The Aluminum-Silicon Phase Diagram and Eutectic Modifications
The Aluminum-Silicon Phase Diagram and Eutectic Modifications
The Aluminum-Silicon Phase Diagram and Eutectic Modifications
Preparation of Pb, Pb-Sn and Sn-based Alloys
Preparation of Composites with Al Matrix
Picric acid (2,4,6-trinitrophenol, [(NO2)3C6H2OH]) is widely used in metallography labs for the common steel etchants known as picral, a 4% solution in ethanol, Vilella’s reagent, 1 g picric acid and 5 mL HCl and 100 mL ethanol, and alkaline sodium picrate (2 g picric acid, 20 g NaOH, 100 mL water) for coloring M3C and M6C carbides, as well as several other formulations. Picric acid was formulated by Peter Woulfe, a British chemist, in 1771, although Glauber is claimed to have written about it in 1742. The name comes from the Greek word pikros which means bitter, as picric acid has a bitter taste (it is toxic). Initially it was used to dye fabrics yellow. In the early 20th century, workers producing picric acid were sometimes called canaries, because their skin also became stained yellow
High-purity Pb and Sn are very difficult metallographic subjects and the alloys of Pb and Sn are somewhat easier to prepare, but still rather difficult. This Poster lists our preferred preparation procedure. Vibratory polishing is essential for best results. Pollack’s reagent (100 mLwater, 10 g citric acid, 10 g ammonium molybdate) is one of the best etchants for Pband Pb-Snalloys; 2% nitalis a good etch for pure tin..
Preparation of Pb, Pb-Sn and Sn-based Alloys
ABSTRACT
A three-step preparation procedure was developed for titanium and its alloys. Attack polishing is utilized in the third step for optimal results, particularly for imaging alpha-Ti with polarized light. Two-phase α-β alloy specimens and all β alloys are easier to prepare than single-phase α specimens. Kroll’s reagent appears to be adequate for most alloys. A modification of Weck’s reagent was used for color metallography.
Sand Cast Alloys
Microstructure of sand-cast AZ91D (Mg – 9% Al – 0.25% Mn – 0.7% Zn – 0.0008% Be) revealed (left) using the glycol etch and viewing with polarized light plus a sensitive tint filter; and (right) after etching with the acetic-glycol reagent and viewing in bright field illumination. The magnification bars are 100 and 50 μm, left and right, respectively. Note the mechanical twins at the surface.
Native Copper – Microstructure of native copper (112 HV). Note the extensive slip lines. Color micrograph was taken with crossed polarized light plus sensitive tint.
High-Purity Copper (99.89%) – Microstructure of hot extruded, cold worked and annealed (500 °C) high-purity copper etched with equal parts ammonium hydroxide and hydrogen peroxide (3% conc), 46 HV.
High-Purity Copper (99.89%) – Microstructure of hot extruded, cold worked and annealed (500 °C) high-purity copper etched with klemms III and Beraha’s PbS tint etches and viewed with polarized light plus sensitive tint, 46 HV.
GENERAL SUGGESTIONS ON PREPARATION METHODS