Mechanical and Penetration Properties of Additively Manufactured Tungsten Alloys
Release time:
2026-10-27
Tungsten alloys possess high density, high strength, high hardness, good high-temperature resistance, and excellent penetration capabilities, and are widely used in applications such as armor-piercing projectile cores, prefabricated fragments for high-explosive warheads, and thermal protection components for spacecraft [1–3]. Compared to traditional materials such as steel and aluminum alloys, tungsten alloys used for penetration have a higher density, enabling greater mass concentration, which helps improve the penetrator’s momentum, penetration capability, and terminal lethality [4]. Furthermore, their high strength and hardness meet the structural load-bearing and deformation resistance requirements of armor-piercing projectiles during launch and high-speed flight [5]. Therefore, tungsten alloys are considered important engineering materials for high-performance, high-lethality munitions.
Although tungsten alloys possess significant application value in the defense sector due to their excellent comprehensive properties, their processing and manufacturing still face numerous engineering challenges [6]. Tungsten has a high ductile-to-brittle transition temperature (approximately 200–400 °C) and a low recrystallization temperature (1,200 °C); and exhibits pronounced brittleness at room temperature, which limits its plastic deformation and formability [7]. This results in issues such as high processing temperatures, difficult forming, severe tool wear, and low material utilization during traditional casting, forging, and machining processes. Particularly for complex three-dimensional components, traditional manufacturing processes typically require multiple steps; furthermore, defects such as cracks, porosity, residual stresses, and microstructural inhomogeneities may arise during processing, thereby limiting the engineering applications of complex tungsten alloy components [8–9].
The development of additive manufacturing technologies has provided a new technical approach to addressing the challenges of forming and processing complex tungsten alloy components. Among these, Powder Extrusion Printing (PEP) is an indirect additive manufacturing process. It uses an oil-wax composite binder to prepare a slurry of ultrafine tungsten powder with a high solid phase content. Through extrusion, near-net-shape green parts with complex structures are formed, which are then densified into tungsten alloy components via subsequent debinding and sintering [10]. Compared to direct energy-input additive manufacturing methods such as laser and electron beam processes, PEP employs low-temperature extrusion molding technology, which avoids metallurgical damage and thermal stress issues caused by extreme localized thermal loads and severe thermal gradients during the printing process. This process enables the fabrication of porous, hollow, and integrated complex tungsten components without the need for molds. The accompanying two-step solvent-thermal degreasing process completely removes organic components, eliminates carbon impurity contamination, and reduces the requirements for the morphology and flowability of the raw powder; compared to traditional tungsten alloy fabrication processes, it reduces defects caused by uneven shrinkage and thermal tearing [11–13]. Therefore, PEP offers advantages such as low mold dependency, high material utilization, minimal machining allowance, strong capability for forming complex structures, and a short production cycle, providing a new technical solution for the efficient manufacturing of complex tungsten alloy components.
Currently, research on the preparation of tungsten alloys via the PEP process has primarily focused on optimizing the forming process and controlling densification; however, systematic experimental studies on static and dynamic mechanical properties, deformation response patterns at high strain rates, and penetration damage characteristics are still lacking. The mechanisms underlying dynamic deformation and penetration effects remain unclear, which limits the engineering application of such tungsten alloys in defense equipment fields such as armor-piercing projectile cores and preformed fragments. Therefore, conducting systematic research on the mechanical properties and penetration capabilities of powder-extruded 3D-printed tungsten alloys to clarify their mechanical behavior patterns and underlying mechanisms holds significant practical importance for advancing the engineering applications of this process.
To investigate the mechanical properties and penetration capabilities of powder-extruded 3D-printed tungsten alloys, this study conducted quasi-static compression tests to determine the material’s quasi-static deformation and compressive strength; a split Hopkinson probe was used to perform high-strain-rate dynamic impact tests to investigate the material’s mechanical response under high strain rates; a light gas cannon test platform was utilized to conduct penetration tests of tungsten alloy rod projectiles and fragments against metal target plates, and numerical simulation methods were employed to model the penetration process; and by combining microstructural characterization before and after the tungsten alloy tests, the dynamic deformation mechanism of the material was elucidated.
