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The initial melting quality of a high-speed laser cladding layer has an important impact on its post-treatment and practical application. In this study, based on the repair of hydraulic support columns of coal mining machines, the influence of high-speed laser cladding process parameters on the quality of Fe-Cr-Ni alloy coatings was investigated to realize the accurate prediction of coating quality. The Taguchi orthogonal method was used to design the L25(56) test. The prediction models of the relationship between the cladding process and the coating quality were established using the Random Forest (RF) and AdaBoost (Adaptive Boosting, AB) algorithms, respectively. Then, the prediction accuracy of the two models was compared, and the process parameter features were screened for importance evaluation. The results show that the AB prediction model is more accurate than the RF prediction model and more sensitive to abnormal data. The importance evaluation based on the AdaBoost model shows that the scanning speed has a great influence on the height and surface roughness of the coating. On the other hand, the overlap rate is the most important factor in controlling the dilution ratio and near-surface grain size of high-speed laser melting coatings. In addition, the micro-hardness of the coating and the thermal effect of the substrate can be effectively enhanced by adjusting the laser power and scanning speed. Finally, it was verified that the AB prediction model could accurately estimate the quality indexes of the coating with a prediction error less than 6%. The results show that it is feasible to predict the quality of high-speed laser cladding with the AB algorithm. It provides a basis for the adjustment of process parameters in the subsequent quality control process of cladding. [ABSTRACT FROM AUTHOR]

The reaction of aluminum water to produce hydrogen is prevented by an alumina film. To prepare a kind of aluminum alloy with instant hydrogen production and high hydrogen yield, this paper investigates the effect of different Ga content and In–Sn ratio on the hydrogen production performance of aluminum alloy, and also observes the effect of hydrogen production at different temperatures. The composition, structure, and thermal properties are observed by Scanning Electron Microscope, X-ray diffraction, and differential scanning calorimetry. With different ratios of In and Sn, they appear as two intermetallic compounds, In 3 Sn and InSn 4. When Ga, In, and Sn were added to aluminum together, the hydrolytic properties of the Al-Ga-In-Sn alloys are greatly improved. The paper finally prepared an aluminum alloy with a hydrogen conversion rate of more than 98% and activation energy of 39.2 kJ/mol. Further the development and utilization of hydrogen energy are promoted. [Display omitted] • A high hydrogen yielding aluminum alloy prepared by melting was proposed. • The hydrolysis rate is proportional to the reaction temperature. • Effect of Ga content and In–Sn ratio on hydrogen production performance. • Effect of low melting point elements on the activation energy of aluminum alloys. • The activation energy of Al-3%Ga-5.25%In-1.75%Sn is 39.2 kJ/mol. [ABSTRACT FROM AUTHOR]

