Rapid Solidification Process Research Articles

Enhancing strength-ductility synergy in nano-sized TiB2/Al composite via rapid solidification and thermo-mechanical processing

The Al-Cu-Mn (AA2219) composite reinforced by 5 wt% nano-sized TiB2 particles were fabricated by hot isostatic pressing (HIP) combined with thermal-mechanical processing to achieve a superior strength-ductility combination. Coupling the comprehensive characterizations and microstructure-based analysis, the strength-ductility mechanisms were deeply understood. Results reveal that the uniform dispersed nano-sized TiB2 particles under the current preparation process helps to improve the mechanical properties of the composite. The introduction of pre-stretch before artificial aging produced a fine θ' and S precipitates. By combining high-resolution TEM and crystal structure analysis, Al(Cu) and S phase at TiB2/Al interface were identified, and their mismatch (δ) with Al were 3.8 % and 4.8 %, respectively. Mechanisms related to pre-stretch effects on the formation of dislocation, θ' and S precipitates and corresponding structures are discussed, as well as the implications of TiB2/Al interface characteristics on strength and ductility.

Probing rapid solidification pathways in refractory complex concentrated alloys via multimodal synchrotron X-ray imaging and melt pool-scale simulation

AbstractRefractory complex concentrated alloys (RCCAs) show potential as the next-generation structural materials due to their superior strength in extreme environments. However, RCCAs processed by metal additive manufacturing (AM) typically suffer from process-related challenges surrounding laser material interaction defects and microstructure control. Multimodal in situ techniques (synchrotron X-ray imaging and diffraction and infrared imaging) and melt pool-level simulations were employed to understand rapid solidification pathways in two representative RCCAs: (i) multi-phase BCC + HCP Ti0.4Zr0.4Nb0.1Ta0.1 and (ii) single-phase BCC Ti0.486V0.375Cr0.111Ta0.028. As expected, laser material interaction defects followed similar systematic trends in process parameter space for both alloys. Additionally, both alloys formed a single-phase (BCC) microstructure after rapid solidification processing. However, significant differences in microstructure selection between these alloys were discovered, where Ti0.4Zr0.4Nb0.1Ta0.1 showed a mixture of equiaxed and columnar grains, while Ti0.486V0.375Cr0.111Ta0.028 was dominated by columnar growth. These behaviors were well described by the influence of undercooling effects on columnar-to-equiaxed transition (CET). Distinct microstructure formation in each alloy was verified through CET predictions via analytical melt pool simulations, which showed a ~ 5 × increase degrees in undercooling for Ti0.4Zr0.4Nb0.1Ta0.1 compared to Ti0.486V0.375Cr0.111Ta0.028. Overall, these results show that microstructure control based on modulating the freezing range must be balanced with process considerations which resist defect formation, such as solidification crack formation in RCCAs. Graphical abstract

Impact of Iron Contamination on Liquid Properties and Microstructural Evolution in AlSi20

Additive manufacturing processes enable highly flexible and scalable shaping while maintaining rapid solidification processing conditions. This combination makes additive manufacturing particularly attractive for recycling contaminated alloys, as it allows critical brittle phases to be refined and utilized as alloying elements. However, little is known about the impact of contaminants on the fluid properties of liquid metals. Herein, thermodynamic modeling and experimental methods are combined to investigate the properties of AlSi20 and its contaminated variant, (AlSi20)95Fe5. The oscillating droplet method is used to experimentally determine surface tension and analyze solidified droplets to evaluate microstructure for different cooling rates. The findings indicate that while contaminants have a minor effect on fluid properties, they significantly influence microstructural properties.

Additive manufacturing of sustainable and heat-resistant Al-Fe-Mo-Si-Zr alloys

Improving the sustainability of metals and alloys is essential for slowing down global warming. The reason is that their extraction and production stand for about 40% of all greenhouse gas emissions in the industrial sector. This motivates new alloy design and processing criteria such as the (1) preferred use of abundant and sustainable alloying elements and (2) improved material tolerance against impurity intrusion from recycling. In this context, additive manufacturing (AM) is attractive, through rapid solidification, capable of quenching impurities into a solid solution state, avoiding formation of large intermetallics and introduction of metastable phases. Here, by using this approach we show how iron, an important scrap-related contaminant in aluminum alloys, can be turned from a harmful into a valuable ingredient. Specifically, the addition of Mo and Si facilitates the formation of beneficial metastable body-centred cubic (BCC) Al12(Fe, Mo)3Si phase, instead of more stable but detrimental intermetallic variants commonly observed in Al-Fe alloys. The as-built microstructures have excellent thermal stability, tested up to 200hours at 300 °C, because of low diffusivity of Fe and the formation of Zr shell. We find that for such supersaturated alloys, two issues are important, namely (a) the heterogeneous microstructures in the as-built condition, (b) the evolution of metastable precipitates during heating. We suggest that this type of approach help to guide sustainable alloy design via AM and other rapid solidification processes.

