Volume 09 - Metallography and Microstructures Part 8 ppsx

Fig. 123 Haynes 21 casting aged 24 h at 870 °C (1600 °F). M 7 C 3 particles and precipitated M 23 C 6 at grain boundaries and in grains of fcc matrix. See also Fig. 124. Electrolytic etch: HCl. 500× Fig. 124 Replica electron micrograph of Fig. 123. Massive primary M 7 C 3 particle and secondary precipitate of M 23 C 6 at grain boundaries and within grains. Electrolytic etch: HCl. 3000× Fig. 125 Haynes 31, as-cast. Structure consists of large, primary M 7 C 3 particles and grain-boundary M 23 C 6 in an α (fcc) matrix. See also Fig. 126 and 127. Electrolytic etch: 2% CrO 3 . 400× Fig. 126 Haynes 31, as-cast thin section, aged 22 h at 730 °C (1350 °F). Precipitated M 23 C 6 at grain boundaries and adjacent to primary carbide (M 7 C 3 ) particles. Electrolytic etch: 2% CrO 3 . 400× Fig. 127 Haynes 31, as-cast thick section, aged 22 h at 730 °C (1350 °F). Large particles are M 7 C 3 ; grain- boundary and mottled dispersions are M 23 C 6 ; fcc matrix. Electrolytic etch: 2% CrO 3 . 500× Fig. 128 Haynes 151, as-cast. Structure consists of dispersed islands of large primary carbide (M 6 C) in the α (fcc) matrix. See also Fig. 129. Electrolytic etch: HCl and CrO 3 . 200× Fig. 129 Same as Fig. 128, but at higher magnification, which reveals details of the M 6 C (note the lamellar form) in the α (fcc) matrix. Electrolytic etch: HCl and CrO 3 . 500× Fig. 130 Haynes 151 casting aged 16 h at 760 °C (1400 °F) M 6 C particles and precipitated M 23 C 6 at grain boundaries and next to M 6 C particles in the fcc matrix. Electrolytic etch: HCl and CrO 3 . 500× Fig. 131 Fig. 132 Fig. 133 98M2 Stellite, as-investment-cast ring. Microstructure consists of large primary carbides in a matrix of secondary carbides and cobalt-chromium-tungsten solid solution. Some primary carbides have solidified in a star-like array. Electrolytic etch: 50% HNO 3 . Fig. 131: 100×; Fig. 132: 500×; Fig. 133: 1000×. (S.E. Wall and R.L. Snyder) Fig. 134 Fig. 135 Fig. 136 98M2 Stellite, as-investment-cast bar. Very large primary carbides in a matrix of smaller secondary carbides and cobalt-chromium-tungsten solid solution. Electrolytic etch: 50% HNO 3 . Fig. 134: 100× Fig. 135: 500×; Fig. 136: 1000×. (S.E. Wall and R.L. Snyder) Fig. 137 WI-52, as-cast. The solid gray islands are complex chromium- tungsten carbide; particulated islands are niobium carbide. The dark dots are silicate inclusions in the matrix of cobalt-chromiu m solid solution. Electrolytic etch: 5% H 3 PO 4 . 500× Fig. 138 MAR-M 302, as-cast. Structure consists of primary, or eutectic, M 6 C particles (dark gray) and MC particles (small white crystals) in the matrix of cobalt-chromium-tungsten solid solution. See Fig. 139 for better resolution of constituents. Kalling's reagent. 100× Fig. 139 MAR-M 302, as-cast, at a higher magnification than Fig. 138 . The mottled gray islands are primary eutectic carbide; the light crystals are MC particles; the peppery constituent within grains of the matrix is M 23 C 6 . Kalling's reagent. 500× Fig. 140 MAR-M 509, as-cast. The structure consists of MC particles in script form and M 23 C 6 particles in eutectic form (gray areas) and precipitate form in the dendritic α solid-solution matrix (fcc). Kalling's reagent. 100× Fig. 141 Same as Fig. 140, but at a higher magnificatio n to reveal morphology of MC script particles, primary eutectic particles (M 23 C 6 ), and precipitated M 23 C 6 (shadowy constituent) in the α (fcc) matrix. Electrolytic etch: 5% H 3 PO 4 . 