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The RANS (RIKEN Accelerator driven Neutron Source), one of compact accelerator neutron sources (CANS), tries to expand its performance by installing a cold neutron which may provide new opportunities in many applications. RANS is a low power CANS with a proton beam of 7 MeV and 100 µA at maximum. A moderator system was constructed based on results of optimization design study with mesitylene. Recently, we have done performance tests aiming at showing characteristics as cold neutron source. Cryogenic mesitylene moderator was installed on a plug with a new target moderator reflector configuration of RANS. Experiment using a gas electron multiplier (GEM) detector was carried out to measure neutron spectra of the cold moderator. This paper describes performance of the cold moderator in terms of 1) Cold neutron gain of optimization design with respect to a polyethylene moderator, 2) Temperature dependency of cold neutron spectrum flux regarding scattering kernel (SK), and 3) comparison between experiment and calculation. A note is given for comparison between calculations with different SKs available. Also, two-dimensional imaging of cold and thermal neutron spectrum flux on the viewed surface is shown with a pinhole slit configuration.

A sample-motion-synchronized neutron stroboscope is developed using the RIKEN accelerator-based compact neutron source (RANS). When a sample reaches a specified rotation phase, a phase timing signal is generated, triggering a proton pulse at the proton accelerator. A neutron pulse exposes the imaging detector through the sample. By controlling the delay time between the phase signal and the proton pulse timing, the neutron exposure timing is always synchronized with the specific sample rotation phase. A sample rotating at a speed of 1800 RPM is prepared, and clear still images of neutrons are taken.

The Optimized Energy Degrading Optics (OEDO) beamline was constructed at RIBF to produce slowed-down, well-focused radioactive-isotope beams at 10–50 MeV/u, and began operation in June 2017. We examined the performance of the OEDO system by decelerating high-energy medium-mass radioactive ions. The main components of the OEDO beamline are two superconducting quadrupole triplet magnets and one radio-frequency deflector. This paper introduces the unique design of the ion optics of the beamline and describes the achieved performance of the beamline in the commissioning and following physics experiments. We will discuss the properties of energy-degraded beams produced by the OEDO beamline by comparison of simulations and the achieved performance.

Background: Mg 24 is a strongly deformed nucleus in the ground state. Deformation effects can be observed in the structure of the isoscalar giant monopole and quadrupole resonances. Mg 24 is also a nucleus that is well known to present different types of cluster-oscillation modes. Both giant resonances and cluster states are strongly populated by isoscalar transitions. Purpose: To extract the E 0 , E 1 , and E 2 transition strengths via Li 6 scattering. The Li 6 probe is a powerful tool for investigating the isoscalar nuclear response with a very favorable ratio of resonance-to-continuum background. Method: Double-differential cross sections of Li 6 inelastic scattering, at the beam energy of 100 MeV/u, were measured in the excitation-energy range 10 – 40 MeV and scattering angles 0 − 3 ∘ . A multipole-decomposition analysis was performed for extracting the isoscalar E 0 , E 1 , and E 2 strength distributions. Results: The extracted multipole strengths were compared with predictions from consistent quasiparticle random phase approximation calculations. The theoretical predictions are in fair agreement with the experimental data. The E 0 strength was also compared with results from antisymmetrized molecular dynamics calculations found in the literature. A few peaks in the experimental data might be associated with clustering in Mg 24 . Conclusions: Ground-state deformation effects were observed in the isoscalar giant monopole resonance (ISGMR) and isoscalar giant quadrupole resonance (ISGQR) distributions. The ISGMR strength is split in two peaks around 19 and 28 MeV. The ISGQR exhibits a pronounced peak at 20 MeV with a broadening at the low-energy region, similar to predictions from microscopic calculations. Signatures of excitation of cluster states were observed in the E 0 response. Further studies including particle-decay measurements will be required to confirm the nature of the observed peaks.

Cu-Pd-Ag alloy is widely used in electronic device applications due to its relatively low electric resistance. To obtain higher strength wire, age-hardening is usually conducted to this alloy wire. However, the detailed hardening mechanism of Cu-Pd-Ag alloy was not clarified enough. In the present paper, we investigated the microstructure and hardness of the Cu-Pd-Ag alloy wire with aging treatment. Original alloy contained many rods with an Ag-rich α phase extended along the wire direction in a Cu-rich α phase matrix. After heat treatment of 623K with 1 hour, the matrix was transformed to the β phase contained many elongated α2 phases as nanolamellar structure. Many β’ phase precipitated in the rods. Hardness measured with nanoindentation test showed that the matrix had a higher value than that of the rods. In the Cu-Pd-Ag alloy wire, the nanolamellar structure of the matrix was revealed to contribute to the hardening of the wire.

Inelastic ${}^{6}$Li scattering at 100 MeV/u on ${}^{12}$C and ${}^{93}$Nb have been measured with the high-resolution magnetic spectrometer Grand Raiden. The magnetic-rigidity settings of the spectrometer covered excitation energies from 10 to 40 MeV and scattering angles in the range $0^\circ < \theta_{\text{lab.}}< 2^\circ$. The isoscalar giant monopole resonance was selectively excited in the present data. Measurements free of instrumental background and the very favorable resonance-to-continuum ratio of ${}^{6}$Li scattering allowed for precise determination of the $E0$ strengths in ${}^{12}$C and ${}^{93}$Nb. It was found that the monopole strength in ${}^{12}$C exhausts $52 \pm 3^\text{(stat.)} \pm 8 ^\text{(sys.)}$\% of the energy-weighted sum rule (EWSR), which is considerably higher than results from previous $\alpha$-scattering experiments. The monopole strength in ${}^{93}$Nb exhausts $92 \pm 4^\text{(stat.)} \pm 10 ^\text{(sys.)}$\% of the EWSR, and it is consistent with measurements of nuclei with mass number of $A\approx90$. Such comparison indicates that the isoscalar giant monopole resonance distributions in these nuclei are very similar, and no influence due to nuclear structure was observed.

