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Ti-4Zr, as cast and annealed at 800C, air cool, mod. Weck’s reagent, XPST, 100x

17-4 PH SS, solution annealed and aged (martensite), containing delta ferrite which was colored using Murakami’s reagent at 100C, 200x, BF

316 austenitic stainless steel, containing sigma phase (formed probably from delta ferrite after low-time, high-temperature exposure) colored by Murakami’s reagent at 80C, 500x, BF

Alloy 600 Inconel from the center of a large forging, as-forged. It was etched with glyceregia and is 200x, BF

As-cast electron beam melted an Inconel alloy 718, Beraha’s BIII etch, 50x

AF1410, ultra-high strength steel, austenitized at 1600F, WQ, aged at 1200F for 8 h (basically an “anneal” for machining), etched with 10% sodium metabisulfite in water, 100x, polarized light (XP) and sensitive tint (ST). The structure is lath martensite.

Carpenter’s AerMet 100, an offshoot of AF1410, over-austenitized at 1850F (coarsen the grain size so you can see the lath martensite better), AQ, 1200F temper, also 10% SMB, 200x, XP+ST.

Commercial purity Ti, ASTM F67, Grade 2, in the as-rolled condition, in polarized light after polishing (finish with vibratory polisher).

This image is of a SCC crack in 4340 alloy steel etched at 80C with aqueous saturated picric acid, plus ~0.5% HCl and a wetting agent to reveal the prior austenite grin boundaries, 500x, BF. The steel was at about 38HRC (tempered martensite) in salt water, which is too high a strength to avoid SCC in this environment. (Stress Corrosion Crack - SCC)

As cast Ti-6Al-4V, etched with mod. Weck’s reagent

Near-beta alloy, Ti – 5% Al – 5% Mo – 5% V – 3% Cr – 0.5% Fe (called Ti5553). Etched with modified Weck’s reagent and taken at 50 x using polarized light and sensitive tint.

Same as above except stabilization of alpha phase at the surface due possibly to oxygen pick-up.

Inconel X750, solution annealed and aged, glyceregia etch, 100x.

Duplex stainless steel, Carpenter’s 7 Mo Plus, with the ferrite colored (austenite white, unaffected), etched with Beraha’s BI reagent, in bright field.

Waspaloy in the solution annealed and double aged condition, etched with Beraha’s B4 (BIV), in bright field.

Photo Credits: Many of the photomicrographs taken by George F. Vander Voort, Buehler Ltd.


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