Mechanical Behavior of Additive Manufacturing (AM) and Wrought Ti6Al4V with a Martensitic Microstructure

Processing and microstructure are fundamental in shaping material behavior and failure characteristics. Additively manufactured materials, due to the rapid heating and solidification process, exhibit unique microstructures compared to their as-cast counterparts, resulting in distinct material properties. In this work, the response of the titanium alloy Ti6Al4V has been investigated for different processing conditions through quasi-static testing. AM Ti6Al4V was fabricated by employing Selective Laser Sintering (SLS) and Selective Laser Melting (SLM) techniques. Both materials present a similar microstructure consisting of an acicular martensitic α′-phase. Commercial Ti6Al4V-grade 5 (supplied as bars) was also examined after heat treatment to achieve a microstructure akin to the AM material. The heat treatment involved rapid heating above the β-phase region and water quenching to obtain a full martensite microstructure. A similar constitutive behavior and tensile–compressive asymmetry in strength were noted for the investigated materials. However, AM alloys exhibited a significantly higher deformation at failure, reaching nearly 40%, compared to only 6.1% for the wrought martensitic material, which can be attributed to the dissimilar distribution of both α′ laths and prior-β grain boundaries in the investigated materials. The results indicate that AM can be implemented for the fabrication of martensitic microstructures with mechanical properties superior to those obtained with conventional water-quenching.

Additive manufacturing nickel-aluminum bronze alloy via wire-fed electron beam directed energy deposition: Enhanced mechanical properties and corrosion resistance compared to as-cast counterpart

In the present work, a wall-structured nickel-aluminum bronze (NAB) alloy was fabricated via electron beam directed energy deposition (EB-DED) additive manufacturing with a single-pass multi-layer deposition strategy. A comprehensive comparative analysis of microstructure, mechanical properties, and corrosion resistance was conducted against a conventionally cast NAB alloy. The inherent rapid solidification and cyclic thermal processing of the EB-DED technique profoundly influenced the microstructural evolution of the NAB alloy. The as-deposited NAB alloy exhibited a fine-grained microstructure, devoid of the martensitic β′ phase, accompanied by the spheroidization of partial κIII precipitates, and a homogeneous distribution of alloying elements. These distinctive microstructural attributes synergistically enhanced the strength, hardness, and toughness of the NAB alloy, conferring superior mechanical properties compared to its cast counterpart. Furthermore, the as-deposited alloy demonstrated remarkable corrosion resistance in a 3.5 wt% NaCl solution, significantly outperforming the cast alloy. The underlying mechanisms governing the structure-property relationships were elucidated. This comprehensive investigation provided insights into the unique characteristics and potential applications of EB-DED fabricated NAB alloys, positioning them as promising candidates for high-performance components subjected to severe mechanical and corrosive service conditions.

Far-from-equilibrium solid–liquid interfacial properties of aluminum

Simulating quantitatively far-from-equilibrium conditions, which is relevant to a host of rapid solidification processes, has remained a major challenge where theoretical models and physical mechanisms for far-from-equilibrium solid–liquid (SL) interface are essential. Herein, we investigate the effects of far-from-equilibrium state and external strain on SL interfacial properties by using capillary fluctuation method and models based on transition rate theory. Under an extreme temperature gradient (TG), both SL interfacial stiffness (S) and SL interface velocity (v) are found to increase with TG. The nonlinear relationship between v and temperature is revealed over a large undercooling range (640 K). It is found that an external strain (ϵ) of 1%–3% could decrease S by 10%–30%. v is found to increase with external strains at large undercooling. Tensile strains decrease the activation energy (Q) and viscosity, thus facilitating SL interface movement. A strain-dependent Gibbs–Thomson condition is proposed by incorporating linear S-ϵ and Q-ϵ relations. Our systematically theoretical discussion on the far-from-equilibrium SL interfacial properties could provide a predictive guideline on SL interface behavior in the additive or extreme manufacturing.