Ultra-high-speed laser cladding (UHSLC) not only offers an efficient solution to the limitations of conventional laser cladding but also aligns with the contemporary objectives of material conservation and efficiency enhancement in metal protective coatings. This study investigates the fabrication of CrFeCoNiMo 0.2 high-entropy alloy (HEA) coatings using UHSLC and traditional laser cladding (TLC) methods. Key aspects such as macroscopic forming quality, element distribution, dilution rate, grain morphology, hardness, and electrochemical corrosion properties of both UHSLC and TLC coatings are thoroughly examined. Notably, UHSLC-produced coatings, with their significantly reduced thickness ranging from 100 to 300 μm, demonstrate an impressively low substrate dilution rate compared to the 2–3 mm thickness of TLC coatings. The rapid solidification inherent in UHSLC leads to smaller grain sizes in the coating, resulting in enhanced hardness. Moreover, the UHSLC coating exhibits superior corrosion resistance, characterized by a lower maintaining-passivity current density in 1 mol/L H 2 SO 4 and a higher self-corrosion potential relative to TLC coatings. This work presents a novel approach, employing high-efficiency and low-cost laser-cladding technology, to minimize dilution in the matrix and improve the coating properties of HEAs. • There are no macroscopic and microscopic defects in HEAs prepared by UHSLC. • Uniform distribution of elements in ultra-thin coating of CrFeCoNiMo 0.2 HEA. • The CrFeCoNiMo 0.2 HEA nanocrystalline coating was synthesized by UHSLC. • Nanocrystalline CrFeCoNiMo 0.2 HEA coating exhibit excellent corrosion resistance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mg promotes the atomic diffusion of Al-Cu-Mg alloy. • The addition of Mg causes the alloy to generate more large-size Cu clusters. • The introduction of Mg lead to the formation of more FCC phases. • The enrichment of Cu intensified with the increase of Mg content. • Verified the consistency of simulation and experimental results. To analyze the mechanism of the Mg content on Cu precipitation in Al-Cu-Mg ternary alloy, the microstructure evolution of Al-5%Cu, Al-5%Cu-1%Mg and Al-5%Cu-2%Mg alloys during the solidification process was investigated by both the molecular dynamics simulation and solidification experiment methods. The simulated results demonstrate that the introduction of Mg accelerates atomic diffusion. And as the Mg content increases, more large-sized Cu agglomerates are formed in the solidified tissue, due to the Mg plays a connecting role in the process of Cu agglomerate formation. It is also found that the introduction of Mg results in the development of more FCC phases in the final tissue. The experimental results show that Cu elements are concentrated in the Al crystal boundaries, and the degree of Cu enrichment increases with the level of Mg content. The physical phase analysis shows that the final organization is primarily composed of the Al phase and Al 2 Cu phase, and both phases increase slightly with a higher Mg rate. The consistency between experimental and simulation results was verified by a comparative discussion of the Cu agglomerated and precipitated phases. It provides a theoretical basis for improving Al-Cu-Mg alloys' performance enhancement and structural optimization. [ABSTRACT FROM AUTHOR]

• Generation of hard phases and grain refinement in enhanced bionic units. • Bionic unit samples have good hard-soft alternating bionic structure. • Quantitative relation between distribution spacing and wear resistance is obtained. • Hard-soft bionic structure improves wear resistance by altering the wear pattern. • Adjusting the distribution spacing has a more positive effect on wear resistance. In this study, the biomimetic unit samples (BUSs) of hard-soft structure with different distribution spacings were successfully prepared by laser quenching biomimetic processing technique (LQBPT). Firstly, the microstructure, microhardness, tribological properties and wear surfaces were investigated. The BUSs had randomly oriented martensite and M 7 C 3 , and the grains were refined, resulting in favorable hard-soft structures. Compared to the untreated samples, the BUS at distribution spacing of 3 mm had excellent wear resistance. Its average friction coefficient and weight loss were reduced by 17.95 % and 40.0 %, respectively. Then, it was investigated the quantitative relationship between the distribution spacing and the wear resistance and its wear resistance mechanism. This improved wear resistance was attributed to hard-soft biomimetic structure. [ABSTRACT FROM AUTHOR]

The AlCoCrFeNi 2.1 eutectic high-entropy alloy (EHEA) has become one of the hottest research topics owing to its comprehensive mechanical properties. In this study, the AlCoCrFeNi 2.1 EHEA was fabricated via the laser powder bed fusion (L-PBF) technique, and the grain morphology, eutectic structure, mechanical properties, and deformation mechanism were investigated. The results indicate that the samples have superfine grains and nano-lamellar eutectic structures, attributable to the high cooling rate of the L-PBF process. Furthermore, the phenomenon of solute trapping was observed in the boundary of the FCC and B2 semi-cohesive phase in the nano-lamellar eutectic structure. Based on the special eutectic structure of the AlCoCrFeNi 2.1 EHEA prepared using the L-PBF technique, the samples exhibited an exceptional tensile strength of up to 1.6 GPa, accompanied by tensile ductility of over 9.5 %. The improvement of mechanical properties may be attributable to the Hall–Petch strengthening and back stress effect caused by refining the eutectic structure, whereas the growth of the nano-lamellar structure may be closely related to the solute-trapping effect. • Nano-lamellar EHEA with K–S type OR was prepared by additive manufacturing. • The L-PBF EHEA exhibited an exceptional tensile strength of up to 1.6 GPa. • The solute trapping phenomenon was observed at the boundary of nano-lamellar. [ABSTRACT FROM AUTHOR]