500× Fig. 142 MAR-M 509, aged at 705 °C (1300 °F), Thin-foil electron micrograph . Top left to bottom right: precipitated M 23 C 6 ; α(fcc) matrix; blocky M 23 C 6 with cobalt; cobalt with internal precipitate; lamellar M 23 C 6 in matrix. As-polished. 10,000× Aluminum Alloys: Metallographic Techniques and Microstructures Revised by Richard H. Stevens, Aluminum Company of America Introduction ALUMINUM ALLOYS encompass a wide range of chemical compositions and thus a wide range of hardnesses. Therefore, the techniques required for metallographic preparation and examination vary considerably. Softer alloys generally are more difficult to prepare by mechanical polishing, because (1) deformation caused by cutting and grinding extends to a greater depth, (2) the embedding of abrasive particles in the metal during polishing is more likely, and (3) relief between the matrix and second-phase particles, which are considerably harder than the matrix, develops more readily during polishing. Harder alloys, although easier to prepare, present a greater variety of phases and complexities of structure. However, methods exist for circumventing the difficulties of preparing and examining soft and hard alloys. Many methods are general and apply to all metals, but some have been developed specifically for aluminum alloys. Many recovery and precipitation processes in aluminum alloys can occur at relatively low temperatures, such as 150 to 250 °C (300 to 480 °F), which are readily produced in such operations as cutting, grinding, and mounting. These operations rarely produce changes visible by optical microscopy, although they may do so in extreme cases. However, they can produce changes in structure that are visible with an electron microscope. The metal must not overheat during specimen preparation: extra care must be taken when using unconventional methods or materials. Aluminum is a chemically active metal that derives its stability and corrosion resistance from a protective film of oxide that prevents as-polished and etched surfaces from deteriorating rapidly. Oxide films thicker than normal can be formed in a controlled manner by making the specimen the anode of an electrolytic cell. These films can be used to reveal microstructural features. When some types of anodic films are formed on a polished surface and when the surface is examined with reflected plane-polarized light passed through an analyzer, striking contrast effects are produced that reveal grain size and shape and orientation differences (Ref 1). Anodic film replicas have also proved useful in electron microscopy. Reference 1. P. Lacombe and M. Mouflard, "Les Applications de la Micrograph ie en Couleurs par Formation des Pellicules Minces Epitaxiques à Teintes d'interference à l'Ètude de l'Aluminium, du fer et du Cuivre," Editions Mètaux Saint Germain en Laye; extract from Mètaux (Corrosion Ind.), Vol 28 (No. 340), Dec 1953, p 471-488 Preparation for Macroscopic Examination Aluminum alloys require the same principles of preparation for macroscopic examination as most metals. Careful and thorough visual inspection of the part or shape to be examined should precede cutting or etching. Fracture surfaces should be carefully preserved to guard against abrasion or contamination. If the part is to be sectioned, selection of the cutting plane is determined by directionality or fibering due to the working process by which the part was formed, by the suspected or known form of defect, and by the general form or nature of the part (for example, casting, forging, extrusion, or weldment). Mechanical