Columnar grain width control for SS316L via hatch spacing manipulation in laser powder bed fusion

This study provides a quantitative way to tailor the grain structure in laser powder bed fusion (LPBF). Square-bottomed columnar grains (SCGs) were developed with a certain width roughly equal to the hatch spacing. The development of SCGs relied on different distinguishable regions, which were identified based on the differences in microstructural features between the melt-pool side and centreline. High lattice rotation accumulated at the melt-pool centreline, leading to grain boundaries forming at the centreline regions. The ultrasonic attenuation measurements and microhardness tests further validated the controllable properties. The findings indicated a novel approach to customise the material property. IMPACT STATEMENT A method to quantitatively control the columnar grain width in laser powder bed fusion was uncovered. The controllable properties were indicated, and the formation mechanism was revealed.

Automated summary

This study presents a quantitative method for adjusting the grain structure in laser powder bed fusion. Square-bottomed columnar grains (SCGs) with a certain width were developed based on distinguishable microstructural features between the melt-pool side and centreline. The controllable properties of SCGs were validated through ultrasonic attenuation measurements and microhardness tests.