• Three stages of ice crystal formation in muscle tissue in this paper were analyzed. • The working principles and equipment of ultrasound-assisted freezing technique, high-voltage electric and magnetic field-assisted freezing technique, and liquid nitrogen freezing technique were discussed, respectively. • The future direction of cold chain storage and transport technology were analyzed. Low temperature environments can effectively inhibit the growth of microorganisms in raw meat products due to the reduced activity of enzymes, which is conducive to the long-term preservation of foodstuffs. At present, mainstream technologies include ultrasonic-assisted freezing, high-voltage electric and magnetic field-assisted freezing, and liquid nitrogen freezing technologies are widely used in the freezing process. In this paper, the freezing processes and devices for the fresh meat products were reviewed. The formation mechanism of ice crystals during the freezing of meat products was analyzed. The influence of the shape and size of ice crystals on their quality was studied. Also, the effect of different freezing processes and freezing device on the quality of meat products was studied. The key technologies regarding cold chain storage and transportation of meat products should move in the direction of intelligence, information, efficiency, and the unmanned. Finally, the key processes and device regarding freezing, cold chain, storage, and transportation were planned for the future development. [ABSTRACT FROM AUTHOR]

• La 2 O 3 improved the temperature gradient and reduces crack susceptibility. • La 2 O 3 promoted nucleation and grain refinement and increases dislocation density. • La 2 O 3 doping increased the hardness of the coating and improved the wear pattern. In this study, CoCrFeNiMoSi and CoCrFeNiMoSi + 0.5 % La 2 O 3 High entropy alloy (HEA) coatings were prepared by laser cladding. The microstructure was consisted mainly of body-centered cubic structure, face-centered cubic structure and intermetallic compounds of Si. The addition of rare earth La 2 O 3 resulted in the refinement and uniformity of the CoCrFeNiMoSi + 0.5 % La 2 O 3 HEA coating grains, leading to an increase in microhardness from 430 HV to 520 HV. Additionally, the friction coefficient decreased by 0.15 and the wear rate decreased by 2/3. These findings indicate that the appropriate addition of La 2 O 3 has significant potential in enhancing the friction and wear performance of HEA coatings. [ABSTRACT FROM AUTHOR]

[Display omitted] • The initial temperature is positively correlated with the diffusion coefficient. • The solid–liquid transition time of the system is affected by the cooling rate. • The lower the cooling rate, the easier the crystal structure formation. • The RDF analysis results are consistent with the visualization results. To analyze the various factors affecting the solidification organization of Al-Cu alloys, the melting and solidification processes of Al 0.67 Cu 0.33 alloy were simulated by the embedded atomic method (EAM) potential. It is found that the diffusion coefficient of the system keeps rising with the increasing initial temperature and relaxation time. It is a positive correlation between initial temperature, relaxation time and diffusion coefficient. The RDF analysis results are shown that as the cooling rate decreases, the crystal content of the solidified tissue increases and crystal structure characteristics of the system become more obvious. At the cooling rate of 1 × 1010 K/s, the percentage of system crystal compositions reaches 78.4%. The system shows obvious crystal structure characteristics. However, when the cooling rate was 1 × 1014 K/s, the crystalline content of the system is only 0.3% and shows obvious non-crystalline characteristics. It provides a theoretical basis for improving the properties and optimizing the microstructure of Al-Cu alloy. [ABSTRACT FROM AUTHOR]