Preparation. The purpose of the examination and the type of etchant to be used determine the proper preparation of a cut surface for etching. Most macroetchants can reveal some details of macrostructure on a rough cut surface, but the overetching necessitated by the lack of initial smoothness can easily obscure significant details. Generally, a smoother or more highly polished surface requires less etching to reveal the same amount of gross detail; it also reduces the chance of losing fine detail. Machined surfaces frequently are acceptable for macroetching and examination. However, machining with a dull tool or at unfavorable speed and feed can distort the surface and misrepresent grain structure or degree of porosity. This is particularly important when using dye penetrant and developer for revealing density, shrinkage, or gas porosity in a cast material. A shaper or milling machine is preferred to a lathe, which does not provide a constant cutting speed on a flat surface. Chemical Preparation. Removal of cutting oils and other greasy contaminants from aluminum surfaces before etching is helpful, but not always necessary. Table 1 lists several etchants and etching methods that will adequately prepare specimens for macroexamination. Other combinations of concentration, proportions or dilution, temperature, and time often can be used without greatly altering the end effects. Table 1 Etchants for macroscopic examination of aluminum alloys See Table 2 for applicability to specific alloys Etchant Composition Procedure for use 1 (caustic etch) 10 g NaOH to each 90 mL H 2 O Immerse specimen 5-15 min in solution heated to 60-70 °C (140-160 °F) (a) , rinse in water, dip in 50% HNO 3 solution to desmut, rinse in water, dry. 2 (Tucker's reagent) 45 mL HCl (conc), 15 mL HNO 3 (conc), 15 mL HF (48%), 25 mL H 2 O Mix fresh before using. Immerse or swab specimen for 10-15 s, rinse in warm water, dry, and examine for desired effect. Repeat until desired effect is obtained. 3 1 mL HF (48%), 9 mL H 2 O Requires fairly smooth surface. Immerse until desired effect is obtained, hot water rinse, dry. 4 (Poulton's reagent) 12 mL HCl (conc), 6 mL HNO 3 (conc), 1 mL HF (48%), 1 mL H 2 O May be premixed and stored (b) for long periods. Etch by brief immersion or by swabbing. Rinse in cool water, and do not allow the etchant or the specimen to heat during etching. 5 50 mL HCl (conc), 15 mL HNO 3 (conc), 3 mL HF (48%), 5 mL FeCl 3 solution (conc) Mix fresh before using. Cool solution to 10-15 °C (50-60 °F) with jacket of cold water. Immerse a few seconds, rinse in cold water; repeat until desired effect is obtained. 6 10 mL HCl (conc), 30 mL HNO 3 (conc), 20 mL H 2 O, 5 g FeCl 3 Mix fresh before using. Add HCl last. Use at room temperature. Immerse a few seconds, rinse in cold water; repeat until desired effect is obtained. Can also use by swabbing. 7 60 mL HCl (conc), 40 mL HNO 3 (conc) Mix fresh before using. Immerse or swab for a few seconds, rinse in cold water, dry, examine. Repeat until desired effect is obtained. 