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ZrN and TiNiN nanolayers are alternately deposited on silicon substrate by magnetron sputtering. A series of ZrN/TiNiN nano-multilayer films with different Ni contents are prepared by varying the Ni:Ti volume ratio of the targets. The effects of Ni content on the microstructures and mechanical properties of ZrN/TiNiN nano-multilayer films are studied by X-ray diffractometer (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and nanoindentation instrument. The results show that with the increase of Ni content, the crystallization degree of ZrN phase first increases and then decreases. Besides, the hardness, elastic modulus and toughness of the films also increase first and then decrease with Ni content increasing. When Ni:Ti= 1:24, the ZrN/TiNiN nano-multilayer films obtain the highest hardness, elastic modulus and fracture toughness, which are 23.2 GPa, 317.8 GPa and 2.29 MPa·m1/2, respectively. This is mainly attributed to the best columnar crystal growth of the ZrN/TiNiN nano-multilayer film. The TiNiN layer changes into face centered cubic structure under the template of ZrN layer, and grows in coherent epitaxy with ZrN layer. ● A series of ZrN/TiNiN nano-multilayer films with different Ni contents are prepared by magnetron sputtering. ● When Ni:Ti= 1:24, the ZrN/TiNiN nano-multilayer films simultaneously obtain the highest hardness and fracture toughness. ● The high hardness and toughness are due to that the TiNiN layer grows in coherent epitaxy under the ZrN layer template. [ABSTRACT FROM AUTHOR]

• Mn-Cu alloys are fabricated by laser powder bed fusion based on mixed element powders. • The optimal processing windows for the dense Mn-Cu alloys is discovered. • The as-fabricated Mn-Cu alloys present good tensile properties. Mn-Cu alloys with high Mn contents have good damping capacity but poor workability and mechanical properties. In this research, laser powder bed fusion (LPBF) was applied to fabricate the Mn-Cu alloys (Mn 63 Cu 37 , Mn 73 Cu 27 , and Mn 82 Cu 18) based on mixed element powders. The printability, microstructure and mechanical properties of the as-fabricated Mn-Cu alloys were investigated through a series of characterization methods. The results indicate that the Mn-Cu alloys with high relative densities (99.76–99.85%) can be fabricated using the optimal processing parameters. The as-fabricated Mn-Cu alloys show higher strengths (537.5–589.6 MPa) and yield strengths (404.0–440.1 MPa) than those of commercial Mn-Cu alloys fabricated by conventional methods. The tensile strength presents an overall downward trend with increasing Mn content. Thus, LPBF can be considered as a promising method to fabricate Mn-Cu alloys with high Mn contents. [ABSTRACT FROM AUTHOR]

Four groups of newly developed Ni-based superalloy samples with different Zr contents were manufactured by Direct energy deposition (DED). This study focuses on the influence of Zr element concentration on microstructure and cracking formation mechanism in DED-processed Ni-based superalloy ZGH451. Although Zr content is low, it strongly affects the formation of the precipitated phase and hot tearing tendency. Measurement of the crack area showed that the crack density value increases with the Zr concentration. According to thermodynamic simulation results and microstructures observed, Zr microsegregation in the interdendritic regions and considerable amounts of Zr is present in oxides or carbides. Zr contributes to forming large-size carbides mainly due to zirconia providing nucleation sites and the dissolution of Zr. Simultaneously, the solidification has been retarded due to the continuous accumulation of large Zr atoms, which increases the γ-γ′ eutectic fraction. Moreover, Zr addition could effectively decrease the solidus temperature of ZGH451 alloys, leading to the critical liquid film at the end of solidification. Based on these results, staying below 0.05 wt% of Zr content to reduce the risk of hot tearing in additive manufacturing superalloy was proposed. • A newly designed ZGH451 superalloy with different Zr contents is successfully produced by direct energy deposition. • The effect of Zr contents on various precipitation phases and microstructure of ZGH451 superalloy is revealed. • The hot cracking formation mechanism in Zr-modified ZGH451 superalloy is systematically studied. • An upper limit for the Zr content of 0.05 wt% is proposed to optimize alloy design for AM superalloy. [ABSTRACT FROM AUTHOR]