To strengthen face-centered cubic structured high entropy alloys, this paper explores a new method of ceramic reinforced CoCrFeNiMo 0.2 high entropy alloy composite gradient coating. In this study, four sets of gradients were created by first preparing a pristine alloy coating without silicon carbide content on the substrate, followed by preparing composite coatings with varying silicon carbide mass fractions (8 %, 16 %, 24 %) on the pristine coatings. The coatings were then analyzed for their phase composition, microstructure, microstructure evolution process, and friction wear properties. The study reveals that the microstructure of the initial alloy coating consists of a single-phase face-centered cubic solid solution. It is observed that intragranular segregation occurs in the coating, resulting in the boundary enrichment of Mo and Cr elements. As the silicon carbide addition increases, the segregation behavior becomes more pronounced, and the generation of body-centered cubic phase is observed. The second, third, and fourth layers exhibit significantly higher average hardness, measuring at 594 HV, 722 HV, and 788 HV respectively. This can be attributed to the presence of body-centered cubic structure, carbide, and grain boundary strengthening effects. On average, the hardness of these layers is three to four times higher than that of the first layer. With an increase in the number of layers, the wear mechanism changes from adhesive wear to abrasive wear. The wear rates of the second, third, and fourth layers were all reduced by at least 87 % compared to the first layer. However, there were different forms of abrasive wear observed between these layers. The findings of this study have significant engineering implications. • The microstructural evolution of columnar grains to equiaxed dendrites was studied. • The high-density of dislocations enhances the diffusion of Mo and Cr elements. • The tissue shows phase separation act containing the BCC structure. • The shift behavior of the wear mechanism of the gradient structure was studied. [ABSTRACT FROM AUTHOR]

Solid-solution agglomerated ZrO 2 -based powders co-doped with Gd 2 O 3 , Yb 2 O 3 and Y 2 O 3 rare earth oxides were synthesized by solid-phase sintering and spray drying. The corresponding GYYZO coating was prepared by using atmospheric plasma spraying, while the 8YSZ coating was also prepared as a control group for the high temperature performance investigation. The high temperature structure and phase stability as well as the sintering resistance of both coatings were investigated by SEM, XRD, DSC, EPMA and TEM observations. The results showed that the 8YSZ coating began to undergo a phase transition of tetragonal (t) phase to monoclinic (m) after 50 h heat treatment at 1400 °C, while the GYYZO coating remained free of phase transition even heat-treated for up to 200 h, demonstrating a better phase stability. In addition, as an indicator of sintering resistance of the coating, the porosity of the 8YSZ coating decreased up to 90.1 % after 200 h heat treatment, while that of the GYYZO coating decreased only 20.6 %. The superior high temperature performance of GYYZO coating can be explained by the pinning effect of nano-pores on grain boundaries. The formation of nano-pores was associated with the evolution of defect clusters in the coating, which were facilitated by the substitution defects and oxygen vacancies created by the Gd Yb co-doping. During the heating process, these clusters migrated along with the grain boundaries and formed pearl-string-like nano-pores at the grain boundaries. The eventual formation of nanopores not only further inhibits grain boundary migration to reduce sintering, but also prevents the segregation of Y elements to hinder t-phase to m-phase transition. • GYYZO coating has excellent phase stability and sintering resistance at high temperature. • The nanopores of GYYZO coating have pinning effect on grain boundaries. • The pinning effect of nanopores can inhibit grain boundaries migration and Y elements segregation. [ABSTRACT FROM AUTHOR]

