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Materials Science in Additive Manufacturing AM-produced CoCrFeMnNi properties

texture with a strong <100> alignment in all four samples. treatment led to increase in average grain size. However,
However, HT samples appear to have a stronger texture such increase is more pronounced in the 450 mm/s
since the intensities of their PFs are higher compared to AB cases for which average grain size increased from 276.5
samples, which indicates that heat treatment causes more to 309 μm after heat treatment, while in the 750 mm/s
grains to align with similar orientation. Scanning speed cases, grain size increase was more moderate (from 242.1
affects the texture as well. The PF intensity of the 750 AB to 254.4 μm) after heat treatment. Grains of the 450 AB
is noticeably higher compared to that of 450 AB. The same condition are noticeably larger as compared to that of the
is true for heat-treated samples produced with different 750 AB condition for the reasons explained earlier, and
scanning speeds. similar relationship holds for the HT samples.
Figure 8 shows grain boundary misorientation As shown in Figure 9, the compositions of both AB
distributions for all four conditions. The distribution of and HT samples are overall uniform and close to the
all samples is not random and with exception of 450 HT, equiatomic composition of the original powder. There is
and all samples feature a single peak with an average a slight misbalance in Cr and Mn with the latter being in
misorientation around 45°. Grain boundaries with 45° a small depletion especially for the 450 mm/s samples.
misorientation mainly correspond to rotation around [100] This might be because during the SLM process, the surface
[55]
direction . Meanwhile, the small angle misorientation temperature of melt pools can exceed the boiling point of
(<15°) was reduced after heat treatment for both 450 and the alloy. The difference in vapor pressures on the melt
750 mm/s samples. The grain size was calculated using pool surface creates a driving force for vapor to leave the
one-dimensional parameter, which refers to the longest surface . Mn has the highest vapor pressure and lower
[58]
distance (diameter) between any two boundary points . melting temperature among other constituencies of the
[56]
A weighted averaging approach was used to calculate the HEA and thus can easily leave the melt pool . Such high
[59]
average grain size using the following equation : volatility of Mn agrees with the current results. Samples
[57]
1 n of 450 mm/s condition receive higher energy during SLM
d = n ∑ Ad , (I) process leading to higher melt pool temperatures, which
i
ii
∑ i= 0 A i k= 0 hold for longer time. Consequently, higher amount of
Mn has a chance to escape resulting in Mn depletion of
Where n is the number of grains, A is the area of 450 samples. Heat treatment obviously has no significant
i
grain I, and d is the diameter. As seen from Figure 8, heat effect on Mn content since 1000°C chosen for treatment
i

Figure 8. Grain boundaries misorientation distribution and grain area distribution for selective laser melting-produced CoCrFeMnNi using 450 and 750
mm/s scanning speeds before and after heat treatment.

Volume 2 Issue 1 (2023) 9 https://doi.org/10.36922/msam.42