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60NiTi alloy is considered to be a promising material for specialized bearing and gear applications due to its high hardness, strength, and low modulus. However, fabricating 60NiTi through conventional processing methods is challenging due to the brittleness and poor workability. In this study, 60NiTi with high relative density was successfully fabricated directly from pre-alloyed powder through hot isostatic pressing. The effects of solution and aging treatments on microstructure and mechanical properties were systematically studied by advanced characterization techniques. The hot-isostatic-pressed 60NiTi showed low average hardness and elastic strain due to the formation of a soft Ni3Ti phase and B2 NiTi matrix. Solution treatment above 1000 °C dissolved the Ni3Ti phase and promoted the formation of nanoscale Ni4Ti3 precipitates, which significantly improved the hardness, strength, and elastic strain of 60NiTi. The formation of the Ni4Ti3 phase can be mainly attributed to the driving forces induced by the chemical supersaturation and mechanical stress concentration. Finally, the phase transformation mechanisms during heat treatment and compression test were discussed.

Background DDX52 is a type of DEAD/H box RNA helicase that was identified as a novel prostate cancer (PCa) genetic locus and possible causal gene in a European large-scale transcriptome-wide association study. However, the functions of DDX52 in PCa remain undetermined. The c-Myc oncogene plays a crucial role in the development of PCa, but the factors that regulate the activity of c-Myc in PCa are still unknown. Methods We determined DDX52 protein levels in PCa tissues using immunohistochemistry (IHC). DDX52 expression and survival outcomes in other PCa cohorts were examined using bioinformatics analysis. The inhibition of DDX52 via RNA interference with shRNA was used to clarify the effects of DDX52 on PCa cell growth in vitro and in vivo. Gene set enrichment analysis and RNA sequencing were used to explore the signaling regulated by DDX52 in PCa. Western blotting and IHC were used to determine the possible DDX52 signaling mechanism in PCa. Results DDX52 expression was upregulated in PCa tissues. Bioinformatics analysis showed that the level of DDX52 further increased in advanced PCa, with a high DDX52 level indicating a poor outcome. In vitro and in vivo experiments showed that downregulating DDX52 impeded the growth of PCa cells. High DDX52 levels contributed to activating c-Myc signaling in PCa patients and PCa cells. Furthermore, DDX52 expression was regulated by c-Myc and positively correlated with c-Myc expression in PCa. Conclusion DDX52 was overexpressed in PCa tissues in contrast to normal prostate tissues. DDX52 knockdown repressed the growth of PCa cells in vitro and in vivo. Deleting c-Myc inhibited DDX52 expression, which affected the activation of c-Myc signaling.

This study investigated the effect of annealing below glass transition temperature (Tg) on the microstructural characteristics, mechanical property, wettability, and electrochemical performance of activated combustion-high velocity air fuel (AC–HVAF)-sprayed Fe–Cr–Mo–W–C–B–Y amorphous coatings (ACs). Results showed that Fe-based ACs with a thickness of ~ 300 μm exhibited a fully amorphous structure with low oxidization. Originating from the reduced free volume, sub-Tg annealing increased the thermal stability, hardness, and surface hydrophobicity of Fe-based ACs. The enhanced corrosion resistance of sub-Tg annealed ACs in 3.5 wt% NaCl solution was attributed to the increased surface hydrophobicity and passivation capability. This finding elucidates the correlation between sub-Tg annealing and the properties of Fe-based ACs, which promotes ameliorating ACs with superior performance.

This article reports, for the first time, the application of Nb4C3Tx in the MXene series satisfying the formula of M4C3Tx in the field of hydrogen evolution reaction (HER). New etching parameters are proposed to obtain Nb4C3Tx with the largest c-lattice constant (3.165 nm) to date. Notably, Nb4C3Tx shows higher catalytic activity under the alkaline condition. Consequently, Nb4C3Tx has an overpotential of 398 mV at a current density of 10 mA cm−2, which is considerably less than that of other reported MXenes. Moreover, Nb4C3Tx has superior cycling performance and long-term stability in both acidic and alkaline environments. After 1000 cycles of CV, the overpotential of Nb4C3Tx clearly decreased by approximately 30 mV, and the current density significantly increased after the timing current test up to 50 h. This work demonstrates the excellent electrochemical performance that Nb4C3Tx can provide to benefit broad application prospects in energy fields.