The 2195 Al-Cu-Li alloy is widely utilized in the aerospace industry due to its lightweight nature and high strength. Consequently, gaining a comprehensive understanding of techniques to enhance its microstructural and mechanical properties is crucial for the consistent production of reliable and high-strength aerospace components. In this investigation, a pristine 2195 industrial ingot was subject to three distinct forging pretreatments: PT1, which involved a direct three upsetting and three stretching (3U3S) process; PT2, which combined double stage homogenization (DH) with 3U3S; and PT3, which involved DH along with six upsetting and six stretching (6U6S). Subsequent warm deformation and T8 aging treatment were applied to the pretreated forgings. The microstructure evolution during the processes and the final mechanical properties in three orthogonal dimensions were examined. The findings revealed that the combination of DH and multi-dimensional forging (MDF) facilitated the dissolution of non-equilibrium phases to a greater extent. Consequently, the main strengthening phase transformed from the T 1 + δ' phase observed in PT1 to the denser T1 + little θ' phase observed in PT2 and PT3 after T8 aging treatment. Notably, the tensile strength and yield strength of PT2 and PT3 specimens increased by 20–30 MPa in all three directions. Moreover, the MDF process accelerated the recrystallization behavior from PT1 to PT3, resulting in a gradual reduction in the average grain size of the pretreated samples from 356 µm to 186 µm. Following warm forging and T8 aging, the grains exhibited a finer and equiaxed structure. Additionally, the coarse phase was identified as the primary source of transgranular cracking. The coarse phases within the matrix became more homogeneous and finer from PT1 to PT3, with a gradual decrease in their area fraction. On the fracture surfaces, the aggregation of coarse phases diminished. Consequently, the elongation in the z-direction improved, and the elongation anisotropy and standard deviation decreased in all three directions for PT3 specimens. The findings presented in this study provide valuable insights into the high-performance manufacturing of Al-Cu-Li alloys. • The DH and doubling the strain of MDF both promoted the dissolution of non-equilibrium phases. • Combine DH treatment with MDF enhanced the precipitation kinetics of the T 1 phase, increasing the strength by 20–30 MPa. • The coarse phase was the main transgranular cracking sources, which was diminished gradually by the improved process. [ABSTRACT FROM AUTHOR]

In this work, the WC-Cr 2 (C, N)-Co nanocomposites were synthesized by using the one-pot carbothermal reduction nitridation hydrothermal precursor method. The preparation mechanisms, including phase and morphology evolutions, were investigated by differential thermal analysis (TG-DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and thermodynamic analysis. The results showed that phase evolution, with temperature increasing, follows the sequences of (amorphous phase, WO 2.72) → (CoWO 4 , WO 2.72 , WO 2 , CrWO 3) → (WO 2 , CoWO 4 , Co 6 W 6 C, CrWO 3) → (W 2 C, Co 3 W 3 C, WC) → (WC, W 2 C, Co 3 W 3 C) → (WC, Co, Co 3 W 3 C trace amount). Through comparing different heat treatment conditions, the powder particle size was more easily affected by temperature than holding time. The higher temperatures or longer time holding resulted in the aggregation of powder particles. Finally, WC-Cr 2 (C, N)-Co nanopowders with about 60 nm were obtained at 1050 °C for 1 h under the N 2 flow of 1 L/min with the oxygen content of 0.22 wt% and the free carbon content of 0.19 wt%. The TEM elements mapping revealed that Cr distributes uniformly with WC grains, Co and WC grains are combined well. The surface of WC-Cr 2 (C, N)-Co determined by XPS is mainly composed of W, Co, Cr, C, N, and O. The spark plasma sintering (SPS) sintered WC-Cr 2 (C, N)-Co composite shows a nanocrystalline microstructure with the average grain size ∼170 nm, and the excellent comprehensive mechanical properties with the Vickers hardness 1730 Kg·mm−2 and fracture toughness 11.5 MPa·m1/2, respectively. • The novel WC-Cr 2 (C, N)-Co nanocomposites were synthesized by using the one-pot carbothermal reduction nitridation hydrothermal precursor method. • The preparation mechanisms including phase and morphology evolutions, microstructure, chemical composition, and distribution were systematically investigated. • WC-Cr 2 (C, N)-Co nanopowders with about 60 nm were obtained at 1050 °C for 1 h under the N 2 flow of 1 L/min with oxygen content of 0.22 wt% and free carbon content of 0.19 wt%. • Through TEM and SEM characterization, the composition elements of the composite powder were evenly distributed, Co and WC grains are combined well. • Nano-WC-Cr 2 (C, N)-Co cemented carbides (∼ 170 nm) showed excellent comprehensive mechanical properties with Vickers hardness and fracture toughness of 1730 Kg mm−2 and 11.5 MPa m1/2, respectively. [ABSTRACT FROM AUTHOR]