The AlCoCrFeNi high-entropy alloy coatings were prepared by laser cladding (LC) and reprocessed by laser remelting (LR). Laser remelting caused cracks on the coating surface, but the cracks of boronized laser remelting (LR-B) coating were significantly suppressed. Compared to the LR coating, the microhardness of the LR-B coating increased from 643 HV to 1008 HV, the friction coefficient decreased from 0.55 to 0.45, and the self-corrosion potential increased by 134 mV. The crack elimination contributed to the transition of 25% of the BCC phase to the FCC phase. The property enhancement was mainly due to the fine grain strengthening, dislocation strengthening, and Cr 2 B reinforced particles as reinforced phase. [Display omitted] • A trace amount of boron was doped in the protective gas during laser remelting. • The cracks of the boronized laser remelting (LR-B) coating were significantly suppressed. • With the addition of boron, the FCC phase and Cr 2 B were formed. • The Cr 2 B second-phase strengthening increased microhardness and wear resistance. • The Cr 2 B particles in the LR-B coating resulted in excellent corrosion resistance. To avoid cracking of the AlCoCrFeNi high-entropy alloy (HEA) coating during laser remelting (LR), a trace amount of boron (B) was doped in the protective gas. Compared to the LR coating, the cracks of the boronized laser remelting (LR-B) coating were significantly suppressed, the microhardness increased from 643 HV to 1008 HV, the friction coefficient decreased from 0.55 to 0.45, and the self-corrosion potential increased by 134 mV. The crack elimination mainly contributed to the transition of 25 % of the BCC phase to the FCC phase, and the property enhancement was due to the fine grain strengthening, dislocation strengthening, and Cr 2 B reinforced particles generation. This novel finding can be applied to other BCC structure HEA coatings for macroscopic crack control and optimization of wear and corrosion resistances. [ABSTRACT FROM AUTHOR]

To further strengthen the AlCoCrFeNi high-entropy alloy (HEA) coating prepared by high-speed laser cladding (HLC), laser remelting (LR) was chosen to reprocess it. The effects of LR on the topography, microstructure, growth orientation, phase distribution, and properties were investigated. It was revealed that there were a large number of liquid phase separation (LPS) zones in the HLC coating because of an ultrafast cooling rate. After LR, the LPS zones were eliminated. Compared to HLC coating, the microhardness increased from 622 HV to 762 HV, and the friction coefficient and the wear weight loss were reduced by 0.1 and 0.5 mg, respectively. In electrochemical testing, the self-corrosion potential increased by 45.9 mV and the self-corrosion current density decreased by one order of magnitude. Meanwhile, EBSD analysis indicated that the LPS zones were prone to recrystallization. The LPS zones were nickel-poor, low hardness, also BCC phase, and had a clearer (101) orientation. With the elimination of the LPS zones, the kernel average misorientation values were reduced, Taylor factor values and high angle grain boundaries were increased, and the average grain size was reduced from 2.43 μm to 2.12 μm. Eventually, for LR coatings, the combination of fine grain strengthening, solid solution strengthening, spalling reduction, and Cr element segregation resulted in better wear and corrosion resistances. The overall results show that a reasonable LR application can induce the microstructure of the HLC coating and improve its service properties. ● The AlCoCrFeNi high-entropy alloy coatings were prepared by high-speed laser cladding (HLC) and reprocessed by laser remelting (LR).● There were a large number of liquid phase separation (LPS) zones in the HLC coating. After LR, the LPS zones were replaced by fine equiaxed crystals.● The LPS zones were nickel-poor and low hardness, had a clearer (101) orientation, and tended to spall off in the wear test, causing a decrease in the overall wear resistance of the coating.● As a result of the elimination of the LPS zones, the microhardness and wear resistance of the LR coating were improved by solid solution strengthening and fine grain strengthening.● Appropriate undercooling and more high angle grain boundaries caused by LR provided a larger driving force for grain boundary segregation. The elemental content of Cr at the grain boundaries became higher, and the corrosion resistance of the LR coatings increased significantly. [Display omitted] • HLC led to a large number of the LPS zones in the AlCoCrFeNi HEA coating. • LR could successfully eliminate the LPS zones. • Recrystallization made the grains of the LPS zones coarse and soft. • The microhardness and wear resistance of the coating were improved by LR. • Higher Cr content at grain boundaries boosted corrosion resistance of LR coating. [ABSTRACT FROM AUTHOR]

