•The Ni-Co-Mn-Al alloys with good formability were successfully prepared by DLD.•The microstructure evolution of DLD Ni-Co-Mn-Al alloys was clearly clarified.•The factors affecting the phase ...transition of DLD Ni-Co-Mn-Al alloys were analyzed.•The Ni-Co-Mn-Al alloys with phase change and good mechanical property were obtained.
Ni-Co-Mn-Al magnetic shape memory alloys (MSMAs) has significant application prospects in driving, sensing, and refrigeration, however, its brittleness and difficulty in processing restrict the rapid development of applications. In this paper, the Ni-Co-Mn-Al alloy was prepared by laser direct deposition (DLD) and subsequent heat treatment (HT). The formability, microstructure, and properties of the samples were studied. The results show that the Ni-Co-Mn-Al alloy samples without obvious defects but with good formability were successfully prepared under the optimized DLD parameters. The deposited sample structure was composed of L10 martensite and 24.1 vol% γ(Co,Ni)Mn phase, and its compressive strength was 1785 MPa and the maximum compressive strain was 30.3%. Amounts of γ phases in the DLD samples hindered the martensitic transformation (MT). However, after HT at 850 °C for 16 h, the alloy sample structure was composed of L10 martensite and 3.5 vol% γ(Mn-rich) phase. The reduction of the γ phase promoted the MT so that the prepared Ni-Co-Mn-Al alloy be provided with characteristics of reversible MT. Meanwhile, the compressive strength of the sample reached 1295 MPa and the maximum compressive strain was 20.7%. The Ni-Co-Mn-Al alloy with representative phase transformation and good mechanical properties had been obtained.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
To improve the corrosion resistance and load-bearing performance of titanium alloy, the TiC/Ti based composite coating with good metallurgical quality was prepared on the surface of TC4 titanium ...alloy by using Diode laser, and the effect of TiC content on the microstructures and properties of TiC/TC4 cladding was studied. The microstructure and phase constitution of the coating were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD), the micro-hardness, corrosion resistance and the load-bearing performance of the coatings were evaluated. The results show that the cladding consists of TiC, TiC0.95, NiTi2 and α'-Ti, and the overall hardness of the coating fluctuates greatly. The micro-hardness in hard phases and in the heat affected zone are 1000-1500HV and about 437HV respectively. While the mass fraction of Ni coated TiC is not higher than 60%, higher corrosion resistance of claddings can be obtained with the increase of the mass fraction of Ni coated TiC, reaching a maximum at 60
Laser additive manufacturing alloy steel with good strength-ductility has important application prospects in the manufacturing of critical equipment parts. However, the poor matching of ...strength-ductility caused by high tensile strength and low elongation is a bottleneck problem that restricts the laser directed energy deposition (LDED) technology application. In this paper, based on the previous research on single physical field treatment, a new method to prepare alloy steel samples with better strength-ductility match by using compound physical field treatment (preheating/ultrasonic dual-field) to assist LDED alloy steel is proposed, thus solving the technical bottleneck problem of poor strength-ductility. The results show that the dual-field synergy has a more significant modulating effect on the densities, phase composition ratio, grain size, and strength-ductility matching properties of 24CrNiMoY alloy steel than the single field assistance by LDED. The density of the sample prepared with dual-field assistance was as high as 99.9%, and the phase compositions were ultra-fine crystalline lower bainite, granular bainite and residual austenite, with the average grain size refined from 0.46 μm to 0.26 μm. The ultimate tensile strength, elongation and strength-plastic product at break of the sample prepared by 360 W and 100 °C were (1058 ± 4.2) MPa, (13.8 ± 0.9)% and (14.6 ± 3.7) GPa%, respectively. A remarkable improvement of 12.3% in the strength-plastic product at break was achieved compared with the single ultrasonicated sample. The dual-field synergistic mechanism is the sufficient heterogeneous nucleation and cooling rate, which promoted the transformation of bainite morphology from lath to granular. The combined effect of the two aspects resulted in a satisfactory strength-ductility matching of the prepared alloy steel. This study will provide a promising theoretical and practical reference for the preparation of better strength-ductility matching alloy steel by dual-field-assisted LDED.