Quasi-equiatomic CoCrFeMnNi high entropy alloy (HEA) has been in-situ alloyed by selective laser melting (SLM) from a blend of CoCrFeNi pre-alloyed powder and Mn elemental powder. The blended powder shows good printability with various SLM parameters and the as-built HEA samples achieve a reliable forming quality. Despite the slight evaporation of Mn, energy dispersive spectrometer mapping and X-ray diffraction results show that the as-built HEA has a homogeneous chemical distribution and presents a single face-centred-cubic (fcc) phase, indicating successful in-situ alloying. The study has verified the feasibility of using blended powder to prepare high-quality HEA by SLM.

To realize near net-shaping of hard-to-process intermetallics is an often challenging but critical issue to their wider industrial applications. In this work, we report that an intermetallic Ti–22Al–25Nb has been successfully fabricated by selective laser melting (SLM). The as-printed samples show a high room-temperature ultimate tensile strength ∼1090 MPa and excellent ductility ∼22.7%; both values are higher than most conventionally fabricated Ti–22Al–25Nb intermetallic. We clarify the mechanical performance achieved by detailed microstructure analysis, including dislocation and phase constitution. It is proposed that high-density dislocation networks significantly contribute to the strength and ductility, which are further enhanced by the favorable phase constitution, including the nano-scale O phase precipitates within the disordered β phase and disappearance of the brittle α2 phase in the microstructure. Phase evolution during solidification, particularly regarding the O phase's formation, has also been clarified using in-situ laser heating, high-temperature synchrotron X-ray diffraction and Scheil simulation. It is demonstrated that the O phase formation involves both displacive transition (B2 → B19) and chemical ordering (B19 → O). The metastable B19 phase (as an intermediate stage) may be formed by shearing cubic B2 phase along (110) [ 1 − 11 ] direction into an orthorhombic structure under high residual stress. Furthermore, a demonstrative part of turbine blade has been fabricated to highlight the importance of SLM in fabricating critical structural part like the hard-to-process intermetallics.

Inconel718 (IN718) superalloy is one of the most widely employed high-temperature materials. How to improve its working temperature limit is a challenging but rewarding task. In this study, we have proved that by simply mechanical blending pre-alloyed IN718 powder with elemental Al powder, one can successfully add extra Al to the IN718 alloy. The Al-added IN718 alloys developed by this study show homogenous distribution of Al in the as-printed microstructure produced by selective laser melting (SLM), and only a slight loss of the Al amount is detected due to SLM in situ alloying. Excellent relative density of > 99.5 pct has been achieved, and after the standard heat treatment, the IN718 + 0.5Al alloy shows good mechanical properties, achieving a fracture strength of ~ 1400 MPa and elongation of ~ 12 pct. Introducing an extra amount of Al into the IN718 alloy has also improved thermal stability, in which testing is conducted at 680 °C and held for 100 hours. Meanwhile, it is noted that by a new heat treatment approach, the Al-doped IN718 alloy achieves the best fracture strength at ~ 1600 MPa and elongation at ~ 10 pct. The implications of the study have been addressed.

Two-dimensional layered α-zirconium phosphate (ZrP) nanoplatelets with two distinguished sizes but similar aspect ratio were directly incorporated into polyamide 66 (PA66) by simple melt processing without using any surfactants. Through the electron microscopy analysis, the large ZrP nanoplatelets with ~ 1.33 μm in size and ~ 5.8 in aspect ratio exhibit a uniform dispersion in PA66 matrices at the filler loading up to 3 wt%, while the small ZrP nanoplatelets with an average size of ~ 230 nm and aspect ratio of ~ 6.2 tend to form large-scale aggregates in PA66 even at 1 wt% loading. Tensile testing results illustrate that the large ZrP nanoplatelets exhibit a better reinforcement effect in PA66 than the small ones. With the incorporation of 3 wt% large ZrP nanoplatelets, the PA66 nanocomposites exhibit an increase of ~ 10% in tensile modulus and ~ 14% in tensile strength as compared with the pure PA66. Pin-on-disc wear tests illustrate that the nanocomposites containing large ZrP nanoplatelets have better anti-wear properties than those prepared with small ZrP nanoplatelets. In specific, the PA66 nanocomposites containing 1 wt% large ZrP nanoplatelets show a ~ 43% decrease in friction coefficient and a ~ 59% reduction in the wear rate under the test condition of 40 N in load and 0.6 m/s in velocity. The mechanisms that are responsible for the mechanical and tribological enhancements in the PA66/ZrP nanocomposites have also been discussed.

