Page 98 - MSAM-4-2

Materials Science in Additive Manufacturing Additively manufactured high carbon steel

A B

C

D

Figure 2. Macrostructural characteristics of the as-printed samples. (A) X-ray diffraction patterns of the as-printed sample and the sample quenched in
LN for 2.5 h. (B-D) Electron micrographs of the as-printed (B) and quenched samples (C and D)
2
surface undulations from the displacive movements of the martensitic or ferritic peak was noticeably less dominant
martensitic transformation after cryogenic quench were compared to the 950°C solutionizing temperature.
visible. Since no reconstructive phase transformation has Particularly for the 1075°C anneal, the dominant austenitic
occurred, the backscatter electron (BSE) micrograph of peak is approximated to be 45 vol.%.
the quenched sample in Figure 2D demonstrated that the Findings from XRD were confirmed by electron
cellular dendrites from the rapid solidification process still micrographs presented in Figure 4. The as-printed
decorate the microstructure, which can be dissolved by microstructure in Figure 4A is primarily austenitic,
solutionizing treatment.
decorated by fine cellular dendrites with some martensite
3.2. Solutionizing treatment growing across multiple cells. After solutionizing at
950°C for 1 h, the cellular microstructure was replaced by
Figure 3 compares the XRD patterns from the as-printed carbides nucleated within and along the grain boundaries.
sample and those solutionized at 950, 1050, and 1075°C These carbides are predicted to be M C according to
for 1 h. The as-printed sample consisted primarily of thermodynamic calculations presented in Figure 1B.
7
3
austenite with peaks observed at 43.3°, 50.4°, and 73.9°.
When solutionized at 950°C for 1 h, the now convoluted No cells were observed within the matrix, which indicates
γ(111) peak exhibited a slight shift to a higher 2θ, with a that the solutionizing treatment at this temperature is
more dominant peak appearing roughly at the 2θ position sufficient for the dissolution of cells. Although the sample
for martensite, which accounted for approximately 90 was immediately quenched in water, partial formation of
vol.%. The rightward shift is most likely due to the outward martensite or Widmanstätten ferrite within the austenite
diffusion of C and Cr from the supersaturated matrix to grains was observed. The microstructure of the sample
form carbides. When solutionized at 1050 and 1075°C, solutionized at 1050°C for 1 h also highlights the dissolution
the austenitic peak was pronounced, and the convoluted of cells; however, the number of carbides observed is much

Volume 4 Issue 2 (2025) 5 doi: 10.36922/MSAM025100011