2.2 CW511L, round bar, d=20 mm

2.2 CW511L, round bar, d=20 mm

Nordic Brass GUSUM CW511L is a lead free (Pb<0.1%), free cutting and forging brass in the form of rod. The alloy has very good dezincification resistance. It is approved according to the 4MS list, use for drinking water applications, product groups B-D. The structure is mainly α, but some β-phase may occur.  Applications: Fitting parts in contact with water where there are stringent requirements for dezincification resistance. The alloy comes with Aqua Nordic addition for improved machining properties to compensate for lead in traditional free cutting brass with high content of lead, like CW614N. Typical yield/tensile strength (MPa) 130/330. Elongation A50 >40%. Hardness (HRB) ~ 90. Information from Nordic Brass Gusum data sheet. The material was produced by Nordic Brass Gusum.

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    2.2.1 Light microscope images

    Material condition: M – As manufactured (extrusion), without specified mechanical properties

    CW511L, 100x Magnification CW511L, 100x Magnification
    CW511L, 200x Magnification CW511L, 200x Magnification
    CW511L, 500x Magnification CW511L, 500x Magnification

    Images of etched specimen at 100, 200 and 500 times magnification. Single phase brass microstructure with grains aligned in the ED. Some grains etch more than others, this is due to crystallographic orientations. The <100>//ED (compare to EBSD results) seem to etch less compared to other orientations. Lead particles in streaks along the ED.
    Etching: 5g ferric chloride + 10ml conc. hydrochloric acid + 100 ml
    de-ionised water. Specimen surface was parallel with extrusion

    direction (X=ED). Position ¼ depth.

    Composition of CW511L Composition of CW511L

    2.2.2 EBSD/EDS analysis in the SEM



    EBSD analysis with 1 µm step size

    The material show a microstructure consisting of mainly alpha phase. In this limited area it is difficult to make assumptions about grain sizes, phase fractions and texture.

    Specimen surface was parallel with extrusion direction (X=ED). Position ¼ depth. Surface was OP-S-polished.

    FSD image of the area for EBSD analysis. Streaks of particles along ED is seen, in spite of the low Pb content.
    IPF-Z EBSD map with colours according to crystal orientations in Z direction (transverse dir.).
    EBSD phase map, alpha phase is red and in this alloy beta phase is not present. Grain boundaries (>15deg) and low angle boundaries (2-15deg) are included.
    EBSD map show IPF in X direction (extrusion dir.).

    Grain- and phase boundaries

    This material is a single phase brass (alpha-brass).

    In this material there are not a lot of low angle boundaries and the twin boundaries look complete and straight. The assumption would be that recrystallisation occurred after extrusion.

    Grain boundaries (>15) are black.
Low angle boundaries (2-15) are grey.
Twin boundaries (60<111>) are red. Grain boundaries (>15) are black. Low angle boundaries (2-15) are grey. Twin boundaries (60<111>) are red.

    EDS mapping in parallel to EBSD analysis

    Some segregation of Cu/Zn is seen but almost no Beta phase was found in the microstructure. Pb particles in streaks, the variation between low and high Zn level was about 33-36%. Small Fe particles could be detected as well, but P, As, Bi etc. was not detected which indicates low levels and very small particles if present.

    Large area mapping – Many (>40) analyses stitched together

    The large area make statistics for grain size, phase fractions, texture, etc. better and now it is obvious that there ARE preferred orientations in X (ED). The pole figures show that there are actually preferred orientations (or texture), strong <100> and weaker <111> and <110> in ED. Some beta phase was found in streaks, but only VERY little, 0.01%.

    Alpha texture: 
22 times random Alpha texture: <100>//ED 22 times random

    Grain size, area weighted distribution