Selective laser melting (SLM) is an attractive rapid prototyping technology for the fabrication of metallic components with complex structure and high performance. Aluminum alloy, one of the most ...pervasive structural materials, is well known for high specific strength and good corrosion resistance. But the poor laser formability of aluminum alloy restricts its application. There are problems such as limited processable materials, immature process conditions and metallurgical defects on SLM processing aluminum alloys. Some efforts have been made to solve the above problems. This paper discusses the current research status both related to the scientific understanding and technology applications. The paper begins with a brief introduction of basic concepts of aluminum alloys and technology characterization of laser selective melting. In addition, solidification theory of SLM process and formation mechanism of metallurgical defects are discussed. Then, the current research status of microstructure, properties and heat treatment of SLM processing aluminum alloys is systematically reviewed respectively. Lastly, a future outlook is given at the end of this review paper.
Nitrogen-containing carbon sphere with hierarchical porous structure is obtained through a facile thermostabilization and carbonization method of biomass-derivative sodium lignosulfonate. The ...synthesis route we proposed is cost-effective and environment-friendly without additional nitrogen precursor, activation or templating agent. The as-prepared carbon spheres exhibit high specific surface area of 1255–1939 m2 g−1 and moderate surface nitrogen content of 1.14–1.66 at.%. When assembling into supercapacitors with 7 M KOH aqueous solution as electrolyte, the carbon sphere shows superior gravimetric specific capacitance up to 276 F g−1 at 0.1 A g−1, high gravimetric energy density of 7.8 Wh kg−1 and power density of 6.2 kW kg−1, together with unprecedented cycling stability (99.5% capacitance retention after 10000 cycles). Notably, in 1 M SBPBF4/PC organic electrolyte, the carbon sphere based supercapacitor presents impressive gravimetric energy density of 34.3 Wh kg−1 and power density of 9.4 kW kg−1. These outstanding electrochemical performances suggest that the as-prepared porous carbon spheres should be a promising candidate for the field of energy storage.
Display omitted
In this study, the in-situ synthesized TiB/Ti-6Al-4Vceramic-matrix nanocomposites with greatly enhanced hardness and wear resistant property have been prepared via selective laser melting (SLM) using ...a simple mixture of microsized Ti-6Al-4V and TiB2 powders. In order to provide a valuable reference for fabricating TiB/Ti-6Al-4V parts with metallographic features, effects of reinforcement content on microstructure and mechanical properties have been systematically investigated. It is found that during SLM process, the additive particles TiB2 are totally transformed into need-like nanoscaled TiB phase, and the microstructure of composites is composed of mutual parallel strips architecture with TiB rich in some regions but lean in the other regions. The SLM-producedTiB/Ti-6Al-4 V composites exhibit superior nanohardness of 6.0 GPa, which is much higher than its traditional sintering counterpart. Moreover, the in-site synthesized TiB reinforcement can remarkably improve in the wear resistance properties, the wear loss of TiB-free sample is approximately 2 times than that of the sample with 3 wt% TiB2.
Display omitted
•In-situ synthesized TiB/Ti-6Al-4V nanocomposites have been prepared via SLM.•The need-like nanoscaled TiB phase formation and evolution mechanism during SLM is discussed in detail.•The interface orientation relationship between TiB and Ti matrix has been investigated.•The SLM-producedTiB/Ti-6Al-4V composites exhibit superior hardness and outstanding wear resistant property.
In order to enhance the strength and wear characteristics of stainless steel, Fe-based amorphous alloy with ultra-high strength was introduced to reinforce stainless steel through selective laser ...melting. The intrigued finding was that the amorphous alloy strengthened stainless steel exhibited an increased tensile strength from 819 MPa to 1090 MPa, a lower coefficient of friction (from 0.62 to 0.49) and a higher corrosion resistance. The enhancements of properties are contributed to the oxygen purification of Y element and solid solution of Co and Mo elements, as well as the grain refinement strengthen with the introduction of the amorphous alloy.
Display omitted
A novel crack-free Ti-modified Al-Cu-Mg alloy for SLM was developed here, based on the thermodynamic calculations of the crack susceptibility index and growth-restriction factor. We found that the ...introduction of Ti into the Al-Cu-Mg alloy effectively promoted the grain refinement and columnar-to-equiaxed grain transition as a result of the heterogeneous nucleation provided by Al3Ti precipitates. The hot tearing cracks were eliminated after Ti modification due to the formation of the homogeneous and fine equiaxed microstructure. We created a new high-strength Al-Cu-Mg-Ti alloy with a tensile strength of 426.4 MPa, yield strength of 293.2 MPa and ductility of 9.1%. This novel Ti-modified Al alloy with fine equiaxed grains and highly-enhanced mechanical properties offers a new compositional space for the printable lightweight material categories specifically for the SLM technique.
