A1 Journal article (refereed), original research

Laser powder bed fusion of Ni-Mn-Ga magnetic shape memory alloy


Open Access hybrid publication

Publication Details
Authors: Laitinen Ville, Sozinov Oleksii, Saren Andrey, Salminen Antti, Ullakko Kari
Publisher: Elsevier
Publication year: 2019
Language: English
Related Journal or Series Information: Additive Manufacturing
ISSN: 2214-7810
eISSN: 2214-7810
JUFO-Level of this publication: 2
Open Access: Open Access hybrid publication

Abstract

Additive manufacturing (AM) has gone through major developments in the
past decade, enabling the rapid manufacture of complex geometries from
traditional engineering materials. This study aims to facilitate the
development and additive manufacturing of a new generation of fast and
simple digital components with integrated magnetic shape memory (MSM)
alloy sections that can be actuated by an external magnetic field. Here,
we employ a systematic design of experiments (DoE) approach for
investigating laser powder bed fusion (L-PBF) of a Ni-Mn-Ga based MSM
alloy. The effects of the applied process parameters on the chemical
composition and relative density are determined, and detailed
investigations are conducted on the microstructural properties of the
as-deposited material obtained using optimized parameters. The results
show that although the L-PBF of Ni-Mn-Ga is characterized by an
ever-present loss of Mn, deposition of Ni-Mn-Ga with a high relative
density of 98.3% and a minimal loss of Mn at ∼1.1 at.% is feasible. The
material produced in this manner was compositionally near homogenous
and, in as-deposited condition, consisted of a mixture of 14 M and
non-modulated (NM) martensites. However, combined measurements by the
low-field ac magnetic susceptibility method (LFMS) and DSC revealed that
the phase transformation of the as-deposited material from martensite
to austenite, and vice versa, was broad and occurred in a paramagnetic
state. Inspection by SEM revealed a layered microstructure with a
stripe-like surface relief that originated from the presence of
martensitic twins within the sample. Additionally, AFM and MFM
measurements showed that in as-deposited Ni-Mn-Ga, there exists a weak
MFM contrast that can be attributed to the twinned martensite having
magnetic anisotropy. Overall, L-PBF shows high potential for the
production of functional Ni-Mn-Ga based MSM alloys.


Last updated on 2020-20-03 at 10:03