Enhancement of plastic deformation in ultrasound-assisted cold spray of tungsten: a molecular dynamics study

TL;DR

This study addresses the challenge of plastic deformation in tungsten during cold spray by leveraging ultrasound and acoustoplasticity, examined through atomistic molecular dynamics simulations. By applying ultrasonic perturbations to the substrate, the authors observe acoustic softening and transient interfacial heating that enhance plastic deformation, grain refinement, and interfacial bonding, across a range of velocities and particle sizes. The work extends to a V–W heterogeneous coating scenario, showing intermixing and altered mechanical responses that suggest a path to engineered alloys via ultrasound-assisted CSAM. The findings imply a practical route to process refractory metals and create uniform and heterogeneous coatings on-site without high-temperature treatment, though the study notes limitations in bridging to macroscale behavior and in modeling oxide layers and multi-particle tamping.

Abstract

Tungsten (W) is widely valued for its exceptional thermal stability, mechanical strength, and corrosion resistance, making it an ideal candidate for high-performance military and aerospace applications. However, its high melting point and limited room-temperature plasticity pose significant challenges for processing W using additive manufacturing (AM). Cold spray (CS), a solid-state AM process that relies on high-velocity particle impact and plastic deformation, offers a promising route for additive manufacturing of W, yet conventional CS fails to induce sufficient plastic deformation for effective bonding. In this study, we employ atomistic simulations to investigate the effect of ultrasonic perturbation in enhancing plastic deformation during CS of W, with a focus on acoustoplasticity-driven deformation mechanism. We show that ultrasonic perturbation leads to pronounced acoustic softening and promotes transient temperature elevation at the particle-substrate and particle-particle interfaces, thereby enhancing plastic deformation compared to non-ultrasound-assisted CS. Additionally, our results show that the coupled effects of acoustic softening and enhanced transient thermal activation lead to substantial improvements in interfacial bonding across a wide range of impact velocities, particle sizes, and ultrasonic parameters. Finally, we analyze the feasibility of ultrasound-assisted CS for manufacturing heterogeneous interfaces consisting of an equimolar Vanadium (V)-Tungsten (W) coating on a W substrate. Simulations reveal distinct mechanical behavior and dislocation densities compared to the homogeneous W on W CS configurations. Overall, this work highlights the potential of ultrasound-assisted cold spray as an effective strategy for manufacturing uniform coatings and engineered alloys, thereby addressing critical limitations in the additive manufacturing of refractory metals.

Figures (21)

• Figure 1: Schematic diagram of the cold spray simulation
• Figure 2: Variation of atomic configurations of $W$ particles and substrate after $t=0.5$ ns following an impact at a velocity, $v=800$ ms$^{-1}$\ref{['fig:800_no_ultra_cal']} without ultrasonic perturbation and, \ref{['fig:800_ultra_cal']} subjected to an ultrasonic perturbation with the amplitude of $A=3.165\textup{\AA}$ and frequency, $f=10$ GHz. The number of different lattice structures and dislocations corresponding to each atomic configuration is shown below the figures. The complete dynamic evolution of CS particles following impact can be observed in the supplementary videos.
• Figure 3: Variation of \ref{['fig:energy_track']} substrate potential energy and \ref{['fig:temp_track']} temperature of bottom particle as a function of time at non-ultrasound and ultrasound-assisted cases.
• Figure 4: Variation of mean square displacement of the bottom $W$ particle as a function of time in the presence and absence of ultrasonic perturbation with the amplitude of $A=3.165\textup{\AA}$ and frequency, $f=10$ GHz at an impact velocity of $v=800$ ms$^{-1}$ .
• Figure 5: Variation of mean von Mises strain of the bottom $W$ particle as a function of time in the presence and absence of ultrasonic perturbation with the amplitude of $A=3.165\textup{\AA}$ and frequency, $f=10$ GHz.