The negative effects of thermal cycles in the process of additive manufacture present a challenge for the control of microstructure so as to fabricate the products with improved properties compared with conventional casting technique. In this work, AlCoCrFeNi 2.1 eutectic high-entropy alloy (EHEA) was prepared by laser metal deposition (LMD). Compared with conventionally cast EHEA samples, the LMD-fabricated EHEA samples showed significantly enhanced tensile strength (by 19.7%) and increased tensile ductility (by 56.4%). Such enhancement in tensile properties was attributed to the refinement of the uniformly distributed eutectic-structure, which improved the strain hardening/dislocation accumulation capability of the EHEA. The present work provides a new strategy to utilize both the high cooling rates of LMD and the eutectic-structure characteristics for forming refined homogeneous structures and thus achieving superior mechanical properties to those prepared by traditional processing techniques. [ABSTRACT FROM AUTHOR]

Al x CoCrFeNi (x = 0, 0.2, 0.45, 0.7 and 1) high entropy alloys (HEAs) have been successfully synthesized by laser melting deposition (LMD). It is found that the microstructure of LMD-CoCrFeNi HEA with increasing the content of Al has been transformed from a single face-centered cubic (FCC) phase to mixture of FCC + BCC duplex phases, and then to body-centered cubic (BCC/B2) phases. The addition of Al (Al 0.2 , Al 0.45 and Al 0.7) remarkably improved the yield strength σ 0.2 (from 138 MPa to 185 MPa, 262 MPa and 771 MPa) and the tensile strength σ t (from 634 MPa to 675 MPa, 863 MPa and 1171 MPa) of the samples, with the prize of plasticity decrease from 46% to 45%, 41% and 11% in tension. This work provides an approach of LMD-fabricated CoCrFeNi-based HEAs with different Al addition to accommodate the microstructure and mechanical properties, and insights into the correlation of mechanical properties with the solid solution strengthening or/and the precipitation of hardening phase. • Al x CoCrFeNi (x = 0, 0.2, 0.45, 0.7 and 1) HEAs have been prepared by LMD method. • The ΔH mix and VEC are used to predict the phase stability for LMD-fabricated HEAs. • The LMD HEA has been changed from a single FCC phase to BCC phase via Al addition. • With the increase of Al amount, σ 0.2 and σ t of the HEAs under the tensile and compression test have been obvious improved. [ABSTRACT FROM AUTHOR]

In the process of laser cladding forming, the season of process parameters had a fatal influence on the quality of cladding forming. In order to solve the problems of shape control difficulty, process parameter selection and long tnal-and-error experiment period, ANSYS parametric language APDL was used to establish a three-dimensional transient model to simulate the effects of laser power, scanning speed, powder feeding amount and spot diameter on temperature and cooling rate,and the process parameters with good forming quality were optimized. Combined with three groups of experiments, the width, height and depth of the layer and the crystal phase microstructure were measured to verify the feasibility of the numerical simulation. The results show that the optimum process parameters were laser power 1 400 W, scanning speed 10 mm/s, powder feeding rate 1.8 r/min,spot daameter 2 mm, respectively. The numerical simulation results of the width, height and depth of the layer were conssstent with the experimental results, and the forming quahty of the optimized process parameters was better than that of the control group. The research results of this paper pride a valuable reference value for the problem of shape control n laser adding of IN718 nickel base superalloy. [ABSTRACT FROM AUTHOR]