1 Materials and Methods
1.1 Material Preparation
The preparation process for 93W tungsten alloy material for powder extrusion printing is shown in Figure 1. The specific process is as follows: 93W tungsten powder (nickel-to-iron mass ratio of 7:3) and a wax-based polymer binder were thoroughly mixed in a banbury mixer to ensure the binder uniformly coated the powder particles; Subsequently, the mixture was processed through a granulator via a filament drawing process to obtain 93W composite particles with uniform particle size, ensuring stable material feeding during the subsequent printing process. A 3D model of the cylindrical rod required for the experiment was created using 3ds Max software, and the appropriate printing parameters for the tungsten alloy were determined; a 3D printer capable of powder extrusion was used to fabricate the tungsten alloy cylindrical rod green body, ensuring the green body had an intact external shape and a continuous internal structure. The formed green bodies were subjected to a two-step solvent degreasing and thermal degreasing process to remove the binder: First, the green bodies were placed in a water bath and heated to 50 °C, where n-heptane was used to leach out some of the polymer components, thereby initially reducing the binder content within the green bodies; the green body is then immersed in kerosene to displace residual solvent from the pores, followed by thorough drying in a drying oven to remove the solvent. The green body is subsequently transferred to a thermal degreasing unit, where thermal degreasing is completed at a maximum temperature of 600 °C to achieve complete removal of the polymer binder. To prevent sintering defects, the degreased tungsten alloy green body is placed in a sintering furnace and pre-sintered at 1,000 °C. This process promotes the formation of sintering necks in the powder particles and establishes initial bonding, thereby enhancing the green body’s strength and preventing cracking during subsequent machining processes; High-temperature sintering is then performed at the target sintering temperature, where pore elimination is achieved through particle rearrangement and solid-state diffusion, ultimately yielding high-density 93W tungsten alloy rods.
1.2 Testing Methods
Microstructural characterization was performed using a SU-5000 scanning electron microscope to observe the specimen morphology, and an integrated energy dispersive X-ray spectrometer (EDS) was used to analyze the composition and distribution of alloying elements; quasi-static mechanical property testing was conducted using an MTS 810 universal testing machine. Specimen dimensions were Φ6 mm × 9 mm, with a compressive loading strain rate set at 10–3 s–1. Each test series was repeated three times to ensure data stability; High-strain-rate dynamic mechanical property testing was conducted using a 16 mm diameter split Hopkinson pressure bar (SHPB) apparatus independently developed by the laboratory, with test specimens measuring Φ5 mm × 5 mm; penetration tests were performed using a first- and second-stage hybrid light-gas cannon test system independently developed by the laboratory. The test projectiles included two specifications: cylindrical fragments measuring Φ8 mm × 8 mm and long-rod projectiles measuring Φ9 mm × 90 mm. The experimental system is shown in Figure 2.
1.3 Numerical Simulation Methods
Autodyn software was used to conduct dynamic numerical simulations of high-speed penetration of target plates by tungsten alloy penetrators; the mechanical behavior of the materials was described using the Johnson-Cook (JC) constitutive model. The JC model effectively characterizes the work hardening, damage, and fracture failure characteristics of materials under high strain rates, large plastic deformation, and impact loads, making it suitable for high-speed penetration simulation scenarios. In the simulation, both the rod projectile and the fragment were modeled using Lagrangian meshes. This type of mesh moves synchronously with the material particles, ensuring high computational accuracy and effectively avoiding the issues of mesh distortion and computational inaccuracies commonly found in conventional impact simulations. The rod-spring is a cylindrical structure with geometric dimensions set at 90 mm in length and 9 mm in diameter; the fragment has a diameter of 8 mm and a length of 8 mm; the target plate is made of 603 armor steel, measuring 100 mm in length, 100 mm in width, and 30 mm in thickness. The three-dimensional simulation model is shown in Figure 3. The material constitutive parameters required for the simulation calculations are as follows: for quasi-static analysis, initial yield strength A = 700 MPa; strain hardening coefficient B = 2,018 MPa; strain hardening index n = 0.425; and strain rate sensitivity coefficient C = 0.8813. All of the above parameters were obtained by fitting data from quasi-static and high-strain-rate dynamic mechanical tests.