The 2195 Al-Cu-Li alloy is widely utilized for the fabrication of key aerospace vehicle components; hence, an in-depth understanding of its hot deformation behavior is essential for consistently achieving high-performance products. In this study, isothermal compression tests were performed on 2195 Al-Cu-Li alloy ingots in the temperature and strain rate ranges of 250–500 °C and 10−3-1 s−1, respectively. A processing map was established to predict the workability under different conditions. The corresponding microstructures were examined to reveal their hot deformation mechanism. Results demonstrated that the processing map was divided into four distinct domains. The unstable zone was located in the 250–375 °C/10−1.5-1 s−1 and 250–275 °C/10−2.5–10−1.5 s−1, temperature/strain rate regimes, in which deformation bands and flow localization were observed. The deformation bands blocked dislocations and compromised the dynamic recrystallization (DRX) behavior, hence damaging the microstructure. Further, large coarse T 1 phases precipitated in the 325–410 °C/10−2.5–10−3 s−1 regime, which led to the formation of heterogeneities in the microstructure, corresponding to a minimum workability in the processing map. The optimal hot-working domain for the 2195 alloy was determined to be 460–500 °C/10−3–10−2 s−1, and the dominating hot deformation mechanisms were DRX and dynamic recovery (DRV). Specifically, continuous and discontinuous DRX behaviors dominated in the 300–400 °C/10−3 s−1 and 450–500 °C/10−3 s−1 regimes, respectively. DRX gradually weakened as the strain rate increased at 500 °C. Further, the weakening of DRX was only minimally affected by temperature at 400–500 °C during high-speed deformation (1 s−1). The results reported herein can provide valuable insights into the hot working of Al-Cu–Li alloys. • A processing map (PM) was established to accurately predict the hot deformation behavior of the 2195 alloy. • Deformation bands and flow localization were the main microstructure response in the unstable domain. • Large coarse T 1 phases precipitated in the precipitation sensitive domain, leading to heterogeneity deformation. • The optimal hot working domain was 460–500 °C/10−3–10−2 s−1, which was dominated by DRX and DRV. • Within the 300–400 °C/10−3 s−1 regime, CDRX was the main DRX mechanism, whereas DDRX predominant at 450–500 °C/10−3 s−1. [ABSTRACT FROM AUTHOR]

As an additive manufacturing technology, Fused Deposition Modeling and Sintering (FDMS) technology can give diamond tools some creative structures to be applied in more fields. To explore the influence of diamond parameters on diamond tools manufactured by FDMS, copper-tin-diamond composite samples with different diamond concentrations and particle size were prepared by FDMS technology in this paper. During the study, the morphological characteristics of diamond particles inside the samples during the debinding and sintering process are summarized and the influence of diamond parameters on the mechanical properties and structure of the samples was further explored. These influence laws were also verified by cutting experiments. The results show that most diamond particles are in an incomplete coating state because of the volatilization of the binder. Meanwhile, a higher concentration of diamond will lead to more pores and cavities in the samples; and the cavities can be connected to form a large area of cavity zone by the print layer, thereby resulting in a serious loss in the performance of the samples. On the other hand, a small diamond particle size can lead to agglomeration of particles. Subsequently, this will result in void generation and regional weakening of the holding ability. However, agglomeration and some pores or cavities will increase the wear of the matrix, expose more diamond particles, and finally improve the cutting efficiency of the dicing blades when cutting sapphire crystal. Excessive wear may reduce the life of the diamond tool, but improved of sharpness can be better applied in the field of precision machining. • Higher concentration of diamond will lead to more pores and cavities. • The cavities will be connected and form a cavity zone due to FDMS process. • Agglomerates can lead to void generation and weakening of the holding ability. • Increased diamond concentration amplifies the effect of particle size on agglomeration. • Appropriate diamond parameters can prevent crack propagation. • Characteristic endowed by FDMS will improve the cutting efficiency of tools. [ABSTRACT FROM AUTHOR]

• Co-based diamond composites were separately fabricated via the FDMS and the powder hot-pressed sintering technology. • There is a certain difference in the overall performance of the two kinds of specimens. • The Co-based samples fabricated by FDMS form a special coating state for diamond particles. • The Co-based samples fabricated by FDMS have defects of high porosity inside the matrix. • The reduction of knife-cut features can represent the improvement of density and holding ability of the FDMS sample. Fused deposition molding and sintering (FDMS) technology has the characteristics of low cost and low damage to diamonds. In order to explore more possibilities of additive manufacturing diamond tools, FDMS technology was considered to manufacture Co-based diamond composites at different temperatures in this paper. Also, specimens of Co-based diamond composites were manufactured under the same sintering process by using the powder hot-pressed sintering technology. And the matrix microstructure and properties of the specimens made by those two different technologies were analyzed and compared. The results show that a lot of porosity defects were developed inside the specimens manufactured by FDMS. This is because of the specific process characteristics of FDMS. Also, the matrix forms a special coating state for diamond particles due to the binder system used in this study, which causes some diamond particles to suffer slight thermal damage. These all will reduce the density and holding ability of the FDMS specimens. However, when the sintering temperature increases from 800 °C to 880 °C, the performance loss of FDMS samples caused by the porosity defects gradually decreases, thereby reducing the performance difference when comparing with the powder hot-pressed sintering specimens. In addition, the matrix structural uniformity of the FDMS specimens is significantly improved during this process, and the fracture feature changes from intergranular fracture to transgranular fracture. But there is still a certain difference in the overall performance of the two kinds of specimens at the optimal sintering temperature. Therefore, the further optimization of FDMS process parameters and binder system is of great significance for the application of FDMS in diamond tools. [ABSTRACT FROM AUTHOR]