#pearlite

ankur/ankurous/ankurousity - an ankuragender gender quality; a gender quality that feels as if it is hooking the entire identity together or is an “anchor” inside of the identity; a gender quality that feels particularly drawn to the sea & can be connected to the ocean, dark waters, boats sailing from a harbor, lighthouses during a hurricane, hurricanes, cold waters, & seaside villages.

ancoralis | anchora | ancora

ancoralis - a term for an older ankuragender individual.

anchora - a term for an ankuragender individual regardless of age.

ancora - a term for a younger ankuragender individual.

pearle | pearlite

pearle - a term for an ankuragender partner.

pearlite - a term for an ankuragender spouse.

symbols from photopea.

Fe, C 0.8 (wt%) steel, eutectoid transformation, normalised at 900ºC

Processing Normalised 900 ºC [...] Sample preparation Nital Technique Reflected light microscopy Length bar 400 μm / 100 µm Further information This steel is of the eutectoid composition. Once the temperature is lowered below the eutectoid temperature the steel becomes simultaneously supersaturated with both ferrite and cementite. A eutectoid transformation results (g to a + Fe3C). The resultant microstructure, known as pearlite, comprises lamellae of cementite (dark) embedded in ferrite (white). The platelets are parallel to each other and do not follow a specific crystallographic direction. Contributor Dr R F Cochrane Organisation Department of Materials, University of Leeds

Fe, C 0.8 (wt%), eutectoid transformation - pearlite (coarse)

Processing Slow cooled [...] Technique Reflected light microscopy Length bar 200 μm / 80 µm / 40 µm Further information This steel is of the eutectoid composition. Once the temperature is lowered below the eutectoid temperature the steel becomes simultaneously supersaturated with both ferrite and cementite. A eutectoid transformation results (g to a + Fe3C). The resultant microstructure, known as pearlite, comprises lamellae of cementite (dark) embedded in ferrite (white). The platelets are parallel to each other and do not follow a specific crystallographic direction. Each pearlite colony is made up of a number of subgrains. Thus each pearlite colony consists of two interpenetrating single crystals having an orientation relationship with respect to each other and with respect to the austenite grain they grow from, but not with respect to the austenite grain they have grown into. Changes in the apparent interlamellar spacing from colony to colony in the photograph are due to differences in the lamellae spacing with respect to the polished surface. The coarseness of the pearlite is determined by the interlamellar spacing. This spacing is inversely proportional to the undercooling. This is primarily because of the increased rate of carbide nucleation with increased undercooling. The pearlite in this sample is coarse due to it being slowly cooled. The undercooling is low so the lamellae spacing is relatively large resulting in a coarse microstructure. [...] Organisation Department of Materials Science and Metallurgy, University of Cambridge

Fe, C 1.0 (wt%), hypereutectoid alloy

Processing: Normalised [...] Sample preparation: Etched in 3% nital Technique: Reflected light microscopy /  Scanning electron microscopy (SEM) Length bar: 400 μm / 40 µm / 50 µm / 10 µm Further information: This is a hypereutectoid alloy and illustrates the effect of a fast cooling rate on the resultant microstructure. The first phase to form from the austenite is proeutectoid cementite. With faster cooling there is less time for carbon to diffuse and the microstructure is more refined and  may form the initial cementite as Widmanstätten side plates. / This secondary electron SEM image shows the cementite delineating prior austenite grain boundaries with a thin layer. The amount of proeutectoid phase is very low, with the majority of the area being taken by the pearlite eutectoid. Again each pearlite cell has a different orientation with the ferrite phase being selectively etched. Contributor: Prof T W Clyne Organisation: Department of Materials Science and Metallurgy, University of Cambridge 

Fe, C 0.1 (wt%), hypoeutectoid alloy

Composition: Fe, C 0.1 (wt%) [...] Processing: Normalised [...] Sample preparation: Etched in 3% nital Technique: Reflected light microscopy  Length bar: 400 μm / 40 µm Further information: This is a hypoeutectoid alloy, which has been air cooled from the austenite phase field at 950 °C. The first solid to form is proeutectoid ferrite, its morphology being determined by the cooling rate. At slow cooling rates (furnace cooling) there is sufficient time for the carbon rejected from the austenite to diffuse and equilibrium solidification occurs. With faster cooling the microstructure also depends on the original austenite grain size. Fast cooling and large grain size favours ferrite forming as Widmanstätten side plates from the grain boundaries. Small grain sizes imply a high number of nuclei and hence the ferrite grows as grain boundary allotriomorphs. In this case air cooling is sufficiently slow to produce allotriomorphic ferrite. The majority of the austenite has changed to ferrite leaving only a small amount to be transformed to pearlite, therefore the microstructure shows large ferrite grains with small islands of pearlite.

Contributor Prof T W Clyne Organisation Department of Materials Science and Metallurgy, University of Cambridge

Sources: ( 1 ) ( 2 )

Technique: Scanning electron microscopy (SEM) Length bar: 30 µm / 10 µm Further information: This SEM image shows that the ferrite phase in the pearlite has been selectively etched compared to the cementite. The cementite phase appears to protrude from the surface. Within the pearlite region there are several colonies in different orientations, indicating that the pearlite nucleated on grains of the primary ferrite. / This SEM image of a pearlite region in the microstructure shown in micrograph no 19 shows that the ferrite phase in the pearlite has been selectively etched compared to the cementite. The cementite phase appears to protrude from the surface.  Within such A pearlite region there are several colonies in different orientations, indicating that the pearlite nucleated on grains of the primary ferrite. 

Normalised carbon steel

System: Fe-C-X

Composition: Fe, C 0.08 (wt%)

[...]

Processing: Normalised

[...]

Sample preparation: Nital

Technique: Reflected light microscopy

Length bar: 200µm / 400 μm

Further information: Low carbon steel with a microstructure consisting mostly of ferrite with the darker pearlite regions around the ferrite grains. Upon cooling the steel the ferrite forms initially, either on austenite grain boundaries or inclusions. This causes carbon to be partitioned into the austenite. Eventually the remaining austenite will be at the eutectoid condition and the transformation to pearlite will then take place. Micrograph was taken transverse to direction of casting, therefore no directionality is seen.

Contributor: Dr R F Cochrane

Organisation: Department of Materials, University of Leeds