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Upon 98% reduction cold-rolling, a single layer AA3003 foil material of 115 μm thick was intermediately annealed at 300–420 °C/1-8 h, and the preferred temperature and time of the intermediate annealing for the laminated AA4343/AA3003/AA4343 composite foil material were determined. All of these samples were cold rolled by 40% to 70 μm thick and finally annealed at a temperature in the range of 300–550 °C for 1–9 h. Their sagging resistance and microstructure were investigated using simulated brazing treatment, optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). For the single layer AA3003 foil, the sagging distance decreased first and then increased with increasing intermediate annealing temperature, and the lowest sagging distance corresponds to the coarsest grain in the recrystallized sample. After the final annealing for the single layer, the sagging distance decreased monotonously. For the laminated foil subjected to the final annealing, the sagging distance curves decreased first and then increased with increasing annealing temperature and time. The improvement of sagging resistance was attributed to the recovery of two types of materials during annealing process. The deterioration of the sagging resistance in the laminated foils was due to the corrosion in the brazing process, resulted from the Si diffusion from the cladding layer into the core layer. It is the coarse grains, few dislocations and minimal diffusion of Si that are crucial for improving the sagging resistance of the laminated foils.

The effects of Nb and Ni contents on the precipitation of the Ni16Nb6Si7-G phase and the resulting hardening behavior in Fe–20Cr ferritic alloys were systematically investigated using micro-hardness, electron microscopy, and atom probe techniques. The results demonstrate that an optimal Nb content of ∼0.75 wt. % promotes the precipitation of the Ni16Nb6Si7-G phase, leading to a maximum micro-hardness of approximately 430 H V when aged at 560 °C for 24 h. Excess Nb content (>0.75 wt. %) introduces the Fe2Nb-Laves phase at grain boundaries and within the grains, which competes with the G-phase for precipitation. Conversely, an increase in Ni content effectively raises the dissolution temperature of the Ni16Nb6Si7-G phase to approximately 850 °C. The austenite phase begins to form when the Ni content exceeds 4 wt. %. Finally, the strengthening effect of the Ni16Nb6Si7-G phase and its underlying competition precipitation with the Fe2Nb-Laves phase as well as the possible benefit of inducing austenite phase was discussed in the context of developing 20Cr ferritic alloys with high strength and good ductility. These findings provide valuable insights into the influence of Nb and Ni contents on the microstructural evolution and mechanical properties of the newly developed 20Cr alloy, which may be helpful in guiding the design of high performance ferritic alloys by optimizing composition and heat treatment processes.

The influence of aging treatments on the dynamic mechanical response of the 7B52 laminated alloy, and the correlation between the SHPB impact performance of 7xxx laminated aluminum alloy and its base alloys were investigated. Through adjustments the aging temperature and duration, alloys were obtained under underaged, peak-aged, and overaged conditions. Subsequently, Split Hopkinson Pressure Bar (SHPB) impact tests were conducted. The results indicate that the SHPB impact strength of the base alloy is higher in the peak-aged state compared to the under-aged and over-aged states. Additionally, as the aging temperature decreases, the alloy's impact toughness increases. The impact strength of laminated plates can be assessed by computing a linear weighted sum of the impact strength of individual alloys. The impact toughness of laminated aluminum alloys is notably influenced by the disparity in impact strength between 7A52 and 7A62 alloys. When the difference in impact strength between base alloys is small, the deformation of laminated plates is uniform, which can enhance the additional impact toughness of laminated aluminum alloys. Finally, an impact performance prediction formula for laminated plates is provided through linear fitting.

Background: Using targeted liposomes to encapsulate and deliver drugs has become a hotspot in biomedical research. Folated Pluronic F87/D±-tocopheryl polyethylene glycol 1000 succinate (TPGS) co-modified liposomes (FA-F87/TPGS-Lps) were fabricated for curcumin delivery, and intracellular targeting of liposomal curcumin was investigated. Methods: FA-F87 was synthesized and its structural characterization was conducted through dehydration condensation. Then, cur-FA-F87/TPGS-Lps were prepared via thin film dispersion method combined with DHPM technique, and their physicochemical properties and cytotoxicity were determined. Finally, the intracellular distribution of cur-FA-F87/TPGS-Lps was investigated using MCF-7 cells. Results: Incorporation of TPGS in liposomes reduced their particle size, but increased the negative charge of the liposomes as well as their storage stability, and the encapsulation efficiency of curcumin was improved. While, modification of liposomes with FA increased their particle size, and had no impact on the encapsulation efficiency of curcumin in liposomes. Among all the liposomes (cur-F87-Lps, cur-FA-F87-Lps, cur-FA-F87/TPGS-Lps and cur-F87/TPGS-Lps), cur-FA-F87/TPGS-Lps showed highest cytotoxicity to MCF-7 cells. Moreover, cur-FA-F87/TPGS-Lps was found to deliver curcumin into the cytoplasm of MCF-7 cells. Conclusion: Folate-Pluronic F87/TPGS co-modified liposomes provide a novel strategy for drug loading and targeted delivery.

