Tailored grain morphology via a unique melting strategy in electron beam-powder bed fusion
Artikel i vetenskaplig tidskrift, 2021

This study presents a unique melting strategy in electron beam-powder bed fusion of Alloy 718 to tailor the grain morphology from the typical columnar to equiaxed morphology. For this transition, a specific combination of certain process parameters, including low scanning speeds (400–800 mm/s), wide line offsets (300–500 μm) and a high number of line order (#10) was selected to control local solidification conditions in each melt pool during the process. In addition, secondary melting of each layer with a 90° rotation with respect to primary melting induced more vigorous motions within the melt pools and extensive changes in thermal gradient direction, facilitating grain morphology tailoring. Four different types of microstructures were classified according to the produced grain morphology depending on the overlap zone between two adjacent melt pools, i.e., fully-columnar (overlap above 40 %), fully-equiaxed (overlap below 15 %), mixed columnar-equiaxed grains, and hemispherical melt pools containing mixed columnar-equiaxed grains (overlap ~20–25 %). The typical texture was <001>; however, the texture was reduced significantly through the transition from the columnar to equiaxed grain morphology. Along with all four different microstructures, shrinkage defects and cracks were also identified which amount of them reduced by a reduction in areal energy input. The hardness was increased through the transition, which was linked to the growth of the γʺ precipitates and high grain boundary density in the fully-equiaxed grain morphology.

Additive manufacturing

Electron beam-powder-bed fusion

Grain structure

Alloy 718

Melting strategy

Författare

P. Karimi

Högskolan Väst

E. Sadeghi

Högskolan Väst

Joakim Ålgårdh

GE Additive

Jonas Olsson

Högskolan Väst

Magnus Hörnqvist Colliander

Chalmers, Fysik, Mikrostrukturfysik

P. Harlin

Sandvik Additive Manufacturing

Ehsan Toyserkani

University of Waterloo

Joel Håkan Andersson

Högskolan Väst

Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing

0921-5093 (ISSN)

Vol. 824 141820

Ämneskategorier

Keramteknik

Materialkemi

Metallurgi och metalliska material

Styrkeområden

Materialvetenskap

DOI

10.1016/j.msea.2021.141820

Mer information

Senast uppdaterat

2021-08-13