2 Microstructural Analysis
2.1 Characterization of the 3D-Printed 93W Tungsten Alloy
The microstructure and elemental distribution of the as-printed 3D-printed 93W tungsten alloy are shown in Figure 4. As shown in the figure, the alloy exhibits a typical two-phase microstructure: light-gray, nearly equiaxed tungsten grains are uniformly distributed and interlock to form the alloy’s hard matrix; the interstitial spaces between the tungsten grains consist of a dark, continuous, network-like binder phase. The interfaces between the two phases are well-bonded, with no obvious interfacial cracking; only a small number of microscopic sintering pores are present in localized areas. EDS results on elemental distribution indicate that W is completely enriched within the grains, with a uniform distribution and no obvious segregation; Ni and Fe, on the other hand, are entirely segregated at the boundaries and interstitial regions of the tungsten grains. Their spatial distributions overlap significantly, jointly constituting the alloy’s binder phase. No abnormal precipitation or agglomeration of elements was observed.
2.2 Mechanical Property Testing
Figure 5 shows the stress–strain curves of the 93W tungsten alloy under quasi-static and dynamic compression conditions at different strain rates; the mechanical property parameters are listed in Table 1. Under quasi-static loading (strain rate of 10–3 s–1), the alloy’s yield strength was 671 MPa, and the stress continued to rise as deformation progressed, exhibiting continuous work hardening characteristics. In the high strain rate loading range of 1,725–4,511 s^(−1), the alloy’s yield strength exhibited a monotonically increasing trend with rising strain rate, gradually rising from 1,514 MPa to 1,855 MPa, demonstrating a significant positive strain rate hardening effect. This indicates that under high-strain-rate impact, the material’s resistance to plastic deformation continuously increases as the loading rate rises.
2.3 Penetration Capability
To systematically evaluate the penetration performance of 3D-printed 93W tungsten alloy under various munition operating conditions, and to elucidate the influence of the projectile’s aspect ratio on penetration modes and energy release patterns, two types of test specimens were prepared: cylindrical fragments with a small aspect ratio and rod-shaped projectiles with a large aspect ratio. These correspond to two typical engineering applications: prefabricated fragments in high-explosive warheads and the cores of armor-piercing projectiles. Penetration tests were conducted using the two projectiles made of 93W tungsten alloy against half-infinite-thickness target plates; the rod-shaped projectile measured Φ9 mm × 90 mm, while the cylindrical fragment measured Φ8 mm × 8 mm. The macroscopic morphology of the craters formed by the two projectiles after penetration is shown in Figure 6, and the corresponding statistical data on penetration performance parameters are presented in Table 2, where penetration efficiency is defined as the ratio of penetration depth to the original length of the projectile.
The results show that for the cylindrical fragment, within the impact velocity range of 753–1,217 m/s, the penetration depth increased from 8.1 mm to 10.2 mm—an increase of approximately 26%. This demonstrates that the penetration behavior of short cylindrical fragments is dominated by radial extrusion deformation, and that an increase in velocity has a more significant effect on enhancing their axial penetration capability; In contrast, the long rod projectile produced a crater diameter of only 9.1 mm at a penetration velocity of 1,476 m/s—significantly smaller than the radial damage range of the cylindrical fragment—while achieving a penetration depth of 77.5 mm. This indicates that the projectile’s high length-to-diameter ratio concentrates the impact energy highly in the axial direction, resulting in a deep penetration mechanism that is fundamentally different from that of the short cylindrical fragment.
In terms of penetration efficiency, for cylindrical fragments within the impact velocity range of 753–1,217 m/s, penetration efficiency exhibited a monotonically increasing trend with rising velocity, rising from 101.3% to 127.5%, with penetration efficiency exceeding 100% under all operating conditions. For long-rod projectiles, the penetration efficiency of the 3D-printed 93W tungsten alloy long-rod projectile at an impact velocity of 1,476 m/s was 86.1%; Compared to a conventional sintered 93W tungsten alloy long-rod projectile at the same velocity (penetration efficiency of 85.1%), the energy utilization efficiency of the two was essentially at the same level, with the 3D-printed specimen showing a slight improvement in penetration efficiency. The results indicate that while the powder extrusion printing process enables near-net-shape manufacturing of complex structures and overcomes the limitations of traditional manufacturing processes, the penetration performance of the resulting tungsten alloy material can reach the same level as that of traditional liquid-phase sintered alloys, providing a solid foundation for engineering applications.