This paper proposes a novel price forecasting method based on wavelet transform combined with ARIMA and GARCH models. By wavelet transform, the historical price series is decomposed and reconstructed ...into one approximation series and some detail series. Then each subseries can be separately predicted by a suitable time series model. The final forecast is obtained by composing the forecasted results of each subseries. This proposed method is examined on Spanish and PJM electricity markets and compared with some other forecasting methods.
The Lishui Sag is on the southwest margin of the East China Sea Shelf Basin (ECSSB), which is located on the continental shelf of the East China Sea. The analysis of sedimentological signatures is ...based on 217 m (712 ft) of Paleocene cores showing a wide variety of lithofacies, sedimentary structures, ichnological data, seismic data, and log data. Eight lithofacies, nine typical ichnofabrics, and four ichnofacies combined with petrological, geophysical, and bioturbation information were identified as the key sedimentary facies characteristics for identifying three sedimentary systems in the study area. Eleven sedimentological facies are present in the three sedimentary systems: foreshore, upper shoreface, lower to middle shoreface, offshore transition, proximal fan delta front, distal fan delta front, wave-dominated delta front sand bar, wave-dominated delta front sand sheet, interbar, tide-influenced distributary channel, and tide-influenced interdistributary bay facies. The three sedimentary systems that were identified are fan delta, wave-influenced delta, and tide facies. Fan delta deposits are present in the southwest and northeast of the sag, with subaqueous fan delta front deposits dominating, whereas farther seaward successions are characterized by distal fan delta front deposits that are intensely bioturbated. Wave-dominated deltaic deposits occur mostly in the western and middle parts, where fluvial discharge in the delta front and prodelta have been repeatedly reworked by waves and formed some isolated bars distributed perpendicular to the source; these deposits are sparsely to intensely bioturbated. Tide facies develop locally and have been identified as distributary channels and interdistributary bay facies.
In order to protect the environment and check the emission of polluted gas, this article conducts research on energy saving and emission reduction technologies for marine diesel engines and their ...applications. In order to achieve this goal, we can improve and optimize combustion efficiency, improve combustion efficiency and combustion efficiency of diesel engines, and use new engines with higher and cleaner energy sources when using new energy sources with higher efficiency and less diesel, thus reducing pollution and achieving environmental protection objectives. The application of energy-saving and emission reduction technology in marine diesel engines can make them more efficient, improve efficiency, and facilitate combustion of diesel engines, reduce nitrogen oxides, recover heat generated by diesel engines, and improve energy consumption.
Recent research has shown that selected patients with initially unresectable hepatocellular carcinoma (HCC) are able to achieve conversion to resectable disease through systemic or local therapy. ...Combination regimens comprised of drugs with different mechanisms of action have shown better outcomes than single-drug or single-approach-based treatments; however, to date, combination regimens investigated as part of conversion therapy strategies have been two drug combinations with reported issues of relatively low surgical conversion and objective response rates. In this study, we investigated the efficacy and safety of triple combination therapy with angiogenesis inhibitors, programmed death-1 inhibitors and hepatic arterial infusion chemotherapy for surgical conversion of advanced HCC.
This was a single-center, retrospective, single-arm study of patients with unresectable HCC who received at least one cycle of triple combination therapy with an oral anti-angiogenic drug, programmed death-1 inhibitors and hepatic arterial infusion chemotherapy between August 2019 and August 2020. Endpoints included the overall response rate (ORR), surgical conversion rate, time to response and safety. Treatment response was assessed using the modified Response Evaluation Criteria in Solid Tumors (mRECIST) and RECIST v1.1.
In total, 34 patients were included in this study, of whom 25 completed treatment evaluation. The best ORR was 96.0% (24/25); 48.0% (n = 12) had a complete response, 48.0% (n = 12) had a partial response, and 4.0% (n = 1) had stable disease. The median time to response was 50.5 (95% CI, 31.02-64.00) days and the surgical conversion rate was 60% (15/25). Of the 25 patients, 56.0% (n = 14) received surgical resection and 28.0% (n = 7) had a pathologic complete response. Toxic side effects were manageable.
A triple combination therapy regimen of angiogenesis inhibitors, programmed death-1 inhibitors and hepatic arterial infusion chemotherapy showed significant therapeutic effect with an extremely high surgical conversion rate in patients with initially unresectable HCC.
This paper systematically investigated the effect of solution and artificial aging heat treatments on the microstructural evolution and mechanical properties of TiB/Ti–6Al–4V composites in situ ...fabricated by selective laser melting. The results showed that the fully martensite microstructure with TiB clusters of the as-built samples was transformed into lamellar α+β microstructure with TiB strips after solution heat treatment. With increasing the temperature, the α laths and TiB particles coarsened and the β volume fraction increased. After aging heat treatment, β volume fraction decreased and TiB had no obvious changes. A superior combination of the yield strength of (1146.8±28.2) MPa and even higher plasticity and ultimate compressive strength ((1680.1±18.3) MPa) than the as-built ones was obtained by solution heat treatment at 1000°C + water quenching and aging at 600°C for 6 h + air cooling.
Display omitted
PDF
