Research Metallograph

Research Metallograph

Metallurgy

Physical Description

The metallograph sits atop a metal desk to which its frame is attached with two steel rods. The desk, which was sold with the instrument, contains shock-absorbing pillars that allow imaging in settings where mechanical vibrations may cause issues.

The instrument is comprised of three separate components (from left to right): camera, microscope, and illuminator. The camera slides along a steel beam and is fixed with clamping screws at the front and rear. Two rotating metal rods below the camera allow for fine focusing. The microscope has numerous dials and controls: centering screws, duplicate controls, aperture handle, field diaphragm ring, dark field handle, axis selector lever, coarse adjustment handle, and fine adjustment knob. These are used to center the stage’s axis of rotation, move the sample stage on a horizontal plane, adjust the aperture or field diaphragms, switch between bright and dark field imaging, change direction of light from microscope to camera, rapidly adjust the sample stage vertically, and finely adjust the sample stage vertically respectively.

The monocular microscope body is interchangeable for lenses of other powers and can be easily removed from its holder. A portion of the sample stage can also be lifted to change between objective lenses. Lenses provided with the machine range from 25X to 1500X magnification (“Balphot Metallograph” 1962), with different combinations of monocular and objective lens magnifications determining the final magnification.

The illuminator uses a threaded-based zirconium oxide bulb, a light source with a small area, high brilliance, and long lifespan (“Balphot Metallograph” 1962). This type of light source is considered optimal for color photomicrography and requires no adjustments during operation.

Functional Description

The metallograph is primarily used with bright field illumination (i.e., unfiltered light reflected off the sample). The user ensures that all filters, polarizers, or other apparatus do not impede the light from the illuminator and centers the aperture diaphragm. They bring the stage into the focus position and remove the sample stage to attach the objective lens with the desired power. They then reattach and center the stage and clamp the sample on the stage.

With the desired eyepiece in the microscope body, they set the axis selector lever to “Micro”, which directs reflected light from the sample to the monocular eyepiece. They then use the fine adjustment knob to bring the image into sharp focus and apply filters or adjust the aperture and field diaphragms to yield a desired image (“Balphot Metallograph” 1962). They then can then also divert the reflected light to the camera, recording the image on a ground glass plate negative. Imaging may also require some focusing as it is in a different light path by sliding the large end of the camera until the picture becomes clear and then adjusting the fine focus. Exposure time of this fixed-aperture camera is set with a curled ring and the shutter released with a mechanical cable release (“Balphot Metallograph” 1962).

Cody Durecka

1950s – 1970s

physical object

English

Overall: 174 cm long, 50 cm tall, 32 cm wide
Camera: 102 cm long, 50cm tall, 31 cm side length for larger square, 17 cm for shorter square,
Microscope: 29 cm long, 43 cm tall, 32 cm wide
Sample Platform: 18 cm diameter with 7.6 cm stabilizing pin
Illuminator:37 cm long, 50 cm tall, 11 cm wide

steel, glass, bakelite

Bausch & Lomb, Rochester, NY

The microscope section is inscribed with "ONE DIV.=0.002mm SERIAL NO.FE537" with the Bausch and Lomb logo on the Camera and Illuminator sections and the Bausch and Lomb stamp on the Camera section.

It is not clear exactly when the metallograph came to Michigan Tech or the Materials Science and Engineering (MSE) department. The department received a manual for a similar instrument (a “Balphot metallograph”) on June 15, 1962, which may indicate that this slightly older instrument came to us from other institutions, as was common among research laboratories in the mid-twentieth century.
The first metallographic microscope was invented in 1863 by Henry Clifton Sorby to analyze the content of metals and meteorites (Clinging 2012). His invention used a tiny plane mirror to direct perfectly vertical light to the specimen (Humphries 1973). This instrument was the first able to visualize the carbon content and the microstructures (metallic “phases”) that relate to the steel’s strength (Humphries 1973). Subsequently, many different companies and inventors designed different microscopes to better analyze the microstructure of different materials using different techniques.
The research metallograph, created and marketed by Bausch and Lomb (B+L) in the late 1940s, is a considerable improvement from Sorby’s original design and was very different from B+L’s previous designs. The original B+L microscope designs used brass barrel objectives, were smaller in size, and designed for use across multiple fields (del Cerro 2007). Older designs also lacked attached illuminators and anti-reflective coatings on the optics (del Cerro 2007).
The research metallograph included adjustments for light intensity, filters, apertures, and diaphragms, coated objective lenses to reduce glare and improve imaging, and an integral view camera on rails (the main draw of the instrument). Certain design elements, like the brass objectives, were eliminated to market the instrument as “modern.” While no information about a specific inventor exists, the B+L version of the instrument was one of the most widely used versions of the instrument from the 1950s through the 1970s (Roman 1964; Hopkins 1962; Grey, Long, and Richt 1970; Pound, Madonna, and Peake 1953), though other companies did make similar products (LaRocca 1955).

M&M building, canal side, 5th floor hallway, southeast corner

“Balphot Metallograph reference manual,” 1962. Bausch and Lomb Inc. [Thanks to Vademecum Microscopes page of old B&L manuals]

Cerro, Manuel del. 2007. “Mic-UK: The Rise and Fall of the Bausch & Lomb Research Microscope DDE.” Microscopy UK. 2007.

Clinging, Valerie. 2012. “A Biography of Henry Clifton Sorby.” Henry Clifton Sorby: Sheffield’s Greatest Scientist. February 5, 2012.

Grey, R, E Long, and A Richt. 1970. “Metallography of Radioactive Materials at Oak Ridge National Laboratory.” Applications of Modern Metallographic Techniques, 67–96.

Hopkins, E. 1962. “Thirty-Five Millimeter Color Photomicrography.” Technical Papers of the Sixteenth Metallographic Group Meeting, Held March 28-29, 1962 at Hanford Atomic Products Operation, Richland, Washington, 14–19.

Humphries, Derek William. 1973. “The Contribution of Henry Clifton Sorby (1826—1908) to Mineral Science and Technology.” Mineralia Slovaca 5 (4): 593–601.

LaRocca, E. 1955. “Adaptation of Bergsman Microhardness Tester to American Optical Metallograph.” Journal of the Optical Society of America and Review of Scientific Instruments 26 (6): 590–91. 

Pound, G. M, L. A Madonna, and S. L Peake. 1953. “Critical Supercooling of Pure Water Droplets by a New Microscopic Technique.” Journal of Colloid Science 8 (2): 187–93. DOI:10.1016/0095-8522(53)90037-3.

Roman, H.R. 1964. “Technical Papers of the Sixteenth Metallographic Group Meeting, Held March 28-29, 1962 at Hanford Atomic Products Operation, Richland, Washington.” NMI-4998, CONF-620301, 4627304. DOI:10.2172/4627304.