Selective laser melting (SLM) is a laser-based additive manufacturing technique that can fabricate parts with complex geometries and sufficient mechanical properties. However, the optimal SLM process windows of metallic materials are difficult to predict, especially when exploring new metallic materials. In this paper, a universal and simplified model has been proposed to predict the energy density suitable for SLM of a variety of metallic materials including Ti and Ti alloys, Al alloy, Ni-based superalloy and steel, on the basis of the relationship between energy absorption and consumption during SLM. Several important but easily overlooked factors, including the surface structure of metallic powder, porosity of powder bed, vaporization and heat loss, were considered to improve the accuracy of the model. Results show that, to achieve near-full density parts, the energy absorption (Qa) by the local powder bed should be approximately 3–8 times greater than the energy consumption (Qc), and this finding applies to all materials investigated. The value of Qa/Qc highly depends on material properties, particularly laser absorptivity, latent heat of melting and specific heat capacity. Experiments on high-entropy alloy (CrMnFeCoNi) and Hastelloy X alloy, new metallic materials for SLM, have been further conducted to verify the model. Results confirm that the model can predict suitable laser energy densities needed for processing the various metallic materials without tedious trial and error experiments. Indications and uncertainty of the model have also been analyzed.

Background c-Myc, a well-established oncogene, plays an important role in the initiation and progression of various cancers, including prostate cancer. However, its mechanism in cancer cell remains largely unknown and whether there exist a deubiquitinase targeting c-Myc also remains elusive. Methods Bioinformatic analysis and shRNA screening methods were used to identify potential deubiquitinases that correlate with c-Myc gene signature. Cell proliferation and viability were measured by Cell-Counting-Kit 8 and colony formation assays. A mouse xenograft model of PC3 cells was established to confirm the function of USP16 in vivo. The interaction between USP16 and c-Myc protein was assessed by co-immunoprecipitation and protein co-localization assays. Immunohistochemistry staining was performed to detect the expression of USP16, Ki67, and c-Myc in xenograft tissues and clinical tumour tissues. Furthermore, the correlation between USP16 and c-Myc was confirmed by RNA sequencing. Results Functional analyses identified USP16, known as a deubiquitinase, was strongly correlated with the c-Myc gene signature. Depletion of USP16 was shown to significantly suppress the growth of PCa cells both in vitro and in vivo. Co-immunoprecipitation and ubiquitination assays confirmed that USP16 served as a novel deubiquitinase of c-Myc and overexpression of c-Myc significantly rescued the effects of USP16 disruption. Immunohistochemistry staining and RNA-seq tactics were further used to confirm the positive correlation between USP16 and c-Myc expression. Expression of USP16 in human PCa tissues was higher than that seen in normal prostate tissues and its high expression was found associated with poor prognosis. Conclusions USP16 serves as a novel deubiquitinase of c-Myc. Downregulation of USP16 markedly suppressed PCa cell growth both in vitro and in vivo. USP16 regulates PCa cell proliferation by deubiquitinating and stabilizing c-Myc, making it a potential therapeutic candidate for the treatment of PCa.

Magnesium alloys such as Mg–Ca and Mg–Zn–Ca are good orthopaedic materials; however their tendency to corrode is high. Herein we utilize selective laser melting (SLM) to modify the surface of these Mg alloys to simultaneously improve the corrosion behaviour and microhardness. The corrosion rate decreased from 2.1 ± 0.2 mm/y to 1.0 ± 0.1 mm/y for the laser-processed Mg–0.6Ca, and from 1.6 ± 0.1 mm/y to 0.7 ± 0.2 mm/y for laser-processed Mg–0.5Zn–0.3Ca. The microhardness increased from 46 ± 1 HV to 56 ± 1 HV for Mg–0.6Ca, and from 47 ± 3 HV to 55 ± 3 HV for Mg–0.5Zn–0.3Ca. In addition, good biocompatibility remained in the laser processed Mg alloys. The improved properties are attributed to laser-induced grain refinement, confined impurity elements, residual stress, and modified surface chemistry. The results demonstrated the potential of SLM as a surface engineering approach for developing advanced biomedical Mg alloys.

Additional file 3: Fig. S1. Films of long and short exposure in cycloheximide chase assay.

Additional file 1: Table S1. qPCR primers and shRNAs sequences.

