Title: Characterization of an aluminum alloy hemispherical shell fabricated via direct metal laser melting

Abstract

The ability of additive manufacturing to directly fabricate complex shapes provides characterization challenges for part qualification. The orientation of the microstructures produced by these processes will change relative to the surface normal of a complex part. In this work, the microscopy and x-ray tomography of an AlSi10Mg alloy hemispherical shell fabricated using powder bed metal additive manufacturing are used to illustrate some of these challenges. The shell was manufactured using an EOS M280 system in combination with EOS-specified powder and process parameters. The layer-by-layer process of building the shell with the powder bed additive manufacturing approach results in a position-dependent microstructure that continuously changes its orientation relative to the shell surface normal. X-ray tomography was utilized to examine the position-dependent size and distribution of porosity and surface roughness in the 98.6% dense part. Optical and electron microscopy were used to identify global and local position-dependent structures, grain morphologies, chemistry, and precipitate sizes and distributions. The rapid solidification processes within the fusion zone (FZ) after the laser transit results in a small dendrite size. Cell spacings taken from the structure in the middle of the FZ were used with published relationships to estimate a cooling rate of ~9 × 10⁵ K/s.more » Uniformly-distributed, nanoscale Si precipitates were found within the primary α-Al grains. A thin, distinct boundary layer containing larger α-Al grains and extended regions of the nanocrystalline divorced eutectic material surrounds the FZ. Moreover, subtle differences in the composition between the latter layer and the interior of the FZ were noted with scanning transmission electron microscopy (STEM) spectral imaging.« less

Authors:

Holesinger, T. G.  ^[1];

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Carpenter, J. S. ^[1]; Lienert, T. J. ^[1]; Patterson, B. M. ^[1]; Papin, P. A. ^[1]; Swenson, H. ^[1]; Cordes, N. L. ^[1]

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+ Show Author Affiliations

1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

Publication Date:

Mon Jan 11 00:00:00 EST 2016

Research Org.:

Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1240726

Report Number(s):

LA-UR-15-29591
Journal ID: ISSN 1047-4838; PII: 1798

Grant/Contract Number:  

AC52-06NA25396

Resource Type:

Accepted Manuscript

Journal Name:

JOM. Journal of the Minerals, Metals & Materials Society

Additional Journal Information:

Journal Volume: 68; Journal Issue: 3; Journal ID: ISSN 1047-4838

Publisher:

Springer

Country of Publication:

United States

Language:

English

Subject:

42 ENGINEERING; 36 MATERIALS SCIENCE