Formation Mechanism of Eutectic Microstructure for Ca(Zr,Hf)O3/(Zr,Hf)O2 by Rapid Solidification Process at High Temperature

Abstract: Ca(Zr1-x,Hfx)O3/(Zr1-xHfx)O2 (x=0, 1/3, 0.5) eutectic film was prepared by rapid solidification process using high power laser irradiation method. The coating process was performed in an electric furnace at 1300°C. Solidified film with fine lamellar structure were obtained. When the Zr site was substituted with Hf, the lamellar spacing increased with the amount of the substitution. Separate from the solidification film prepared by laser irradiation, rapidly solidifying sample with x=0.1 composition was prepared using optical floating zone apparatus. The melt of the sample was free-fallen onto a copper dish. No film-like rapidly solidified sample was obtained. Hf ion was homogeneously solid-soluble in both phases of CaZrO3 and phase ZrO2.

Die steel design for additive manufacturing

A novel printable die steel was computationally designed and experiemtnally validated for selective laser melting (SLM), utilizing the advantages of the rapid solidification processes. During gas atomization, nanoscale TiN particles are intended to be insitu precipitated at 1790°C, nucleating δ-ferritic grains. Additionally, the chemical composition is adjusted to stabilize a complete δ-ferritic solidification via Scheil modeling to enhance the printability of the die steel. This work further introduces the concept of the matrix die steels aiming to dissolve solidification and primary carbides during solutionizing at a targeted temperature of 1100°C. Thus, the C-content is reduced to 1.4 mol.-% (0.3 wt.-%) compared to the benchmark H13 die steel with which contains 1.85 mol.-% (0.4 wt.-%). Even though a lower C-content is used, optimizing M2C driving force during tempering enables the die steel to achieve a peak hardness of 536 HV is achieved. Lastly, a superior thermal conductivity of 40 W m-1 K-1 is predicted at 450°C for the BCC matrix of the printable matrix die steel. The material design is based on thermo-chemical models interfaced with thermodynamic calculations as implemented in the Calculated Phase Diagram (CALPHAD) method.

Towards optimizing cooling rate, microstructure, and compressive strength in rapidly solidified Cu–20Fe alloy

There is currently interest in the development new Cu–Fe alloys with higher Fe content (>5 wt%), a low-cost element. In order to improve electrical, thermal and mechanical properties, there is a need to decrease the size of the Fe-rich phase and improve its distribution, whose possibilities rely on adding alloying third elements and heat treatments. However, the prospect of controlling the size of the phase through dendritic spacing control by means of rapid solidification processes may be feasible and deserves to be explored, as is the case in the present study. The following methods were employed to evaluate the round stepped cast samples of the Cu-20 wt% Fe alloy: centrifugal casting in a Cu mold, optical microscopy, CALPHAD, Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS), X-ray Diffraction (XRD), Vickers hardness, and compressive tests, in samples corresponding to different coarsening microstructures. Finally, dendritic growth is modelled using the Kirkwood equation. The results demonstrate a promising processing route with control of the secondary dendrite arm spacing (SDAS), whose methodology and modeling can serve as a basis for other alternative processes with the Cu–Fe alloys, allowing suitable size and distribution of Fe phase to be attained. It is further demonstrated that the Kirkwood model is able to match experimental SDAS in both slowly and rapidly solidified Cu–Fe samples. While Fe (BCC) is expected to increase strength, this is only slightly observed in the hardness results for smaller SDAS, as the loads are more superficial. In the case of compressive yield strength, SDAS in the observed range (1.4 μm–2.2 μm) is found to have no effect.

Bridging molecular dynamics and additive manufacturing: A study of Al-12 at% Si alloy solidification dynamics

This manuscript provides a detailed analysis of the molecular dynamics of the directional solidification process in Aluminum-Silicon (Al-12 % at Si) alloys, with a particular emphasis on applications in additive manufacturing. Utilizing molecular dynamics (MD) simulations, the study examines large systems containing 5–15 million atoms to investigate various facets of the solidification process. These include the dynamics of interface motion and the formation of Silicon (Si) precipitates. The research reveals significant variations in interface velocities and orientations across different thermal gradients and growth rates, underscoring the intricate interaction between thermal and solute flows in the microstructural development of Al-Si alloys. These findings are vital for comprehending and refining the solidification process in additive manufacturing, ultimately enhancing the mechanical strength and reliability of the final products. The paper highlights the critical role of microstructure control in printed metals and proposes future research directions, aiming to apply these insights to more complex alloy compositions and manufacturing contexts. In the concluding phase, the scikit-image library was employed to analyze dendritic formations in solidifying Al-Si alloys using MD simulations. This analysis delineates trends in dendritic count, spacing, perimeter, and area over time, offering essential perspectives on the solidification process and its implications for the alloy's microstructure and mechanical characteristics. The Si content in the Al-Si alloy used can be considered eutectic in the solidified structure. Si atoms are predominantly located at grain boundaries and precipitate regions. Coordination number analysis further confirms the presence of Si in these locations. This microstructure, characterized by a primary Al/Al-Si matrix and Si-rich eutectic regions, aligns with experimental observations in rapid solidification processes in additive manufacturing.