8 20 g CuCl 2 (cupric chloride), 100 mL H 2 O Immerse specimen for a few seconds. Remove copper deposit with a mixture of 6 parts HNO 3 (conc) and 1 part HF (conc). Repeat until desired effect is obtained, cleaning with HNO 3 -HF mixture and rinsing in water between steps. (a) This etchant may be used without being heated, but etching action will be slower. (b) Solution should be stored in a vented container, preferably under a fume hood, to prevent buildup of gas pressure. The container should be made of polyethylene or be lined with wax. The caustic etch (etchant 1 in Table 1) is an excellent degreaser. The acidic etchants are more likely than the caustic etch to act unevenly if the surface is not precleaned. Thorough degreasing should precede dye penetrant testing. Before the dye penetrant is applied, a very light caustic etch (etchant 1 in Table 1) can be used to remove any minor sealing of porosity by smeared metal. These precautions ensure a surface free from smeared metal and are particularly important in evaluating direct-chill cast ingots, in which the dimensions of individual pores may be quite small. Customary safety precautions in handling strong reagents, including proper ventilation should always be observed. Etchant containers should be chosen for their resistance to reaction with hydrofluoric acid (HF) or caustic. Final rinsing in warm or hot tap water facilitates drying. Blowing dry with clear compressed air lessens the chances of staining. Preparation for Macroscopic Examination The optimum procedure for microscopic examination is determined using the same considerations as for macroscopic examination, although the area to be examined usually is smaller. Sectioning. Aluminum alloys can be sectioned by any standard cutting method; however, the cutting must not alter the structure or the configuration of the specimen in the plane to be examined. Because many aluminum alloys are soft, sawing or shearing should be done at a distance from the plane to be polished and then the intervening deformed material removed by wet grinding and polishing. An abrasive saw permits cutting closer to the plane of polishing. The temperature of the metal must not increase sufficiently during cutting to affect adversely the results of the examination. Because the grains in wrought aluminum alloys are rarely equiaxed, sections for determining grain size must be defined regarding the principal direction of working. Mounting in a plastic medium to form a cylindrical piece is the accepted procedure, unless the specimen is large enough to be hand held for subsequent grinding and polishing. Standard mounting materials and methods are described in the article "Mounting of Specimens" in this Volume. Special problems relating to the selection of mounting method or material may be caused by (1) inclusion of alloys of dissimilar hardnesses in the same mount, (2) the need to maintain flatness to the edge, (3) the need to mount thin sheet specimens for polishing in a plane perpendicular to the rolled surface, and (4) the need to connect electrical leads to one or more specimens for subsequent electropolishing or electrolytic etching. The mounting medium should not be so hard that it inhibits polishing of the softest aluminum contained in the mount or so soft that it allows rounding of the metal edges. Specimen edges whose flatness must be preserved should not be placed near the outer edge of the mounting ring. Thin sheet specimens can be bent or clamped in various ways, but it is most convenient to pack mount them by bolting layers together. The bolted pack can be mounted in plastic or cut to a convenient shape and size for polishing. If a bolt material other than an aluminum alloy is used, it should be coated or insulated before etching to prevent galvanic corrosion. Entrapment and seepage of liquid between layers can be minimized by immersing the pack mount in a bath of molten wax for a few minutes, removing it from the bath and cooling it until the wax has solidified, then wiping off the excess wax. Interleaving with a soft aluminum foil or