•A new method of preheating and ultrasonic composite-assisted LDED was constructed.•The evolution law regulating the LB to GB under dual-field synergy was elucidated.•The synergistic effect preparing strength-ductility matched sample was established.•The strength-plastic product was improved by 12.3% compared to ultrasonic field.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
For laser repairing the wear and corrosion failure parts, the effect of laser energy volume density (EVD) on the wear resistance and the corrosion resistance of 30Cr15MoY alloy steel coating prepared ...by the laser direct metal deposition (DLMD) was investigated. The 30Cr15MoY alloy steel coating composed of martensite, retained austenite and grain boundary precipitates was fabricated, exhibiting good quality without cracks and pores. A good metallurgical bonding between the 30Cr15MoY alloy steel coating and the substrate formed, the element dilution from substrate to coating was slight. The wear failure of coatings is a combination of abrasive wear, adhesive wear and oxidation wear, the sample has the lowest wear rate (6.49 × 10−6 mm3/N·mm) and the highest micro-hardness (768 HV0.2) when the EVD is 128 J/mm3. The wear resistance of the 30Cr15MoY alloy steel coating is mainly related to the solid solution content, the grain boundary type and the phase composition. The main corrosion failure of the DLMD 30Cr15MoY alloy steel coating is the pitting corrosion, and the sample with EVD of 128 J/mm3 displays the best corrosion resistance (Icorr: 0.43 × 10−6 A·cm2, Ecorr: −217.40 mV). The content of grain boundary precipitates is the main determining factor of the corrosion resistance, and the Cr-depleted regions surrounding the grain boundary precipitates are the preferential sites of the pitting corrosion. Besides, the corrosion resistance is also related to the solid-solution content of C and Cr and the grain boundary type. It is expected that this study could provide new material and wear and corrosion resistance theories for laser repairing short stress line rolling mill and other mechanical parts.
•New 30Cr15MoY alloy steel coating shows good quality without defects.•30Cr15MoY alloy steel coating exhibits good wear and corrosion resistance matching.•Wear and corrosion resistances increase first then decrease with increase of EVD.•Strengthening of solid solution, boundary and phase determines the wear resistance.•Cr-depleted region of GBP crucially affects the corrosion resistance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Laser direct energy deposition (LDED) of Ni-Co-Mn-Al-Y magnetic shape memory alloys (MSMAs) with high elastocaloric properties has important application prospects in solid-state refrigeration. ...However, because the microstructure of laser non-equilibrium metallurgy does not have reversible martensitic transformation, further regulating the microstructure of deposited samples through scientific post-heat treatment to obtain better properties is still a top priority. In this work, Ni-Co-Mn-Al-Y alloy samples were prepared by an optimized LDED process, and then the deposited samples were heat-treated with different temperatures. The results showed that the sample subjected to heat treatment with 550 °C × 3.5 h + 1100 °C × 20 h had maximum entropy change of the phase transformation, compressive properties, and elastocaloric effect. The compressive fracture strength was up to 1327 MPa, the maximum compressive strain was up to 26.2%, and an adiabatic temperature change was up to −4.3 K under the condition of rapid unloading. Characterization of the microstructure changes of the alloy under 11 cycles of compression revealed that the deformation mechanism was mainly planar sliding of dislocations in the martensite and dislocation cutting the γ(Y-rich) phase. The alloy prepared by the optimizing LDED and heat treatment process had better cycle stability and preliminary refrigeration capacity.
