Results 1 - 6 of 6
Results 1 - 6 of 6. Search took: 0.014 seconds
|Sort by: date | relevance|
[en] Highlights: • Hydroxyapatite (HA) powders were added to the electrolyte. • The HA powders have participated in the formation reactions of MAO coating. • The growth efficiency of MAO coating was greatly enhanced owing to the HA addition. • The specimen anodized in the HA-containing electrolyte has a better corrosion resistance. • The specimen anodized in the HA-containing electrolyte can more efficiently induce Ca–P precipitation. - Abstract: To improve the corrosion resistance of magnesium, micro-arc oxidation (MAO) coatings were prepared on magnesium substrates in an aqueous solution with and without hydroxyapatite (HA) powders addition. The micrographs of scanning electron microscopy (SEM), the energy dispersive spectrometer (EDS) spectra, and X-ray diffraction (XRD) analysis show that the HA powders added into the electrolyte have participated in the formation reactions of MAO coating and the growth efficiency of MAO coating is greatly enhanced. Potentiodynamic polarization tests and immersion tests in simulated body fluid (SBF) confirm that the specimen anodized in the HA-containing electrolyte has a better corrosion resistance than the specimen anodized in the HA-free electrolyte. Immersion tests also indicate that the specimen anodized in the HA-containing electrolyte can more efficiently induce Ca–P precipitation compared with the specimen anodized in the HA-free electrolyte
[en] This article mainly introduced the development and structure of canned motor pump and shaft seal pump at PWR. Especialy, the performance of canned motor pump for AP1000 and shaft seal pump was analyed and compared, their advantages and shortcomings were pointed out, which provided reference for the relevant nuclear power technical staff. (authors)
[en] Highlights: • Designed a high performance eutectic Al–Si die alloy by alloying Mg and La • All β-phases have changed to script-like π-phases by adding 3.6% Mg and 0.5% La. • Script-like π-phase changed to granular-like π-phase during solution treatment • The fragmentation mechanism of the script-like π-phase has been proposed. • Effects of Fe-rich intermetallics on the fracture behavior have been analyzed. In this paper, an efficient route that combined addition of excessive Mg (3.6 wt.%) and a trace of La (0.5 wt.%) as well as subsequent T6 heat treatment has been first proposed to modify the detrimental platelet-like β-Al5FeSi Fe-rich intermetallic to valuable granular-like π-Al8Mg3FeSi6 phase in eutectic Al–Si die alloys. The results of the DSC analysis revealed that majority of Mg play the leading role for precipitation of large script-like π-phase while rare earth La has the significant effect on modifying the eutectic Si phase simultaneously. A new phenomenon has been found that the morphology of the π-phase transformed from the script-like to fine granular-like by two main stages, including fragmentation and growth during solution treatment. By calculation, the coarsening rate coefficient of the segmented π-phase was about 2.9 × 10−19 m3/h during growth stage. The tensile testing measurements showed that the ultimate tensile strength (UTS), yield strength (YS), elongation to fracture (EI) and the quality index (Q) of T6 treated eutectic Al–Si die alloys alloying with 3.6 wt.% Mg and 0.5 wt.% La can reach 312 MPa, 270 MPa, 4.28% and 406 MPa respectively, and the enhanced mechanical properties corresponding to the evolution of the microstructure.
[en] Highlights: • Porous Zn scaffolds with different porosities were fabricated successfully. • The apparent density of porous Zn scaffolds is similar to that of natural bone. • The porous Zn scaffolds are suitable for non-load-bearing or low load-bearing applications. • The porous Zn scaffolds have a good corrosion resistance in SBF. • The porous Zn scaffolds can efficiently induce CaP precipitation. In the present work porous Zn scaffolds with different porosities were fabricated by air pressure infiltration method (APIM) as potential degradable materials for biomedical applications. The structures, mechanical properties, in vitro biodegradation of the porous Zn scaffolds were investigated. Scanning electron microscopy (SEM) observations show that the porous Zn scaffolds exhibit homogeneously distributed and interconnected pores. Compressive tests indicate that the compressive plateau stress of the porous Zn scaffolds decreases from 6.6 MPa to 2.8 MPa with increasing porosity from 54.2% to 71.0%. Correspondingly, the elastic modulus of the porous Zn scaffolds obtained by resonance method decreases from 2.65 GPa to 0.59 GPa. Compressive tests also confirm that localized collapse is the predominant compressive deformation mode under quasi-static compressive condition. Immersion tests suggest that the porous Zn scaffolds have a good corrosion resistance in simulated body fluid (SBF). In addition, the porous Zn scaffolds also have a good ability to induce CaP precipitation during immersion tests.
[en] Effect of precipitation during parent phase aging on the microstructure and properties of a CuAlMn shape memory alloy (SMA) refined by CuZr inoculant was investigated by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), Vickers hardness tester (VHT) and dynamic mechanical analyzer (DMA). It was found that after aging in parent phase at relatively low temperatures, such as 500 °C, the precipitation of α phase and γ2 phase in the CuAlMn SMA was uncontrollable because it was highly sensitive to aging time. While the aging in the temperature range of 530–620 °C could give rise to controllable precipitation, and by optimizing the microstructures in this way, the hardness and damping of the CuAlMn SMA could be significantly improved. Therefore, proper aging treatment is a convenient and feasible method to control the microstructure and properties of the Cu-based SMAs.
[en] Highlights: • Combined addition of Al-5Ti-1B ribbon and Zr element achieves a very efficient refining effect on ZA22 alloy. • The refining mechanisms of the grains of ZA22 alloy are discussed in detail. • With the decrease of grain size, the tensile strength, elongation and hardness of ZA22 alloy increase. • With the decrease of grain size, the damping of ZA22 alloy shows different variation patterns at different temperatures. A novel Al-5Ti-1B ribbon was prepared and used as inoculant to refine the grains of Zn-Al eutectoid (ZA22) alloy with the aim to significantly enhance the mechanical properties while remaining the high damping capacity. It was found that compared with the commercial Al-5Ti-1B rod the present ribbon had better refining effect on the ZA22 alloy due to its finer and more uniformly distributed TiB2 and L12-Al3Ti particles formed during rapid cooling process. It has been confirmed that both of the two kinds of particles could act as effective heterogeneous nucleation sites of α-Al phase, and then led to the refinement of α-Al grains. The combined addition of Al-5Ti-1B ribbon and Zr element could achieve the best refining effect because Zr could further promote the heterogeneous nucleation and hinder the growth of α-Al grains. Properties tests illustrated that with the decrease of average grain size, the tensile strength, elongation and hardness of the ZA22 alloy increased obviously because of the fine-grain strengthening and dispersion strengthening effects, while the damping showed different variation patterns within different temperature regions, which has been ascribed to the synthetic effect of two opposite influencing factors.