Evolution of short-range order and dynamics of medium-range order influence on the glass-forming ability of CuZrAg alloys

The glass-forming ability (GFA) of metallic glasses (MGs) is influenced by both short-range order (SRO) and medium-range order (MRO). However, experimentally examining the dynamic evolution of these microstructures across various time scales remains challenging. Therefore, this study employs molecular dynamics (MD) simulations to investigate the evolution of SRO and relaxation dynamics of MRO impacting on the GFA of Cu60Zr40-xAgx (x = 5, 10, 15, 20, 25) ternary alloys during their rapid solidification process. The GFA is characterized by the width of the supercooled liquid region, with Cu60Zr35Ag5 exhibiting the most prominent GFA among the five alloys. The reverse tracking method was utilized to analyze the inheritance and transformation of defective icosahedral clusters within the SRO. The defective icosahedral heritability and transformation rate are indicative of a more ordered and stable structure, significantly influencing the GFA. Furthermore, the decrease of Ag content leads to the increase of the average size of MRO clusters. The systems with larger MRO nanoclusters exhibit pronounced dynamic heterogeneity and a robust “cage effect”, thus hindering crystallization and promoting GFA. This study approaches GFA analysis from a microstructural evolution and dynamics perspective, aiming to provide theoretical backing for the discovery of alloys with superior GFA.

Enhanced 3D printing and crack control in melt-grown eutectic ceramic composites with high-entropy alloy doping

As a 3D printing method, laser powder bed fusion (LPBF) technology has been extensively proven to offer significant advantages in fabricating complex structured specimens, achieving ultra-fine microstructures, and enhancing performances. In the domain of manufacturing melt-grown oxide ceramics, it encounters substantial challenges in suppressing crack defects during the rapid solidification process. The strategic integration of high entropy alloys (HEA), leveraging the significant ductility and toughness into ceramic powders represents a major innovation in overcoming the obstacles. The ingenious doping of HEA particles preserves the eutectic microstructures of the Al2O3/GdAlO3(GAP)/ZrO2 ceramic composite. The high damage tolerance of the HEA alloy under high strain rates enables the absorption of crack energy and alleviation of internal stresses during LPBF, effectively reducing crack initiation and growth. Due to increased curvature forces and intense Marangoni convection at the top of the molt pool, particle collision intensifies, leading to the tendency of HEA particles to agglomerate at the upper part of the molt pool. However, this phenomenon can be effectively alleviated in the remelting process of subsequent layer deposition. Furthermore, a portion of the HEA particles partially dissolves and sinks into the molten pool, acting as heterogeneous nucleation particles, inducing the formation of equiaxed eutectic and leading primary phase nucleation. Some HEA particles diffuse into the lamellar ternary eutectic structures, further promoting the refinement of eutectic microstructures due to increased undercooling. The innovative doping of HEA particles has effectively facilitated the fabrication of turbine-structured, conical, and cylindrical ternary eutectic ceramic composite specimens with diameters of about 70 mm, demonstrating significant developmental potential in the field of ceramic composite manufacturing.

Molecular Dynamics Simulation on Solidification Microstructure and Tensile Properties of Cu/SiC Composites.

The shape of ceramic particles is one of the factors affecting the properties of metal matrix composites. Exploring the mechanism of ceramic particles affecting the cooling mechanical behavior and microstructure of composites provides a simulation basis for the design of high-performance composites. In this study, molecular dynamics methods are used for investigating the microstructure evolution mechanism in Cu/SiC composites containing SiC particles of different shapes during the rapid solidification process and evaluating the mechanical properties after cooling. The results show that the spherical SiC composites demonstrate the highest degree of local ordering after cooling. The more ordered the formation is of face-centered-cubic and hexagonal-close-packed structures, the better the crystallization is of the final composite and the less the number of stacking faults. Finally, the results of uniaxial tensile in three different directions after solidification showed that the composite containing spherical SiC particles demonstrated the best mechanical properties. The findings of this study provide a reference for understanding the preparation of Cu/SiC composites with different shapes of SiC particles as well as their microstructure and mechanical properties and provide a new idea for the experimental and theoretical research of Cu/SiC metal matrix composites.

