Microstructure of Historical Objects – Copper-Based Alloys

George’s Rules for Pain-free Specimen Preparation

  • Use gentlest possible sectioning equipment: abrasive cut off saw or precision saw
  • Use blades developed for metallography, not for production cutting
  • Avoid shrinkage gaps when mounting
  • Start grinding with the finest possible abrasive
  • Keep the polishing surface uniformly covered with abrasive and lubricant
  • Use proper loads

DOWNLOAD THE PRESENTATION HERE

Last Updated on Saturday, 09 February 2013 14:55

Hits: 986

Read more: Microstructure of Historical Objects – Copper-Based Alloys

Microstructure of Historical Iron-Based Objects

Abstract

The study of historical metallic objects is greatly aided by a careful metallographic examination. In many cases, the objects have undergone serious corrosion over the years and the corrosion product must also be examined. Generally, this dictates encapsulation in a good epoxy mounting material. Specimen preparation is the same as for contemporary irons and steels, and the same etchants are used. This paper presents results obtained when a number of iron-based objects were studied. Color tint etchants are particularly useful in this work as they are more selective in nature, reveal the grain structure fully, while revealing crystallographic texture, if present, and are better for revealing chemical inhomogeniety and residual deformation than standard black and white etchants.

DOWNLOAD THE PAPER HERE

Last Updated on Saturday, 09 February 2013 14:53

Hits: 973

Read more: Microstructure of Historical Iron-Based Objects

Characterizing Iron Based Historical Specimens - Buehler

Roman Nail, Broken below Head, Found in Vicenza, Italy - Montage of the broken Roman nail (left, Klemm’s I) and view of a typical large slag stringer (2% nital).

Patches of as-quenched martensite were found in the carburized nail head. Picral will not etch as-quenched martensite, but it will etch tempered martensite.
Patches of as-quenched martensite within the pearlitic carburized head revealed using 10% sodium metabisulfite.
Most of the head, but not in the center of the top face, was carburized. Etched with Beraha’s sulfamic acid 3/1 reagent (left) and Klemm’s I (right) and imaged with polarized light and sensitive tint.
Montage of the microstructure starting from under the head at the left corner (C –carburized) and going inward at the top of the shaft (AF –acicular ferrite; S –slag; EF –equiaxed ferrite). Klemm’s I, polarized light and sensitive tint used to image the structure.
Microstructure in the shaft (left, center and right side, respectively) revealing numerous mechanical twins (Neumann Bands) and slag stringers in a ferritic matrix. Beraha’s sulfamic acid (3/1) solution used with polarized light and sensitive tint to image the microstructure.
Higher magnification view of the mechanical twins in the ferrite in the shaft above the break (Beraha’s 3/1 sulfamic acid reagent, XP+ST).

DOWNLOAD THE PRESENTATION HERE

Last Updated on Saturday, 09 February 2013 14:51

Hits: 976

Read more: Characterizing Iron Based Historical Specimens - Buehler

Characterizing Iron Based Historical Specimens - Struers

George’s Rules for Pain-free Specimen Preparation

  • Use the gentlest possible sectioning equipment: abrasive cut off saw or precision saw only
  • Use blades developed for metallography, not for production cutting
  • Avoid shrinkage gaps when mounting
  • Start grinding with the finest possible abrasive
  • Keep the polishing surface uniformly covered with abrasive and lubricant
  • Use proper loads

Revealing the Microstructure

  • Nital and picralare good to assess the general structure
  • Selective etchants are excellent for phase identification and measurements, e.g., alkaline sodium picrate to color cementite
  • Prior-austenite grain boundaries in martensite can be revealed using aqueous saturated picric acid plus HCland a wetting agent at 80-90°C
  • Color “tint” etchants reveal details about grain orientation, chemical segregation and residual deformation and are phase specific
  • Choose the best illumination mode, e.g., dark field to reveal grain boundaries, polarized light for inclusions, and NomarskiDIC to reveal height differences between constituents that polish at different rates.

DOWNLOAD THE PRESENTATION HERE

Last Updated on Saturday, 09 February 2013 14:45

Hits: 958

Read more: Characterizing Iron Based Historical Specimens - Struers

resourcesThe articles and presentations that can be down-loaded from this web site are based upon work done by GFV while employed at Bethlehem Steel (1967-1983), Carpenter Technology (1983-1996), Buehler Ltd. (1996-2009) and Struers (2009-Present) and from the authors consulting work for companies such as, Latrobe Steel, Scot Forge, etc., and from his litigation work. GFV's bylined articles appearing in various issues of the ASM Handbook series have been listed here courtesy of ASM International, Materials Park, Ohio.

Log in to your account or