Scanning electron microscopy (SEM) characterization was performed on the projectile head of the long-rod projectile recovered after penetration; the results are shown in Figure 7. Observation along the penetration axis reveals that the tungsten particles in the projectile head region exhibit distinct signs of extrusion deformation, with the particles undergoing oriented plastic flow and morphological reorganization along the direction of force application. Further comparison of the deformation orientation revealed that the direction of extrusion deformation of the tungsten particles aligns with the penetration axis, and the surface layer of the projectile head exhibits significant localized shear flow characteristics. This microstructural deformation behavior can, to a certain extent, delay the overall upsetting and blunting of the projectile, reduce kinetic energy dissipation caused by radial hole expansion and lateral material accumulation, and concentrate more energy on the axial penetration process.
3 Simulation
To verify the computational accuracy and reliability of the numerical model, the simulation results were validated against experimentally measured penetration morphologies and characteristic parameters, as shown in Figure 8. From the overall cross-sectional morphology, it can be seen that under both the long-rod projectile and cylindrical fragment penetration conditions, the simulated crater contours and projectile deformation patterns agree well with the experimental results. Under the long-rod projectile condition, the simulation reproduced the “narrow and deep” axial penetration morphology; the deformation pattern at the projectile’s nose was consistent with the macroscopic deformation behavior of the recovered projectile from the test. Under the cylindrical fragment condition, the simulation accurately reproduced the “wide and shallow” bowl-shaped crater morphology dominated by radial fragment extrusion; the lateral material accumulation at the target plate opening also matched the experimental observations.
A further quantitative comparison of key performance parameters revealed that the relative errors between the simulated and experimentally measured values for penetration depth and crater diameter under both conditions were less than 5%, meeting the accuracy requirements for engineering calculations. The above results indicate that the Johnson-Cook constitutive model selected in this study, along with the material parameters derived from mechanical testing, can accurately characterize the dynamic mechanical response of 3D-printed 93W tungsten alloy under high-speed impact loads. The established penetration simulation model demonstrates good reliability and can support in-depth analysis of the flow behavior and deformation mechanisms of projectile and target materials in subsequent studies.
Figure 9 shows the results of a numerical simulation of the penetration process of a 93W tungsten alloy long-rod projectile into a half-infinite-thickness target plate using additive manufacturing. Based on the mechanical characteristics of the projectile-target interaction and the evolution of the morphology, the entire penetration process can be divided into the pit-formation stage, the stable penetration stage, and the penetration termination stage. Figure 9(a) illustrates the initial crater formation stage, during which the long-rod projectile strikes the target surface at high speed, instantly generating an impact pressure in the contact region that far exceeds the target material’s yield strength; under the action of strong dynamic loads, the surface layer of the target undergoes violent plastic flow, extruding radially and toward the free surface to form a crater rim. At the same time, the projectile’s nose begins to undergo plastic deformation due to the impact reaction force. During this stage, the penetration depth is shallow, and the crater morphology has not yet reached a stable state; the pressure contour map at this point is shown in Figure 9(b). Figure 9(c) depicts the steady-state penetration phase, which is the core stage during which the penetration depth increases. As penetration continues, the projectile-target interaction gradually reaches a dynamic equilibrium; the axial penetration resistance remains essentially constant, and the penetration depth increases approximately linearly with time; During this stage, the diameter of the crater sidewalls remains relatively stable, and the target material flows continuously and uniformly backward along the side of the projectile. Under the coupled action of impact normal stress and shear stress, the projectile nose maintains a self-sharpening morphology, ensuring sustained and efficient axial penetration capability. Figure 9(d) illustrates the penetration termination stage. When the projectile’s remaining kinetic energy is insufficient to overcome the penetration resistance of the target plate, the penetration velocity continues to decay until it reaches zero, marking the end of the penetration process. The residual projectile undergoes swaging deformation and comes to rest at the bottom of the crater, ultimately forming an elongated crater with a slightly wider entrance and a narrower interior. This fully demonstrates the performance characteristics of the long-rod projectile, namely its concentrated energy and outstanding deep penetration capability. The simulation results for the penetration termination stage are shown in Figure 9(e).