thin sheet helps distinguish the interface between similar alloys, aids in revealing the thickness of anodic films, and minimizes entrapment and seepage of liquid between layers. Pack mounts are also convenient when multiple-sheet specimens are to be electropolished or electrolytically etched. Various methods are used for making electrical connections to metal mounted in plastic. One method is to make the mount electrically conductive by preparing it from an approximately equal mixture of plastic mounting powder with clean, dry aluminum chips from a band saw. When the heat or pressure of mounting must be avoided, various castable plastics can be used at room temperature. They can be used to fill in crevices and cracks by vacuum impregnation, even when thermal mounting is to be used. Grinding. Aluminum alloys can be ground using the same general techniques for all metals. Because aluminum alloys can be ground readily with various abrasives, selection is made on an individual basis. Generally, grinding is performed in successive steps using silicon carbide abrasive papers of 180, 220, 320, 400, and 600 grit. The starting grit size depends on the type of cut surface being removed. If the specimen has been cut with a hacksaw or band saw, 180- or 220-grit paper should be used. If the specimen has been cut with a jeweler's saw or a fine abrasive or diamond wheel, initial grinding can be performed using 320-, 400-, or 500-grit paper. Silicon carbide papers in grit sizes of 800 and 1000 are available from some suppliers; these are equivalent to 10 and 5 μm, respectively. Using 800- and 1000-grit silicon carbide papers, fine grinding can be achieved without using diamond abrasives. These finer grit sizes cause less surface deformation and produce a more uniform surface finish than diamond abrasives, thus facilitating subsequent polishings. If these papers are used, the number of grinding steps can often be reduced to five: 220, 400, 600, 800, then 1000 grit. Motor-driven belt grinders or disk-shaped laps hasten grinding, but care must be taken to prevent overheating of the specimen. Running water suffices as a coolant and lubricant at all stages when used with a water-resistant backing for abrasive materials. The specimen should be thoroughly washed after each grinding to prevent carryover of abrasive particles to the next stage. Abrasive particles embed easily into softer aluminum alloys. Therefore, kerosene, with or without dissolved paraffin, may be applied periodically to metallographic emery papers while hand grinding. During wet grindings with silicon carbide papers, however, less pressure should be applied to the specimen and adequate water should be used to flush away loose abrasive particles. Mechanical Polishing Mechanical polishing can be accomplished in two steps: rough and finish polishing. Rough polishing is performed using a suspension of 600-grit alumina (Al 2 O 3 ) powder in distilled water (50 g/500 mL H 2 O) on a billiard cloth fixed to a rotating wheel. Diamond abrasive of 6, 3, or 1 μm (depending on the final grinding step used) on a short-nap cloth disk can also be used. The 600-grit Al 2 O 3 is excellent for removing the thin layer of metal that smears over fine cracks and porosity during rough grinding; however, excessive time and pressure will result in rounded specimen edges and constituents in relief. These problems can be addressed with a subsequent step using 1-μm diamond on a short-nap cloth. The diamond can be applied as a paste or as spray and replenished as needed to provide continued