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Title: Localized melt-scan strategy for site specific control of grain size and primary dendrite arm spacing in electron beam additive manufacturing

Abstract

In addition to design geometry, surface roughness, and solid-state phase transformation, solidification microstructure plays a crucial role in controlling the performance of additively manufactured components. Crystallographic texture, primary dendrite arm spacing (PDAS), and grain size are directly correlated to local solidification conditions. We have developed a new melt-scan strategy for inducing site specific, on-demand control of solidification microstructure. We were able to induce variations in grain size (30 μm–150 μm) and PDAS (4 μm - 10 μm) in Inconel 718 parts produced by the electron beam additive manufacturing system (Arcam®). A conventional raster melt-scan resulted in a grain size of about 600 μm. The observed variations in grain size with different melt-scan strategies are rationalized using a numerical thermal and solidification model which accounts for the transient curvature of the melt pool and associated thermal gradients and liquid-solid interface velocities. The refinement in grain size at high cooling rates (>104 K/s) is also attributed to the potential heterogeneous nucleation of grains ahead of the epitaxially growing solidification front. The variation in PDAS is rationalized using a coupled numerical-theoretical model as a function of local solidification conditions (thermal gradient and liquid-solid interface velocity) of the melt pool.

Authors:
ORCiD logo; ; ; ; ; ;
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1400202
DOE Contract Number:  
AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Acta Materialia; Journal Volume: 140; Journal Issue: C
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Raghavan, Narendran, Simunovic, Srdjan, Dehoff, Ryan, Plotkowski, Alex, Turner, John, Kirka, Michael, and Babu, Suresh. Localized melt-scan strategy for site specific control of grain size and primary dendrite arm spacing in electron beam additive manufacturing. United States: N. p., 2017. Web. doi:10.1016/j.actamat.2017.08.038.
Raghavan, Narendran, Simunovic, Srdjan, Dehoff, Ryan, Plotkowski, Alex, Turner, John, Kirka, Michael, & Babu, Suresh. Localized melt-scan strategy for site specific control of grain size and primary dendrite arm spacing in electron beam additive manufacturing. United States. doi:10.1016/j.actamat.2017.08.038.
Raghavan, Narendran, Simunovic, Srdjan, Dehoff, Ryan, Plotkowski, Alex, Turner, John, Kirka, Michael, and Babu, Suresh. Wed . "Localized melt-scan strategy for site specific control of grain size and primary dendrite arm spacing in electron beam additive manufacturing". United States. doi:10.1016/j.actamat.2017.08.038.
@article{osti_1400202,
title = {Localized melt-scan strategy for site specific control of grain size and primary dendrite arm spacing in electron beam additive manufacturing},
author = {Raghavan, Narendran and Simunovic, Srdjan and Dehoff, Ryan and Plotkowski, Alex and Turner, John and Kirka, Michael and Babu, Suresh},
abstractNote = {In addition to design geometry, surface roughness, and solid-state phase transformation, solidification microstructure plays a crucial role in controlling the performance of additively manufactured components. Crystallographic texture, primary dendrite arm spacing (PDAS), and grain size are directly correlated to local solidification conditions. We have developed a new melt-scan strategy for inducing site specific, on-demand control of solidification microstructure. We were able to induce variations in grain size (30 μm–150 μm) and PDAS (4 μm - 10 μm) in Inconel 718 parts produced by the electron beam additive manufacturing system (Arcam®). A conventional raster melt-scan resulted in a grain size of about 600 μm. The observed variations in grain size with different melt-scan strategies are rationalized using a numerical thermal and solidification model which accounts for the transient curvature of the melt pool and associated thermal gradients and liquid-solid interface velocities. The refinement in grain size at high cooling rates (>104 K/s) is also attributed to the potential heterogeneous nucleation of grains ahead of the epitaxially growing solidification front. The variation in PDAS is rationalized using a coupled numerical-theoretical model as a function of local solidification conditions (thermal gradient and liquid-solid interface velocity) of the melt pool.},
doi = {10.1016/j.actamat.2017.08.038},
journal = {Acta Materialia},
number = C,
volume = 140,
place = {United States},
year = {Wed Nov 01 00:00:00 EDT 2017},
month = {Wed Nov 01 00:00:00 EDT 2017}
}