β-solidifying TiAl alloys are considered as promising candidate materials for high-temperature structural applications. Laser-based additive manufacturing (LAM) enables the fabrication of components with geometrical complexity in near-net shape, leading to time and feedstock savings. In this study, a gas-atomized Ti-44Al-4Nb-1Mo-1Cr powder is used as a feedstock material for LAM. However, the LAM of TiAl alloys remains a challenge due to serious cracking during the printing process. To minimize the cracking, the optimization of the LAM processing parameters is essential. Hence, the effects of the LAM processing parameters on the cracking susceptibility and microstructure are studied here. Our experimental results show that the cracking susceptibility can be mitigated by increasing the laser power. Accordingly, the microstructure transforms from the dominating α2 grains to a near-lamellar microstructure with an increment in laser power, leading to a reduction in microhardness, even though it is still higher than that of its as-cast counterparts. It is concluded that changes in the laser power can directly tailor the microstructure, phase composition and microhardness of LAM-fabricated TiAl alloys.

Correlation between the feedstock powder and the as-printed products is well expected in laser powder bed fusion (LPBF). However, the inheritance/heredity relationship between the feedstock powder and the products remains broadly overlooked since most atomized powders are printed without any modification. This study addresses the inheritance issue through comparing the hydrogenation/dehydrogenation (HDH) Ti powder with the ball-milled (BM) Ti powder, as well as the respective as-printed samples. Rietveld refinement, focused ion beam, electron backscatter diffraction, and transmission electron microscopy are employed to characterize the microstructure; uniaxial tensile tests and fractographic observation are performed for the mechanical analysis; single-track finite element simulations are conducted to reveal the varied powder-bed properties. A “core-shell” powder structure has been generated through the ball milling modification. Nano-crystallites in the “shell” and stress-induced twins have brought significant grain refinement to the BM powder. A β-to-αm massive transformation has been observed in the samples printed using HDH powder, whereas the microstructure changes to fully-martensitic when using BM powder as the feedstock. Excellent mechanical performance (∼1000 MPa tensile strength with ∼20% ductility) have been achieved through inheriting the fine microstructure and oxygen content from the BM powder, which are induced by the powder modification process. This study has therefore unveiled the comprehensive correlation between the feedstock powder and the as-printed Ti, highlighting a novel methodology for developing additively-manufactured, cost-effective, and high-performance materials through tailoring the feedstock powder.

Graphene nanosheets (GNSs) strengthened AgCuTi composite filler (AgCuTiG) was used to braze C/C composite and Ti-6Al-4V. The effects of GNSs on the wettability of AgCuTiG filler on the C/C composite surface and the interfacial microstructure and mechanical properties of brazed joints were investigated. The results indicate that the addition of GNSs reduced the wettability of AgCuTiG. The interfacial microstructure of brazed joints evolved with the addition of GNSs, where Ti3Cu4 and TiCu4 were converted to TiCu and the thickness of the reaction layer adjacent to the base material decreased. The maximum shear strength of joints brazed at 0.3wt% GNSs was 23.3 MPa (880 °C/10 min). Further adding GNSs deteriorated the shear strength of the joints. Fracture of the joints occurred in the C/C composite substrate and the TiC layer adjacent to C/C composite. Keywords: Brazing, Graphene nanosheets, Mechanical properties, Microstructure, Wetting

Iron (Fe) is a potent β-stabaliser, capable to replace costly alloying elements such as V and Mo in forming cost-affordable, biomedical Ti alloys. Selective Laser Melting (SLM) is a mainstream additive manufacturing (AM) technology, competent in realizing near-net shaping of complex, quality parts. In this study, Ti-5Fe alloy was prepared by SLM using elemental powders of Fe and modified hydrogenated-dehydrogenated (HDH) Ti, aiming at providing a cost-affordable candidate biomedical Ti alloy. It is found that, under the “optimum printing parameters”, homogeneous distribution of Fe is possible by the in-situ alloying process. After further efforts in terms of impurity scavenging and heat treatment, the in-situ alloyed Ti-5Fe shows a combination of high strength, good ductility and good biocompatibility. The best mechanical properties achieved are ~865 MPa for tensile strength and ~12% for elongation. This study demonstrates the capability of laser in-situ alloying additive manufacturing in developing cost-affordable and high quality biomedical Ti materials.

