. Pugh, and G.M. Ugiansky, Ed., ASTM, 1984, p 202-241... 

There is an almost infinite variety of possible tool shapes, and fabricating tool steel profiles and conducting experimental trials is expensive. Hence, the potential of modeling is particularly great in the area of tool design. Colegrove and Shercliff (Ref 45 7, 50) used the 2-D CED methods discussed in section 10.3.5, Tool Material Interface Conditions, to study a series of profiles, as illustrated in Fig. 10.9. The sensitivity of the flow pattern, torque, and traverse force to tool shape was compared for 2024, 7075, and 7449 aluminum alloys. Experimental... 

At present, the 2000(Cu), 5000(Mg), 6000(Mg-Si) series provide most of the aluminum alloys used in cryogenic applications. Established alloys in the 7000(Zn) series, including 7075, 7079, and 7178, are more sensitive to notches than many of the alloys of the above types [ 2] and have not been seriously considered. Recently, several new 7000-series alloys have been introduced with appreciably greater notch toughness than other alloys of this type. It is expected that these new alloys may be of considerable use in cryogenic applications. 

The complete comparison of these alloys cannot be gained from the curves in Fig, 2. Considerably more information is gained from a plot of notch yield ratio as a function of the tensile yield strength, as in the example in Fig. 3 for —320°F also shown are data points for other 7000 series alloys, 2014-T6 and 2219-T87, and a band for data from tests of other alloys [ ]. This plot shows that as yield strength increases, some increase in sensitivity to notches is experienced, and that the data points for most aluminum alloys fall into a narrow range. 

The relative ratings of aluminum alloys with regard to notch sensitivity are independent of the notch tip radius within the range associated with theoretical stress concentrations from 7 to 17. 

J. G. Kaufman and E. W. Johnson, The Use of Notch-Yield Ratio tq Evaluate the Notch Sensitivity of Aluminum Alloys, Am. Soc. Testing Materials Proc., 62 (1962). 

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