•The Ni-Co-Mn-Al-Y alloy samples had good compression properties, adiabatic temperature change, and cyclic compression stability.•The adiabatic temperature change, fracture strength, and maximum strain of the alloy prepared by the optimized process were improved by 126%, 7%, and 63%, respectively.•Successfully constructed a mechanism for enhancing the deformability of the prepared alloy by γ(Y-rich) phase.•The influences mechanism of microstructure on the martensitic transformation of LDED Ni-Co-Mn-Al-Y alloy were elucidated.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A novel Ni-Co-Mn-Al-Y magnetic shape memory alloy powder was prepared by the vacuum induction melting gas atomization method, and Ni-Co-Mn-Al-Y alloy samples were prepared by laser directed energy ...deposition (LDED) technique under different energy area densities and subsequent heat treatment. The effects of energy area densities and heat treatment on the grain size, microstructure, phase transformation, compressive strength, and elastocaloric response of the Ni-Co-Mn-Al-Y alloy samples prepared via LDED were clarified. The results showed that the characteristics of the prepared Ni-Co-Mn-Al-Y alloy powder met the requirements of LDED technology and the powder exhibited good laser printability. The microstructure of the samples before and after heat treatment was composed of martensite, austenite, and γ phase. The optimized energy area density sample of 150 J/mm2 demonstrated a good comprehensive performance with a compressive strength of 1241 MPa and an adiabatic temperature change of −1.9 K. This work can provide a useful reference for preparing high-performance magnetic shape memory alloys by LDED.
•A new Ni-Co-Mn-Al-Y alloy powder suitable for LDED was successfully prepared by the VIGA method.•The influence of energy area densities and heat treatment on the microstructure evolution of the prepared alloy was clarified.•The abnormal grain growth was related to the evolution of γ phase and subgrain boundaries during heat treatment.•The alloy with higher compressive strength and better adiabatic temperature change was successfully prepared.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Nickel-based K417G superalloy powder is the main material used in laser additive manufacturing (LAM) of aerospace engine turbine blades. In this study, K417G powder was prepared by the vacuum ...induction melting gas atomisation method (VIGA). Powder characteristics and microstructure were measured, and the properties of fabricated samples were studied. The results show that the powder mean particle size D
50
was 74 μm, flowability was 16.6 s/50 g, apparent density was 4.78 g cm
-3
, and the oxygen content of the powder was 0.015%. Powder and LAM sample microstructure consisted of γ, γ′, and carbide. The average microhardness was 410 HV, tensile strength was 1080 MPa, yield strength was 828 MPa and elongation was 13.52%. K417G superalloy powder prepared by VIGA method has potential for application in laser additive manufacturing.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
TG174.44; ...为了提高核燃料包壳Zr-1Nb合金的抗高温腐蚀性能,采用激光熔凝+真空退火热处理工艺对其进行表面处理.借助扫描电子显微镜(SEM)、X射线衍射(XRD)、拉曼等检测手段对锆管组织、成分及物相结构进行分析,使用探针式表面轮廓仪、显微硬度计和高压反应釜等仪器表征锆合金的粗糙度、硬度和耐蚀性.结果表明:经激光熔凝处理的锆管表面平整度提高;激光熔凝层物相主要由α-Zr和少量的m-ZrO2组成,且后续真空退火热处理没有改变锆合金的相组成;较高功率条件下进行激光熔凝显著降低锆管的高温耐蚀性能,而在较低功率进行激光熔凝工艺且辅助后续热处理的条件下,可以显著提高锆管的高温耐蚀性能;经激光熔凝处理后锆合金的显微硬度升高50～80 H V0.1,热处理后硬度相应减小,但仍高于原始样品.
Light-emitting diodes (LEDs) in the wavelength region of 535-570 nm are still inefficient, which is known as the "green gap" problem. Light in this range causes maximum luminous sensation in the ...human eye and is therefore advantageous for many potential uses. Here, we demonstrate a high-brightness InGaN LED with a normal voltage in the "green gap" range based on hybrid multi-quantum wells (MQWs). A yellow-green LED device is successfully fabricated and has a dominant wavelength, light output power, luminous efficiency and forward voltage of 560 nm, 2.14 mW, 19.58 lm/W and 3.39 V, respectively. To investigate the light emitting mechanism, a comparative analysis of the hybrid MQW LED and a conventional LED is conducted. The results show a 2.4-fold enhancement of the 540-nm light output power at a 20-mA injection current by the new structure due to the stronger localization effect, and such enhancement becomes larger at longer wavelengths. Our experimental data suggest that the hybrid MQW structure can effectively push the efficient InGaN LED emission toward longer wavelengths, connecting to the lower limit of the AlGaInP LEDs' spectral range, thus enabling completion of the LED product line covering the entire visible spectrum with sufficient luminous efficacy.
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