Figure 10 shows the simulation of the entire process—from impact to plastic deformation and sustained penetration—of an additively manufactured tungsten alloy cylindrical fragment within the 0–29 μs time interval. During the initial impact phase, the projectile head undergoes plastic flow under compression; as penetration continues, the material at the edges on both sides of the projectile gradually undergoes shear curling and detaches, effectively suppressing overall projectile swelling and blunting. In contrast, in traditional tungsten alloys, the internal tungsten grains are interconnected, resulting in high continuity of the tungsten phase. Under high-speed impact, the material tends toward uniform plastic deformation, making it difficult to induce localized adiabatic shear failure; the projectile is highly prone to flattening and cannot form an effective “self-sharpening” effect.
The pressure distribution contour plots for the cylindrical fragment at the initial impact stage (5 μs) and the stable penetration stage (20 μs) are shown in Figure 11, illustrating the evolution of impact pressure in the projectile-target system during penetration. At 5 μs, the projectile has just made contact with the target plate; the peak pressure at the interface reaches 1.784 × 10⁷ kPa. The high-pressure zone is concentrated along the edges on both sides of the projectile-target contact interface, while the central region of the projectile exhibits negative pressure; Localized high pressure at the edges causes the material on the outer periphery of the projectile to undergo plastic instability first, generating adiabatic shear that drives the material on both sides of the projectile to roll and deform, gradually forming a relatively sharp projectile contour. When penetration reaches 20 μs, the high-pressure zone shifts to the leading edge of the penetration crater in the target plate, forming a continuous arc-shaped high-pressure band. The peak pressure drops to 2.240 × 10⁶ kPa, and the pressure diffuses layer by layer axially into the depths of the target; The sharp projectile contour formed at this stage concentrates the impact pressure more effectively in the direction of penetration, thereby suppressing lateral pressure diffusion toward the target plate to a certain extent. In contrast, the pressure distribution of the projectile formed from conventional liquid-phase sintered tungsten alloys after impact is more uniform; during deformation, these alloys are more prone to overall upsetting and blunting, causing more of the impact energy to be dissipated during the lateral expansion of the target hole. Overall, the powder-extruded 93W tungsten alloy exhibits high initial edge pressure that induces edge shear deformation during penetration, followed by a contour that continuously focuses the axial load after deformation. This coupling mechanism between deformation and load transfer allows more kinetic energy to be directed toward axial penetration of the target plate, thereby helping to improve the utilization efficiency of penetration energy.
Figure 12 shows the residual velocity-time curves of a long-rod projectile and a cylindrical fragment during penetration of the target plate. The figure also presents the projectile-target interaction morphology corresponding to typical penetration moments, revealing significant differences in the dynamic evolution characteristics between the two. Figure 12(a) corresponds to the penetration process of the long-rod projectile, with an initial impact velocity of approximately 1,476 m/s; the entire penetration process lasts about 90 μs. Based on the velocity decay pattern, this process can be divided into two stages. The early penetration phase (0–60 μs) is a stable penetration stage, during which the projectile velocity decreases slowly in an approximately linear manner over time, decaying from an initial 1,476 m/s to approximately 1,200 m/s; During this stage, the projectile-target interaction reaches dynamic equilibrium; the penetration resistance remains essentially constant; the projectile’s nose maintains a self-sharpening profile; and it continues to advance into the target plate, with the penetration depth increasing steadily. The late penetration phase (60–90 μs) is the termination stage. As the projectile’s mass is continuously eroded and depleted, the remaining kinetic energy becomes insufficient to sustain stable penetration. The rate of velocity decay accelerates significantly until, at approximately 90 μs, the projectile’s velocity drops to 0, ending the penetration process and ultimately forming a slender crater with a high depth-to-diameter ratio.
