Effect of low-energy proton on the microstructure, martensitic transformation and mechanical properties of irradiated Ni-rich TiNi alloy thin films

Ni–48.5at%Ti thin films were irradiated in the austenite phase by different energy-level protons at a dose rate of 1.85×1012 p/(cm2·s),and the total dose was 2.0×1016 p/cm2.The microstructures of the thin films before and after irradiation were evaluated by transmission electron microscopy(TEM)and grazing-incidence X-ray diffraction(GIXRD),which showed that the volume fraction of Ti3Ni4 phase elevated with proton energy level.The influence of proton irradiation on the transformation behavior of the TiNi thin films was investigated by differential scanning calorimetry(DSC).Compared with the unirradiation film,the reverse transformation start temperatures(As)decreased by about 3°C after 120 keV proton-irradiation.The proton irradiation also had a significant effect on the mechanical properties of the TiNi thin films.After 120 keV energy proton-irradiation,the fracture strength increased by 8.44%,and the critical stress increased by 21.1%.In addition,the nanoindenter measurement image showed that the hardness of the thin films increased with the increase of proton-irradiation energy.This may be due to the defects caused by irradiation,which strengthen the matrix.

High-continuity genome assembly of the jellyfish Chrysaora quinquecirrha

DEAR EDITOR,The Atlantic sea nettle(Chrysaora quinquecirrha)has an important evolutionary position due to its high ecological value.However,due to limited sequencing technologies and complex jellyfish genomic sequences,the current C.quinquecirrha genome assembly is highly fragmented.Here,we used the most advanced high-throughput chromosome conformation capture(Hi-C)technology to obtain high-coverage sequencing data of the C.quinquecirrha genome.We then anchored these data to the previously published contig-level assembly to improve the genome.Finally,a high-continuity genome sequence of C.quinquecirrha was successfully assembled,which contained 1882 scaffolds with a N50 length of 3.83 Mb.The N50 length of the genome assembly was 5.23 times longer than the previously released one,and additional analysis revealed that it had a high degree of genomic continuity and accuracy.Acquisition of the high-continuity genome sequence of C.quinquecirrha not only provides a basis for the study of jellyfish evolution through comparative genomics but also provides an important resource for studies on jellyfish growth and development.

Effect of Sn Content on the Microstructural Features, Martensitic Transformation and Mechanical Properties in Ti-V-Al-Based Shape Memory Alloys

In the present study, it is expected to tailor the microstructural features, martensitic transformation temperatures and mechanical properties of Ti-V-Al shape memory alloys through adding Sn alloying elements, which further expands their applications. Sn addition results in the monotonous rising of average valence electron number (e/a). In proportion, the single α″ martensite phase directly evolves into merely β parent phase in present Ti-V-Al-based shape memory alloys, as Sn content increases from 0.5 to 5.0 at.%. Meanwhile, Sn addition causes the reduction in the grain size. Combined with transmission electron microscopy (TEM) observation and d electron theory analysis, it can be speculated that Sn addition can suppress the precipitation of ω phase. With increasing Sn content, fracture strength invariably decreases from 962 to 792 MPa, whereas the yield strength firstly decreases and then increases. The lowest yield stress for the stress-induced martensitic transformation of 220 MPa can be obtained in Ti-V-Al shape memory alloy by adding 3.0 at.% Sn. By optimizing 1.0 at.% Sn, the excellent ductility with a largest elongation of 42.1% can be gained in Ti-V-Al shape memory alloy, which is larger than that of the reported Ti-V-Al-based shape memory alloys. Besides, as a result of solution strengthening and grain refinement, Ti-V-Al-based shape memory alloy with 5.0 at.% Sn possesses the highest yield strength, further contributing to the excellent strain recovery characteristics with 4% fully recoverable strain.

Deposition and characterization for high-quality Ti-Ni-Cu thin films with higher Cu content

In order to attain high-quality Ti-Ni-Cu film,the surface morphologies,chemical compositions and mechanical properties of Ti-Ni-Cu thin films prepared by direct current(DC)magnetron sputtering at various processes were characterized by scanning electron microscopy(SEM),X-ray diffractometer(XRD)and tensile tests.The type of substrates,Ar pressure and sputtering power had significant effects on the quality and chemical composition of Ti-Ni-Cu thin film.Compared with Si and SiO_(2) slides,it was easier to obtain freestanding films by adopting glass or piezoid slide as substrates.The Ti-Ni-Cu thin film deposited at lower pressure(0.10 Pa)had a better density.The surface was featured with porous structure in the Ti-Ni-Cu thin film prepared by higher Ar pressure of 0.36 Pa.In addition,both the tensile strength and strain of annealed Ti-Ni-Cu thin film continuously increased with Ar pressure decreasing.Higher density contributed to the superior mechanical properties.The deposition rate firstly increased and then decreased with Ar pressure and sputtering power increasing.The composition of deposited Ti-Ni-Cu film can be tailored by changing sputter power.The deposited Ti-Ni-Cu thin films at different processing parameters were in amorphous state.In short,the present study offered the important theoretical basis for the preparation of Ti-Ni-Cu thin film with higher quality and performance.