Nanotechnologies / Materials
Manufacturing and materials joining

Development of Ma-Wang model for solid-state bonding
mechanism of cold spray additive manufacturing
Joining and Welding Research InstituteProfessor Ninshu Ma

https://researchmap.jp/ma.ninshu

Specially Appointed Assistant Professor Qian Wang

https://researchmap.jp/Qian_WANG

Nanotechnologies / Materials

Abstract
Cold spray (CS) is a highly anticipated solid-state additive manufacturing (AM) technology. However, the lack of a suitable material
model for a long time has brought great obstacles to quantitative
CS modeling, limiting performance enhancement and technicalimprovement of CSAMed materials. In this research, a new material constitutive model (Ma-Wang model) was developed for CS
based on dislocation dynamics to quantitatively describe the strain
hardening, the normal strain rate hardening, the ultra-high strain
rate hardening, the thermal softening and the grain refining due todynamic recrystallization for elucidating the solid-state interfacial
bonding mechanisms Although Ma-Wang model was originally developed for CS, this material model has the potential to solve otherlarge deformation and ultra-high strain rate problems occurred inlaser peening and friction stir welding, etc.

▍ Background & Results
Additive manufacturing (AM) is widely used for the rapid anddirect fabrication of near-net components via layer-by-layer metaldeposition. Unlike in fusion-based AM technologies, in the cold
spray (CS) process, powders are deposited by kinetic energy
instead of thermal energy; hence, melting/solidification-related issues (e.g., oxidation, thermal stress, phase transformation, chemical degradation, and grain growth) can be minimized or eliminated.
Particularly, the chemical composition and microstructure of raw
materials remain almost unchanged, providing excellent flexibility
in designing the final deposits. However, the lack of a suitable material model for a long time has brought great obstacles to quantitative understanding of CS process phenomena. In this research,
the Ma-Wang model considering the roles of strain hardening, normal-range strain rate hardening, ultra-high strain rate hardening,
and thermal softening was developed for CS to break through thistechnical bottleneck (Fig. 1). The most classical CS materials, Cu,Al, Ni and their alloys were targeted to elucidate the mechanismsof extreme deformation due to CS and its role on dynamic recrystallization for interface bonding (Fig. 2). In addition, an enhanced
contour method combined with the XRD method was developed toachieve the three-dimensional measurement of CS residual stress,
and the arbitrary Lagrangian-Eulerian (ALE) method was used toavoid the mesh distortion to accurately reproduce the CS residualstress and reveal its formation mechanism (Fig. 3).

CS process study, the Ma-Wang model is expected to be applied
to clarify the large dynamic plasticity problems occurred in laser
peening, friction stir welding and other ultra-high speed impacting
processes in the future.

Fig. 1. Development of the Ma-Wang material model based on dislocation dynamics

Fig. 2. High-accuracy prediction of deformation, grain size, and solid-state bonding during CS▍ Significance of the research and Future perspective
This research provides theoretical guidance for effectively regulating the grain size, interfacial bonding, residual stress in CS
components and thereby improving the component quality andservice reliability. The Ma-Wang material model is the cornerstoneof future multi-scale CS simulations to quantify the process-microstructure-performance relationship. Besides the applications forFig. 3. Measured and predicted CS residual stress

P a t e n tWang, Qian; Ma, Ninshu; Luo, Xiao-Tao et al. Towards better understanding supersonic impact-bonding behavior of cold sprayed 6061-T6 aluminum alloy
based on a high-accuracy material model, Additive Manufacturing. 2021, 48 (102469), p.1-11. doi: 10.1016/j.addma.2021.102469
Wang, Qian; Ma, Ninshu; Takahashi, Makoto et al. Development of a material model for predicting extreme deformation and grain refinement during coldspraying, Acta Materialia. 2020, 199, p.326–339. doi: 10.1016/j.actamat.2020.08.052
UR
L http://www.jwri.osaka-u.ac.jp/research/research03_1.html
K e y w o r d additive manufacturing, cold spray, material model, stress-strain, strain rate, residual stress

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