Figure 12(b) illustrates the penetration process of a cylindrical fragment. The projectile’s initial velocity is approximately 1,217 m/s, and the entire penetration process lasts only about 22 μs, with a velocity decay rate far higher than that of the long-rod projectile. After the fragment strikes the target plate, its velocity decreases rapidly and monotonically, without a distinct stable penetration plateau. This is because the cylindrical fragment has a small length-to-diameter ratio and limited total kinetic energy; following impact, deformation is primarily driven by plugging and radial compression. As the target plate’s resistance increases rapidly with penetration depth, the projectile’s kinetic energy is rapidly dissipated within a short time, ultimately forming a shallow, wide, bowl-shaped crater.
A comparison of the velocity evolution characteristics of the two types reveals that the projectile’s length-to-diameter ratio is the key factor determining penetration dynamics: long-rod projectiles, with their high length-to-diameter ratio and high axial energy density, can maintain a stable penetration state for a longer duration, exhibiting a gradual velocity decay and ultimately achieving deep penetration; in contrast, short cylindrical fragments concentrate their energy on the target’s surface layer, with a high proportion of radial energy dissipation, resulting in rapid velocity decay and limited penetration depth.
4 Conclusions
This paper investigates a 93W-Ni-Fe tungsten alloy fabricated via powder extrusion printing. Through a combined approach involving microstructural characterization, static and dynamic compression tests, light gas gun penetration tests, and numerical simulation, the microstructural characteristics, dynamic mechanical response patterns, and penetration failure mechanisms of this alloy were systematically studied, leading to the following main conclusions:
(1) The 93W tungsten alloy prepared by powder extrusion printing exhibits a typical two-phase microstructure: nearly equiaxed tungsten grains are uniformly distributed and form a hard matrix, while the Ni-Fe binder phase is distributed in a continuous network along the interstices between the tungsten grains; Element distribution is uniform with no significant segregation; the mass fractions of W, Ni, and Fe are essentially consistent with the nominal composition of the 93W tungsten alloy. The interfaces between the two phases are well bonded, with only a small number of microscopic pores present locally, resulting in excellent overall quality.
(2) The 93W tungsten alloy exhibits significant strain rate sensitivity. Under quasi-static loading, the alloy displays continuous work hardening characteristics, with a yield strength of 671 MPa; In the high strain rate range of 1,725–4,511 s–1, the alloy’s yield strength gradually increased from 1,514 MPa to 1,855 MPa as the strain rate rose, demonstrating a pronounced positive strain rate hardening effect.
(3) There are differences in the penetration performance between the two types of structural projectiles. Cylindrical fragments undergo primarily radial extrusion deformation; within the velocity range of 753–1,217 m/s, the crater diameter increases slowly with penetration velocity, while the increase in penetration depth is more significant; long-rod projectiles, on the other hand, exhibit small-diameter, deep-penetration characteristics, with a penetration depth reaching 77.5 mm at a penetration velocity of 1,476 m/s. Microstructural analysis indicates that the oriented plastic flow and progressive flaking of tungsten particles along the shear direction constitute the core microstructural mechanism underlying their excellent deep penetration capability.
(4) Numerical simulation results show that the penetration process of the long-rod projectile can be divided into three stages: the cratering stage, the stable penetration stage, and the penetration termination stage; During the stable penetration phase, the projectile-target interaction reaches dynamic equilibrium; penetration resistance remains essentially constant, projectile velocity decays gradually, and penetration depth increases linearly; cylindrical fragments do not exhibit a distinct stable penetration phase, and their velocity decay rate is significantly higher than that of the long-rod projectile, with kinetic energy rapidly dissipating into the radial deformation of the target plate.
References: Mechanical and Penetration Properties of Additively Manufactured Tungsten Alloys—Chen Wenjie, Huang Jiahao, He Chenbin, Gao Yuan, Zheng Yuxuan, Cheng Chun*
(Key Laboratory of Impact and Safety Engineering, Ministry of Education, Ningbo University, Ningbo, Zhejiang 315211) DOI: 10.20098/j.cnki.1001-5132. 2026.0816;
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