Carbon/carbon (C/C) composite and Ti6Al4V alloy (wt%) were successfully brazed with graphene nanosheets strengthened AgCuTi filler (AgCuTiG). Graphene nanosheets (GNSs) with low CTE and high strength were dispersed into AgCuTi filler by ball milling. The interfacial microstructure was systematically characterized by varieties of analytical means including transmission electron microscopy (TEM). Results show that typical interfacial microstructure of the joint brazed at 880 °C for 10 min is a layer structure consisting of (Ti6Al4V/diffusion layer/Ti2Cu + TiCu + Ti3Cu4 + TiCu4/GNSs + TiCu + TiC + Ag(s,s) + Cu(s,s)/TiC/C/C composite). The interfacial microstructure and mechanical properties of brazed joints changed significantly as temperature increased. High temperature promoted the growth of TiCu and TiC phases, which were attached to GNSs. Meanwhile, the diffusion layer and primary reaction layers thickened as temperature increased, while the thickness of brazing seam decreased. The maximum shear strength of 30.2 MPa was obtained for the joint brazed at 900 °C for 10 min. GNSs decreased the thickness of brittle reaction layers and promoted the formation of TiCu and TiC phases in brazing seam, which caused the strengthening effect and decreased the CTE mismatch of brazed joints. The fracture modes are also discussed in this paper.

Ti2448 alloy fabricated by powder metallurgy using elemental powders of Ti, Nb, Zr and Sn exhibits good ductility but a high content of oxygen, and very limited work hardening in the tensile test. Its deformation mechanism is investigated by in-situ EBSD test conducted in an SEM equipped with a dynamic tensile stage. The results indicate that both dislocation slide and stress-induced phase transformation contribute to the plastic deformation of the alloy. Subsequent to yielding (after 3% of strain), β phase grains with preferential orientation " open=" 113 β / / X - a x i s tend to be transformed into α" martensite phase, which significantly reduces the plastic deformation caused by the dislocation slide and therefore leads to low work hardening.

Intermetallic γ-TiAl alloy has been considered as a promising structural material for high temperature use, owing to their advantages such as low density, high creep strength and good toughness. However, due to its intrinsic brittleness, γ-TiAl alloy could not accommodate the high thermal stress generated by fast cooling during laser-based additive manufacturing (LAM) process, resulting in cracking and distortion. To surmount the roadblock of low processability associated with γ-TiAl alloy, grain refinement technology was integrated to LAM. In the present work, LaB6 nanoparticles were identified and experimentally verified, for the first time, as an effective inoculant for LAMed γ-TiAl alloy. The results showed that the grain size of the as-printed alloy drastically decreased from 39.81 ± 9.12 µm to 1.5 ± 2.07 µm through 0.5 wt% LaB6 addition. Accordingly, the microstructural morphology transformed from coarse near-lamellar colonies into equiaxed and fine grains. The LaB6 inoculation treatment not only led to the fabrication of crack-free alloy but concurrently increases in compressive yield strength, ultimate strength and strain to fracture by 29%, 12.4% and 61.9%, respectively. Such an enhanced performance is comparable with or even better than the γ-TiAl alloys produced using conventional processing techniques.

Ti2AlNb (Ti–22Al–25Nb at.%, nominal composition) intermetallic is essential to aerospace industry from a weight reduction perspective, and brings a possibility of replacing some Ni-based superalloys. Despite evaporation of element Al (from its original composition 22.8 at.% to 18.5 at.%), selective laser melting (SLM) technology offers distinct advantages in fabricating Ti2AlNb intermetallic with superior room-temperature properties. A full understanding of corresponding heat treatment mechanism is the key to utilize well the SLM-prepared Ti2AlNb at high temperatures. This study aims to clarify the relationship between the microstructure and mechanical propensities of SLM-prepared then heat-treated Ti2AlNb, to ultimately achieve promising mechanical performances at high temperatures. For this research purpose, a series of heat treatments were conducted, and the corresponding microstructures, mechanical properties were systematic studied by advanced characterization techniques. Results show that the mechanical properties at both room and high temperatures depend on heat treatment adopted. The samples solution-treated at 950 °C and then aged at 700 °C show promising room and high temperature strengths due to the formation of acicular O, α2 and grain boundary α2 phases. However, their ductility was poor. Aging at 830 °C reduces the strength, but significantly improves the ductility due to the appearance of rodlike O phase and the increase of B2/β phase proportion. The alloy possesses promising strength and ductility (611 MPa, 10.0%) and high thermal stability at 650 °C. It is further demonstrated that the heat-treated Ti2AlNb possesses promising specific strength, even higher than that of as-cast Inconel 718 superalloy. The developed alloy, therefore, has a high potential for the industries requiring high-temperature performance and weight reduction.