Effects of Ti on the solidification and crystallization behavior of nanocomposite permanent material under different cooling rates

Effects of Ti on the crystallization behavior, phase composition, microstructure and magnetic properties of Nd2Fe14B/α-Fe dual-phase nanocomposite permanent magnet materials in different states were studied, respectively. The results show that Ti could affect the solidification and crystallization behavior of dual-phase nanocomposite materials by regulating the cooling rate during the rapid solidification process. When the cooling rate is slow, part of Ti atoms enters the soft magnetic phase α-Fe, and part forms the TiFe2 phase around the hard magnetic phase. Exchange coupling is enhanced. The maximum energy product and the remanence of the alloy are 10.54 MGOe and 8.34 kGs, respectively. When the cooling rate faster, Ti can stabilize another ferromagnetic ThMn12-type phase with a low coercivity and maximum energy product, which should be avoided. When the cooling rate is fast enough to form amorphous, Ti and Fe preferentially combine to form the TiFe2 phase during crystallization, which selectively inhibits the growth of the hard magnetic phase and the precipitation of the soft magnetic phase, resulting in a significant enhancement of coercivity to 12.82 kOe. By regulating the mechanism of Ti in the solidification and crystallization process, nanocomposite permanent magnet materials with varying magnetic characteristics can be obtained, offering a flexible approach to tailoring their performance according to specific application requirements.

Stabilizing metastable ferroelectric tungsten trioxide phase at room temperature via solvothermal synthesis and millisecond pulsed laser irradiation

Epsilon tungsten trioxide (ε-WO3) has drawn much attention for its unique gas sensing and ferroelectric properties. However, the strong metastability of ε-phase makes it extremely difficult to stabilize the phase at room temperature. For a long time, it was believed that the ε-phase can only be stabilized by rapid solidification processing. In this study, ε-WO3 was stabilized by employing solvothermal synthesis and subsequent annealing, with the help of Cr- and Ti-dopants. Structural characterization using XRD, Raman and TEM analysis revealed that the as-annealed powders are a mixture of ε-WO3 and γ-WO3 and the fraction of ε-WO3 is directly correlated with the Cr- and Ti-doping levels. Rietveld refinement suggests that the maximum obtainable fractions of ε-phase in as-annealed WO3 are ∼68 % for Cr-doping and ∼87 % for Ti-doping. The growth mechanism is that solvothermal synthesis produced Cr- and Ti-doped W18O49 and subsequent annealing resulted in phase transition from W18O49 to ε-WO3. The XPS analysis reveals the phase stabilization mechanism to involve the interstitial sites of WO3 being occupied by Cr3+ and Ti4+ dopants, resulting in structure distortions. The fraction of ε-WO3 can be further improved to almost 100 % by introducing kinetic constraints using pulsed laser irradiation to rapidly melt and solidify the WO3 (in several milliseconds). A viable solvothermal synthesis route for ε-WO3 and the feasibility to produce ε-phase via additive manufacturing are illustrated in this work.

Emergence of rapid solidification microstructure in additive manufacturing of a Magnesium alloy

Abstract Bioresorbable Mg-based alloys with low density, low elastic modulus, and excellent biocompatibility are outstanding candidates for temporary orthopedic implants. Coincidentally, metal additive manufacturing (AM) is disrupting the biomedical sector by providing fast access to patient-customized implants. Due to the high cooling rates associated with fusion-based AM techniques, they are often described as rapid solidification processes. However, conclusive observations or rapid solidification in metal AM — attested by drastic microstructural changes induced by solute trapping, kinetic undercooling, or morphological transitions of the solid-liquid interface — are scarce. Here we study the formation of banded microstructures during laser powder-bed fusion (LPBF) of a biomedical-grade Magnesium-rare earth alloy, combining advanced characterization and state-of-the-art thermal and phase-field modeling. Our experiments unambiguously identify microstructures as the result of an oscillatory banding instability known from other rapid solidification processes. Our simulations confirm that LPBF-relevant solidification conditions strongly promote the development of banded microstructures in a Mg-Nd alloy. Simulations also allow us to peer into the sub-micrometer nanosecond-scale details of the solid-liquid interface evolution giving rise to the distinctive banded patterns. Since rapidly solidified Mg alloys may exhibit significantly different mechanical and corrosion response compared to their cast counterparts, the ability to predict the emergence of rapid solidification microstructures (and to correlate them with local solidification conditions) may open new pathways for the design of bioresorbable orthopedic implants, not only fitted geometrically to each patient, but also optimized with locally-tuned mechanical and corrosion properties.