Microstructural evolution and its effect on microhardness and Young's modulus of Ti–6Zr–4Fe alloy solution and aging treated at different temperatures were studied. The α phase transformed into β phase completely at 860 °C, meanwhile, the athermal ω phase was found at 860 °C and it resulted in a higher Young's modulus. The ω phase content increased from 250 °C to 400 °C, and the content decreased with further increase of aging temperature, there were only α phase and β phase at 600 °C. The phase transformation sequence was β → ω + β → ω + α + β → α + β during aging treatment. The microhardness increased from 315 HV to 492 HV due to the element solution strengthening and phase transformation strengthening. The peak microhardness of Ti–6Zr–4Fe alloy aged at 400 °C reached 652 HV. The formation of ω phase resulted in the increase of microhardness and Young's modulus in Ti–6Zr–4Fe alloy.

Aging behavior and phase transformation of Al–5Zn–1Mg–1Cu(-Si) alloys under different isothermal temperatures were investigated using transmission electron microscope (TEM) and mechanical tests. The aging temperature and Si addition significantly influenced to the types of precipitated phases and mechanical properties of the Al-Zn-Mg-Cu alloys. Adding Si in this alloy changed the precipitated phases from T' and η' phases to the dual-sized η and GPB-II phases. With increasing isothermal aging temperature, more GPB-II phases formed in alloys with the same composition, effectively improving the microhardness and mechanical properties. When aging at 150°C, 0.5wt%Si-containing alloy reached the highest peak hardness of about 150HV and maintained stable hardness, while an alloy without Si only reached 120HV and later declined by 15HV. The tensile strength and yield strength of the 0.5wt%Si-containing alloy were higher than those of non-Si alloy by 132 MPa and 165 MPa, increasing 51% and 90%, respectively. This result was due to the presence of fine and dispersed 4-8 nm GPB-II phases in 0.5wt%Si-containing alloy. The GPB-II phase had a core-shell structure, with the core region mainly enriched in Mg and Si, and the shell region mainly enriched in Cu and Zn. Compared with the stability of T' and η' phases, this core-shell structure of GPB-II effectively inhibited its growth and beneficially maintained a smaller-sized GPB-II phase. The strengthening effect of GPB-II phase was better than that of η or T phases when aging at 150°C or 200°C. The mechanical properties of high Zn/Mg ratios Al-Zn-Mg-Cu alloys can enhanced by adding Si.

Aim: Folate-conjugated Pluronic F87-poly(lactic-co-glycolic acid) block copolymer(FA-F87-PLGA) was synthesized to encapsulate anticancer drug Paclitaxel (PTX) for targeteddrug delivery. To further improve the curative effect, D-α-tocopheryl poly(ethylene glycol) 1000succinate (TPGS or Vitamin E TPGS) was added to form FA-F87-PLGA/TPGS mixed NPs. Methods: FA-F87-PLGA was synthesized by the ring-opening polymerization, and the structurewas characterized. PTX-loaded nanoparticles were prepared with the nanoprecipitation method.The physicochemical characteristics were studied to determine the appropriate dose ratio of theFA-F87-PLGA to TPGS. The cytotoxicity against Ovarian Cancer Cells (OVCAR-3) was determinedby MTT assay. The Area Under the Curve (AUC) and half-life were measured in the in vivopharmacokinetic studies. Results: Based on the optimization of particle size and embedding rate of PTX-loaded mixed NPs,the appropriate dosage ratio of FA-F87-PLGA to TPGS was finally determined to be 5:3. Accordingto in vitro release studies, the cumulative release rate of PTX-loaded FA-F87-PLGA/TPGSmixed NPs was 92.04%, which was higher than that of nanoparticles without TPGS. The cytotoxicitystudies showed that the IC50 value of PTX-loaded FA-F87-PLGA/TPGS decreased by 75.4 timesand 19.7 times after 72 h treatment compared with free PTX injections and PTX-loaded FA-F87-PLGA NPs, respectively. In vivo pharmacokinetic studies indicated that FA-F87-PLGA/TPGSmixed NPs had a longer drug metabolism time and a larger Area Under the Curve (AUC) comparedwith free PTX injections. Conclusion: FA-F87-PLGA/TPGS mixed NPs are potential candidates for targeted drug deliverysystems.

