Controlling Martensitic Transformation Characteristics in Defect-Free NiTi Shape Memory Alloys Fabricated Using Laser Powder Bed Fusion and a Process Optimization Framework

Laser powder bed fusion has been widely investigated for shape memory alloys, primarily NiTi alloys, with the goal of tailoring microstructures and producing complex geometries. However, processing high temperature shape memory alloys (HTSMAs) remains unknown. In our previous study, we showed that it is possible to manufacture NiTiHf HTSMA, as one of the most viable alloys in the aerospace industry, using SLM and investigated the effect of parameters on defect formation. The current study elucidates the effect of process parameters (PPs) on the functionality of this alloy. Shape memory properties and the microstructure of additively manufactured Ni-rich NiTiHf alloys were characterized across a wide range of PPs (laser power, scanning speed, and hatch spacing) and correlated with energy density. The optimum laser parameters for defect-free and functional samples were found to be in the range of approximately 60–100 J/mm3. Below an energy density of 60 J/mm3, porosity formation due to lack-of-fusion is the limiting factor. Samples fabricated with energy densities of 60–100 J/mm3 showed comparable thermomechanical behavior in comparison with the starting as-cast material, and samples fabricated with higher energy densities (>100 J/mm3) showed very high transformation temperatures but poor thermomechanical behavior. Poor properties for samples with higher energies were mainly attributed to the excessive Ni loss and resultant change in the chemical composition of the matrix, as well as the formation of cracks and porosities. Although energy density was found to be an important factor, the outcome of this study suggests that each of the PPs should be selected carefully. A maximum actuation strain of 1.67% at 400 MPa was obtained for the sample with power, scan speed, and hatch space of 100 W, 400 mm/s, and 140 µm, respectively, while 1.5% actuation strain was obtained for the starting as-cast ingot. These results can serve as a guideline for future studies on optimizing PPs for fabricating functional HTSMAs.

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On the printability and transformation behavior of nickel-titanium shape memory alloys fabricated using laser powder-bed fusion additive manufacturing

Journal of Manufacturing Processes ◽

10.1016/j.jmapro.2018.08.037 ◽

2018 ◽

Vol 35 ◽

pp. 672-680 ◽

Cited By ~ 16

Author(s):

M. Mahmoudi ◽

G. Tapia ◽

B. Franco ◽

J. Ma ◽

R. Arroyave ◽

...

Keyword(s):

Additive Manufacturing ◽

Shape Memory Alloys ◽

Shape Memory ◽

Nickel Titanium ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Transformation Behavior ◽

Powder Bed

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Machine-Learning Assisted Laser Powder Bed Fusion Process Optimization for AlSi10mg: New Microstructure Description Indices and Fracture Mechanisms

SSRN Electronic Journal ◽

10.2139/ssrn.3681162 ◽

2020 ◽

Author(s):

Qian Liu ◽

Hongkun Wu ◽

Moses J. Paul ◽

Peidong He ◽

Zhongxiao Peng ◽

...

Keyword(s):

Machine Learning ◽

Process Optimization ◽

Fusion Process ◽

Fracture Mechanisms ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Powder Bed

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A printability assessment framework for fabricating low variability nickel-niobium parts using laser powder bed fusion additive manufacturing

Rapid Prototyping Journal ◽

10.1108/rpj-01-2021-0024 ◽

2021 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Bing Zhang ◽

Raiyan Seede ◽

Austin Whitt ◽

David Shoukr ◽

Xueqin Huang ◽

...

Keyword(s):

Mechanical Properties ◽

Additive Manufacturing ◽

Uncertainty Quantification ◽

Process Optimization ◽

Powder Bed Fusion ◽

Assessment Framework ◽

Laser Powder Bed Fusion ◽

Content Type ◽

Powder Bed ◽

Analytical Thermal Model

Purpose There is recent emphasis on designing new materials and alloys specifically for metal additive manufacturing (AM) processes, in contrast to AM of existing alloys that were developed for other traditional manufacturing methods involving considerably different physics. Process optimization to determine processing recipes for newly developed materials is expensive and time-consuming. The purpose of the current work is to use a systematic printability assessment framework developed by the co-authors to determine windows of processing parameters to print defect-free parts from a binary nickel-niobium alloy (NiNb5) using laser powder bed fusion (LPBF) metal AM. Design/methodology/approach The printability assessment framework integrates analytical thermal modeling, uncertainty quantification and experimental characterization to determine processing windows for NiNb5 in an accelerated fashion. Test coupons and mechanical test samples were fabricated on a ProX 200 commercial LPBF system. A series of density, microstructure and mechanical property characterization was conducted to validate the proposed framework. Findings Near fully-dense parts with more than 99% density were successfully printed using the proposed framework. Furthermore, the mechanical properties of as-printed parts showed low variability, good tensile strength of up to 662 MPa and tensile ductility 51% higher than what has been reported in the literature. Originality/value Although many literature studies investigate process optimization for metal AM, there is a lack of a systematic printability assessment framework to determine manufacturing process parameters for newly designed AM materials in an accelerated fashion. Moreover, the majority of existing process optimization approaches involve either time- and cost-intensive experimental campaigns or require the use of proprietary computational materials codes. Through the use of a readily accessible analytical thermal model coupled with statistical calibration and uncertainty quantification techniques, the proposed framework achieves both efficiency and accessibility to the user. Furthermore, this study demonstrates that following this framework results in printed parts with low degrees of variability in their mechanical properties.

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