To enhance the strength of metastable austenitic stainless steel (ASS) sheet components, a novel method was proposed for the strengthening of a metastable ASS dome by a newly designed bulging device under deep cryogenic conditions. The load curves, Vickers microhardness, thickness distribution, and deformation law of formed dome components at room temperature (RT) and cryogenic temperature (CT) were discussed in detail. The strengthening mechanism of metastable ASS domes was elucidated by phase transformation, and the evolutions of grain boundary and dislocation at RT and CT, respectively. It is found that the strength of metastable ASS domes at CT increases with increasing strain. The strengthening effect of the metastable ASS sheet under biaxial stress state is significantly enhanced. Less martensite is generated at a low plastic strain, and the stability of the austenite phase is noticeably decreased under a large strain at CT. The dislocation distribution at RT is relatively uniform and is not accumulated at grain boundaries, while numerous dislocations at CT are apparently distributed near grain boundaries. The forming of metastable ASS domes at deep cryogenic temperatures is accommodated by both dislocation slip and martensitic transformation. Hence, the strength of metastable ASS thin-walled domes is significantly improved. (1) A novel method was proposed for the strengthening of metastable austenitic stainless steel (ASS) sheet by a newly-designed bulging device under deep cryogenic conditions. (2) Based on the quasi-in situ EBSD observations, the strengthening mechanism of metastable ASS domes was elucidated by microstructural phase transformation, and the evolutions of grain boundary and dislocation at room temperature (RT) and cryogenic temperature (CT). (3) Under the condition of low temperature biaxial stress, the strengthening effect of the metastable ASS sheet is significantly enhanced. Compared to RT, the maximum force increases from 105 to 182 kN at CT. The Vickers hardness increases to 393 HV at CT for the 20 mm dome, which is 38.9% higher than that at RT. (4) The stability of the austenite phase at a large plastic strain is noticeably decreased at CT. Martensitic transformation induced by a great strain is drastic. (5) The forming of metastable ASS domes at low cryogenic temperatures is microstructurally accommodated by dislocation slip and martensitic transformation. [ABSTRACT FROM AUTHOR]

An experimental study was conducted to analyze the undulated work-hardening behavior of S30408 metastable austenitic stainless steel at liquid nitrogen (LN 2) temperature. The flow stress curve, work-hardening process, strength, and ductility were studied by uniaxial tensile tests at both room temperature (RT) and −196 °C. Based on the scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM) observations, the effects of the cryogenic temperature and deformation degree on the dislocation evolution, phase transformation, slip behavior, and hardening behavior were analyzed. The cryogenic work-hardening mechanism regarding the initial hardening, undulated hardening, and unstable hardening throughout the whole tensile process was elaborated. The correlation between macroscopic work-hardening and microscopic martensitic transformation accompanied by a localized dislocation strengthening was illuminated. It was revealed that the high strength of the austenitic steel during the cryogenic deformation process resulted from the α′-martensite transformation accompanied by dislocation strengthening. A critical point of phase content was obtained at a strain of 0.095 at −196 °C. The undulated work-hardening at cryogenic temperature was mainly attributed to the alternating evolution of the α′-martensite and austenite phases with a non-uniform deformation mode. • The undulated work-hardening behavior of a metastable austenitic stainless steel was investigated at liquid nitrogen temperature. • The effects of cryogenic temperature and deformation degree on work-hardening behavior were analyzed. • The correlation between macroscopic work-hardening and microscopic martensitic transformation was illuminated. • An obvious critical point of phase content was obtained at a strain of 0.095 at −196 °C. [ABSTRACT FROM AUTHOR]

Homemade nano-agglomerated powders 8YSZ powders for PS-PVD were prepared by the spray drying, then calcination processes at four different temperatures (500 °C, 700 °C, 900 °C and 1100 °C) were carried out on the spray-dried powders. Checked by laser particle sizer, scanning electron microscope (SEM) and X-ray diffraction (XRD), the physical properties, microstructure and phase constitutions of the calcined powders were investigated. The results show that the size of powders calcined at 500 °C is increased relative to the spray-dried powder, whereas the powders calcined at 700 °C, 900 °C and 1100 °C possess smaller size. The binding force of the primary particles tend to rise with the increase of calcination temperature. When the temperature was up to 900 °C and above, it was found that the sintering neck indicating with strong binding was formed between the primary particles. In parallel, the powders underwent an m-ZrO 2 to t-ZrO 2 transition as the calcination temperature rose. It is also found that the PS-PVD prepared coatings which were obtained by using the above powders undergo a transformation from a feather-like to a dense laminate structure as the calcination temperature rises. It is noteworthy that the coating obtained by the powders calcined at 700 °C have a special three-layer composite structure of near dense surface layer, columnar intermediate layer and dense sub-layer. The composite structural coating has excellent adhesion and thermal shock resistance, with a bonding strength of 81MPa and no major spalling when water quenched 100 cycles at 1100 °C. [ABSTRACT FROM AUTHOR]