Microstructures, transformation temperatures and superelastic properties of the rapidly solidified (TiZrHf)50Ni25Co10Cu15 HESMAs

In this study, the effects of the rapid solidification process on microstructures, transformation behaviors and superelastic properties of the multi-component (TiZrHf)50Ni25Co10Cu15 (at%) high-entropy shape memory alloy (HESMA) were investigated. The as-spun (TiZrHf)50Ni25Co10Cu15 fibers were prepared by a rapid solidification process. The solution-treated (TiZrHf)50Ni25Co10Cu15 alloy bulk specimen consisted of a (NiCoCu)-rich matrix, (TiZrHf)2(NiCoCu)-type phase and carbide, while the as-spun fiber specimen consisted of (TiZrHf)-rich matrix and carbide. The (TiZrHf)2(NiCoCu)-type phase is dissolved in the matrix of as-spun fibers due to the rapid solidification process. The martensitic transformation start temperature of the (TiZrHf)50Ni25Co10Cu15 alloy increased from 53.5 °C to 91.5 °C after the rapid solidification process. Both the (TiZrHf)50Ni25Co10Cu15 alloy bulk and fiber specimens showed clear superelasticity and the total superelastic recovery strain increased from 4.6 % to 5.7% after the rapid solidification process.

Influence of ultrasonic parameters on microstructural refinement and defect elimination in ultrasound-assisted laser-based metal additive manufacturing

Acoustic cavitation, streaming, and energy absorption during solidification in ultrasound-assisted direct energy deposition additive manufacturing (DED-AM) have been reported to drive microstructural refinement, defect elimination, and mechanical property improvement. However, the influence of individual ultrasonic parameters such as frequency, amplitude, intensity, and sonication duration remains unknown. This is mainly because of challenges in real-time quantification of the influence of ultrasound on the rapid solidification and microstructural development processes encountered in ultrasound-assisted AM. High temperature and opaque molten metal confined within micro-length scale melt pools further challenge the characterization of ultrasound’s influence on microstructural development. Building upon our recent in situ observation of acoustic cavitation and streaming in sonicated laser-generated melt pools, this talk will highlight our efforts to correlate vibration frequency, amplitude, and intensity with grain size and texture of Al7075 alloy fabricated using ultrasound-assisted DED-AM. DED additively manufactured Al7075 is susceptible to solidification cracking. Therefore, this presentation will also showcase the influence of ultrasonic parameters on cracking suppression and defect elimination. In addition, the effect of sonication duration on microstructure will also be elaborated. Lastly, the presentation will showcase our future work toward upscaling ultrasound-assisted AM to large parts with complex geometries.

Characterization of microstructure and magnetic properties of 3D printed bonded magnets made by fused deposition modeling

Abstract Bonded magnets are composite materials consisting of polymer matrix and magnetic powders, prepared by rapid solidification processes from Nd-Fe-B alloys. They are synthesised by the compounding process on a twin-screw extruder, whereby, the finished products of complex shapes can be made from bonded magnets using injection moulding or 3D printing by fused deposition modelling method (FDM). The main advantages of 3D printing are the possibility to produce parts with complex geometries that are not possible with traditional manufacturing techniques and low-cost production of small batches. The aim of the research work was to identify the optimum processing parameters, which would give 3D printed bonded magnets characteristics similar to those produced by injection moulding. The characterization of the microstructure of bonded magnets was made on cryo-fractured, conventionally mechanically prepared and ion beam polished samples. The microstructures of bonded magnets were analysed by stereo, optical and scanning electron microscopy. Additionally, the influence of the 3D printing parameters on the magnetic properties has been examined. The results of the research work have shown that desired magnetic properties of 3D printed bonded magnets can be obtained by optimizing the thickness of the printed layer, printing speed and flowrate. In addition, it was revealed that selection of the materialographic preparation method plays a crucial step for correct microstructural characterization. Namely, the impropriate sample preparation results in artifacts that are mostly misinterpreted as microstructural defects (pores, cracks, non-adherent layers, etc.) accidently caused during 3d printing.