ABSTRACTThe microstructural evolution of two model alloys, Fe–NiAl and Fe–NiAl–Mn, during aging at 500°C was investigated using atom probe tomography (APT). Vickers micro hardness measurements showed that the addition of Mn increased the hardness and decreased the time to reach the peak hardness. Both alloys exhibited a softening process at the initial stage of aging. The APT results showed that adding Mn increased the number density of NiAl nanoparticles significantly, and Mn atoms partitioned into the NiAl nanoparticles, occupying the Al sites preferentially. The precipitation of NiAl nanoparticles was accelerated by the addition of Mn because Mn increased the nucleation driving force for NiAl precipitates and reduced the strain energy for the nucleation.

The microstructural evolution of two model alloys, Fe–NiAl and Fe–NiAl–Mn, during aging at 500°C was investigated using atom probe tomography (APT). Vickers micro hardness measurements showed that the addition of Mn increased the hardness and decreased the time to reach the peak hardness. Both alloys exhibited a softening process at the initial stage of aging. The APT results showed that adding Mn increased the number density of NiAl nanoparticles significantly, and Mn atoms partitioned into the NiAl nanoparticles, occupying the Al sites preferentially. The precipitation of NiAl nanoparticles was accelerated by the addition of Mn because Mn increased the nucleation driving force for NiAl precipitates and reduced the strain energy for the nucleation.

The depth profiling of the element content and precipitation phase distribution of the AA4045/AA3003mod (Al-1.5Mn-0.35Cu alloy)/AA4045 brazed sheets were investigated by optical microscope observation, electron probe microanalysis (EPMA), focused ion beam-scanning transmission electron microscopy (FIB-STEM). The electrochemical test and sea water acetic acid test (SWAAT) were performed to obtain the evolution of electrochemical responses and corrosion forms of brazed sheet. EPMA results showed that a diffusion layer with the thickness of approximately 50μm existed between the clad layer and core layer, where the Cu diffused from the core layer and Si diffused from the clad layer. It was found that brazing led to a significant low elements solid solution area at the end of the Si diffusion path, where the open circuit potential was lower by 25mV comparing to the unaffected region. Thus the diffusion zone can provide effective cathodic protection to the unaffected region as sacrificial anode by the potential gradient. The SWAAT analysis revealed the corrosion mechanism of the residual cladding was pitting and intergranular corrosion. This area with high density of intermetallic compounds and Si particles increased sensitivity to localized attacks. These results demonstrated the successful application of the FIB-STEM system in illustrating the electrochemical responses and corrosion propagation by an accurate in-depth characterization of intermetallic particles and the matrix solid solution.

The effects of Si addition to Fe on the formation and growth of intermetallic compounds (IMC) in Fe/Al composites were studied by Scanning electron microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and electron backscatter diffraction (EBSD) techniques. The results showed that: when annealing time was 1 h, the critical IMC formation temperature of Pure Al/Pure Fe, Pure Al/Fe+0.82Si, Al+0.88Si/Pure Fe and Al+0.88Si/Fe+0.82Si were 440 °C, 480 °C, 520 °C and 620 °C, respectively. The major IMC phase formed in the four composites after heat treatments at 640 °C/1h and 640 °C/24h was the η phase (Fe2Al5), and a large number of θ phase (Fe4Al13) particles were present in the η phase for the Pure Al/Pure Fe sample. When Si element was added to Fe and Al, Fe3Al2Si3phase and FeAl2Si phase were observed in the η phase. The thickness of the formed IMC layer in the four composites after heat treatment at 640 °C/1h was in the order: Pure Al/Pure Fe ≈ Pure Al/Fe+0.88Si > Al+0.888Si/Pure Fe ≈ Al+0.888Si/Fe+0.88Si. The growth activation energies of the IMC layer in the Pure Al/Pure Fe, Pure Al/Fe+0.82Si, Al+0.88Si/Pure Fe, Al+0.88Si/Fe+0.82Si samples were 76.1 kJ/mol, 276 kJ/mol, 349 kJ/mol and 519.6 kJ/mol, respectively. The effect of Si atoms on the formation of IMC was mainly by the interfacial enrichment mechanism and the new phase inhibition mechanism of FexAlySiz. The enrichment of Si at the interface of Al and Fe increased the growth activation energy and reduce the growth rate of IMC layer thickness. The formation of new FexAlySiz phase can inhibit the rapid growth of IMC phase along the C axis.

Abstract