cutting action. During diamond polishing, a lubricant of kerosene or a propylene glycol solution should be added to the rotating wheel. Propylene glycol solutions are the most commonly used lubricant. Considerable hand pressure is used initially, then gradually reduced. Wheel speeds of 500 to 700 rpm are typical. For rough polishing to be successful, polishing times should range from 1 to 2 min, and short-nap cloths should be used. Specimens should be thoroughly washed or ultrasonically cleaned to remove all abrasive after rough polishing. Final polishing of aluminum alloys is generally performed using a pure, heavy grade of magnesium oxide (MgO) powder with distilled or deionized water on a uniformly textured medium- or short-nap cloth. A suspension of silicon dioxide (SiO 2 ) in distilled water is also available commercially. This medium has a slightly basic pH and a grit size of 0.04 μm. An advantage of SiO 2 is its ability to remain in suspension; therefore, it can be purchased in the liquid form, then used without preparation. The same guidelines for cleanliness apply to SiO 2 as to MgO; the polishing cloth must be cleaned carefully immediately after each use to prevent the compound from hardening, thus rendering the polishing cloth ineffective. The mouth of the container in which the suspension of SiO 2 is stored should be wiped clean before pouring any material on the polishing cloth so that the hard particles that have formed around the mouth are not carried onto the cloth. The MgO should be kept in tight, dry containers. It can also be reclaimed by sifting through a 200-mesh screen or by baking for a few minutes at 800 to 1000 °C (1470 to 1830 °F). When final polishing with MgO, a teaspoon of the abrasive is applied near the center of the cloth, moistened with distilled or deionized water, then worked into a paste. A variable-speed wheel is preferred for final polishing; however, a two- speed wheel is satisfactory if the speeds are approximately 350 rpm or less. Considerable hand pressure and frequent rotation of the specimen are used for the first few minutes, and only enough water is added to avoid dryness and pulling of the specimen by the cloth. Gradually, pressure is reduced, and more water is added to wash away excess abrasive. Toward the end of the polish, copious water can be used to remove all abrasive, and the polishing cloth in effect wipes the specimen clean. [...]... 1100 0.12Cu-99.00Al (min) 1230 99.30Al (min) 2014 Al-0.8Si-4.4Cu-0.8Mn-0.5Mg 2024 Al-4.4Cu-0.6Mn-1.5Mg 2025 Al-0.8Si-4.5Cu-0.8Mn 2117 Al-2.6Cu-0.35Mg 22 18 Al-4.0Cu-1.5Mg-2.0Ni 2219 Al-6.3Cu-0.3Mn-0.06Ti-0.1V-0.18Zr 26 18 Al-2.3Cu-1.6Mg-1.0Ni-1.1Fe-0.07Ti 3003 Al-0.12Cu-1.2Mn 5052 Al-2.5Mg-0.25Cr 5 083 Al-0.6Mn-4.45Mg-0.15Cr 5 086 Al-0.45Mn-4.0Mg-0.15Cr 5454 Al-0.8Mn-2.7Mg-0.12Cr 5456 Al-0.8Mn-5.1Mg-0.12Cr... Al-0.3Mn-1.0Mg 5657 Al-0.8Mg 6061 Al-0.6Si-0.27Cu-1.0Mg-0.2Cr 6063 Al-0.4Si-0.7Mg 6151 Al-0.9Si-0.6Mg-0.25Cr 6351 Al-1.0Si-0.6Mn-0.6Mg 7004 Al-0.45Mn-1.5Mg-4.2Zn-0.15Zr 7039 Al-0.27Mn-2.8Mg-0.2Cr-4.0Zn 7072 Al-1.0Zn 7075 Al-1.6Cu-2.5Mg-0.3Cr-5.6Zn 7079 Al-0.6Cu-0.2Mn-3.3Mg-0.2Cr-4.3Zn 71 78 Al-2.0Cu-2.7Mg-0.3Cr-6.8Zn Aluminum casting alloys(b) 201 (KO-1) Al-4.7Cu-0.6Ag-0.3Mg-0.2Ti 222 (122) Al-10.0Cu-0.2Mg... .) Al-5.0Cu-0.4Mn 2 38 (1 38) Al-10.0Cu-4.0Si-0.3Mg A240 (A140) Al -8 . 0Cu-0.5Mn-6.0Mg-0.5Ni 242 (142) Al-4.0Cu-1.5Mg-2.0Ni 295 (195) Al-4.5Cu-0.8Si 3 08 (A1 08) Al-4.5Cu-5.5Si 319 (319) Al-3.5Cu-6.0Si A332 (A132) Al-12.0Si-0.8Cu-1.2Mg-2.5Ni 354 (354) Al-9.0Si-1.8Cu-0.5Mg 355 (355) Al-1.3Cu-5.0Si-0.5Mg 356 (356) Al-7.0Si-0.3Mg A356 (A356) Al-7.0Si-0.3Mg-0.2Fe max A357 (A357) Al-7.0Si-0.5Mg-0.15Ti 380 ( 380 )... Al-9.0Si-3.5Cu 384 ( 384 ) Al-12.0Si-3.8Cu 392 (392) Al-19.0Si-0.6Cu-0.4Mn-1.0Mg 413 (13) Al-12.0Si 443 (43) Al-5.0Si B443 (43) Al-5.0Si-0.3Cu max C443 (A43) Al-5.0Si-2.0Fe max 520 (220) Al-10.0Mg D712 (D612, 40E) Al-0.6Mg-5.3Zn-0.5Cr 85 0 (750) Al-1.0Cu-1.0Ni-6.5Sn Aluminum alloy filler metals and brazing alloys ER2319 Al-6.2Cu-0.30Mn-0.15Ti ER4043 Al-5.2Si ER5356 Al-0.12Mn-5.0Mg-0.12Cr-0.13Ti 5456 Al-0.8Mn-5.1Mg-0.12Cr... Al-Cu-Fe-Si-Mg-Mn 2014 2024 Al-Cu-Mg-Ni-Fe-Si 22 18, 26 18 Ingot and wrought In addition to others, nickel may cause NiAl3, Ni2Al3, Cu3NiAl6 or FeNiAl9 to appear Al-Fe-Mg-Si-Mn-Cr 5 083 ,5 086 ,5456 Ingot (Fe,Mn,Cr)Al6, (Fe,Mn,Cr)3SiAl12, Mg2Al3, (Cr,Mn,Fe)Al7(b) Wrought (Fe,Mn,Cr)3SiAl12, Mg2Si, Mg2Al3, Cr2Mg3Al 18( a) 7075 Ingot (Fe,Cr)Al3, (Fe,Cr)3SiAl12, Mg2Si, Mg(Zn2AlCu), CrAl7(b) Wrought Al-Cu-Mg-Zn-Fe-Si-Cr... of alloy Alloy form Phases Al-Fe-Si 1100, EC Ingot FeAl3, FeAl6, Fe3SiAl12, Fe2Si2Al9, Si Wrought FeAl3, Fe3SiAl12 Ingot (Fe,Mn) Al6, α(Al-Fe,Mn-Si), Si Wrought (Fe,Mn) Al6, α(Al-Fe,Mn-Si) Ingot FeAl3, FeAl6, Fe3SiAl12, Mg2Si Wrought FeAl3, Fe3SiAl12, Mg2Si Al-Fe-Mn-Si Al-Fe-Mg-Si (Mg: Si ; 1.7:1) 3003 6063 Al-Fe-Mg-Si (high silicon) 356 Cast Fe2Si2Al9, Mg2Si, Si Al-Fe-Mg-Si (high magnesium) 520 Cast... High-purity aluminum 4 or 5 Commercial-purity aluminum: 1xxx series 1, 2, or 4 All high-copper alloys: 1, 6, or 7 2xxx series and casting alloys Al-Mn alloys: 3xxx series 1, 2, 4, or 6 Al-Si alloys: 4xxx series and casting alloys(a) 2, 3, 4, or 8 Al-Mg alloys: 5xxx series and casting alloys 1, 2, 4, or 6 Al-Mg-Si alloys: 6xxx series and casting alloys 1, 2, 4, or 6 Al-Cu-Mg-Zn alloys: 7xxx series and. .. Fe3SiAl12 and Si Moderate; light to dark gray Etchant 1 (immerse) will attack and darken to varying degrees, depending on ironsilicon ratio Etchant 7 will attack and dissolve it out In both cases, Fe3SiAl12 is outlined but not appreciably darkened Mg3Zn3Al2 or T (Al-Mg-Zn) (See CuMg4Al5) Mn3SiAl12 or α(Al-Mn-Si) (See Fe3SiAl12)(g) Cu2Mg8Si6Al5 or Q (Al-Cu-Mg-Si), λ(Al-Cu-Mg-Si), h (Al-Cu-Mg-Si) This... Al-0.12Mn-5.0Mg-0.12Cr-0.13Ti 5456 Al-0.8Mn-5.1Mg-0.12Cr R-SG70A Al-7Si-0.30Mg 4047 (BAlSi-4) Al-12Si 4245 Al-10Si-4Cu-10Zn 4343 (BAlSi-2) Al-7.5Si No 12 brazing sheet 3003 alloy, 4343 cladding on both sides (a) Wrought alloys are identified by Aluminum Association designations (b) Casting alloys are identified first by Aluminum Association designations (without decimal suffixes) and then, parenthetically, by... alloys 8 (1 min) Rosettes and grain-boundary eutectic 6xxx series alloys 2 Grain-boundary eutectic formations 7xxx series alloys 3B Rosettes and grain-boundary eutectic formations Examination for general constituent size and distribution All wrought alloys and casting alloys 1, 8, 15 (1 min) or any etchant that does not pit solid-solution matrix Coarse insoluble particles and fine precipitate particles . Mg 3 Zn 3 Al 2 or T (Al-Mg-Zn) (See CuMg 4 Al 5 ) Mn 3 SiAl 12 or α(Al-Mn-Si) (See Fe 3 SiAl 12 ) (g) Cu 2 Mg 8 Si 6 Al 5 or Q (Al-Cu-Mg-Si), λ(Al-Cu-Mg-Si), h (Al-Cu-Mg-Si) . . . This. Etchant 8 (1 min) does not attack it, but the color distinction between it and CuAl 2 remains the same as when not etched. FeMg 3 Si 6 Al 8 or Q (Al-Fe-Mg-Si), π(Al-Fe-Mg-Si), h (Al-Fe-Mg-Si). 32 0-, 40 0-, or 500-grit paper. Silicon carbide papers in grit sizes of 80 0 and 1000 are available from some suppliers; these are equivalent to 10 and 5 μm, respectively. Using 80 0- and 1000-grit