Cu-Pd-Ag alloy wires with a relatively low Ag content are used widely in electronics. This alloy is usually subjected to age hardening to increase its strength. However, the alloy microstructure that results when the alloy is processed as a wire has not been clarified sufficiently to elucidate the hardening mechanism. A clarification of the microstructure is critical to control the mechanical properties of the alloy wire. In this study, we investigated the detailed microstructure variation of the alloy wire after heat treatment. Microscopy showed that the alloy wire contained many parallel rods with an Ag-rich α phase that extended along the axial direction of a Cu-rich α-phase matrix before heat treatment. After heat treatment at 623 K for 1 hour, the morphology of the rods in the matrix remained mostly unchanged. Detailed observations revealed that the matrix was transformed to a nanolamellar structure with β and α2 phases. Many β′ phases with a thickness of a few atomic layers precipitated in the rods. Both nanostructures investigated in this study were expected to contribute to wire hardening through a short-fiber strengthening mechanism.

In this study, new butt welding technique was proposed to join polymeric materials in which the polymeric material is softened by a heated tool due to the Joule effect heating of the electric curre...

The effect of Cu coating metallic interlayer on the weldability, joint strength, and interfacial microstructure during high-power ultrasonic spot welding (HP-USW) of AZ31B Mg alloy has been studied. Interlayered samples exhibited good weldability and they resulted in strong sound joints with nearly the same strength as joints without interlayer, with the distinction of lower energy being required. The Cu interlayer affected the thermal and vibrational properties of the interface, as the maximum interface temperature decreased and approached better uniformity across the weld nugget. The base metal grain structure changed to equiaxed larger grains after ultrasonic welding and a chain of parent metal small grains were observed around the interface. A binary intermetallic compound product of Mg-Cu, which was rich in Mg, has been found around the interface that was diffused toward base metal. According to the electron probe micro-analyzer (EPMA) results, alongside temperature measurements and hardness data, the formation of Mg2Cu is suggested in this region. At the interface centerline, a narrow region was identified that was composed of Mg, Cu, and Al. Complementary transmission electron microscopy analysis estimated that Al-containing reaction product is a ternary alloy of the MgCuxAly type. The dispersion of fine grain intermetallic compounds as discrete particles inside Mg substrate in both interfacial regions formed a composite like structure that could participate in joint strengthening.

The OEDO (Optimized Energy Degrading Optics for RI beam) beamline has been developed to obtain low-energy (10 – 50 MeV/u) RI beams by slowing down the secondary beams at RIBF, RIKEN. Such beams are useful probes to investigate nuclear structure by means of nucleon transfer and Coulomb excitation reactions. The beamline is designed to produce a well-focused beam of small energy spread with the help of the angle-tuneable wedge degrader and the radio-frequency deflector. The commissioning and first physics experiments using the OEDO beamline were carried out in 2017. OEDO successfully provided the energy-degraded beams of Se, Zr, and Pd. Its performance including the optics and transmission was evaluated using those experimental data and it functions properly as designed. We expect that our novel beamline shed a light on the experimental approaches involving nuclear reactions at several tens of MeV/u to expand our knowledge of nuclei far beyond the line of stability.

Our study evaluated the microstructure formation mechanism and weldability of Mg–Zn–Y alloy with a long-period stacking ordered (LPSO) structure phase and applied ultrasonic spot welding technology to the welding for the first time. The microstructure evolution of the joints depended on the macro shape of the welding tip with both flat and slope region. A band with fine grains was generated around the weld interface. In the slope region, a novel waved band was generated, and it was revealed that the plastic flow occurred in the entire band. Outside the band in the flat region, Zn and Y segregated at the grain boundaries of an Mg-matrix. The presence of temperature distribution along the weld interface was suggested from the segregation region. Furthermore, the maximum weld strength was obtained with the weld condition in which the novel band was generated, and it was revealed that the enhancement of the plastic flow in the slope region contributed to an increase in the weld strength. The fracture modes transmuted with the condition and the base metal plug fracture mode was exhibited.

Background: Inelastic neutrino-nucleus scattering is important for understanding core-collapse supernovae and the detection of emitted neutrinos from such events in earth-based detectors. Direct measurement of the cross sections is difficult and has only been performed on a few nuclei. It is, therefore, important to develop indirect techniques from which the inelastic neutrino-nucleus scattering cross sections can be determined. Purpose: This paper presents a development of the (Li-6,Li-6*[T = 1, T-z = 0, 0(+), 3.56 MeV]) reaction at 100 MeV/u as a probe for isolating the isovector spin-transfer response in the inelastic channel (Delta S = 1, Delta T = 1, Delta T-z = 0) from which the Gamow-Teller transition strengths from nuclei of relevance for inelastic neutrino-nucleus scattering cross sections can be extracted. Method: By measuring the Li-6 ejectile in a magnetic spectrometer and selecting events in which the 3.56 MeV gamma ray from the decay of the Li-6*[3.56 MeV] state is detected, the isovector spin-transfer selectivity is obtained. High-purity germanium clover detectors served to detect the gamma rays. Doppler reconstruction was used to determine the gamma energy in the rest frame of Li-6. From the Li-6 and 3.56 MeV gamma-momentum vectors the excitation energy of the residual nucleus was determined. Results: In the study of the C-12(Li-6,Li-6*[3.56 MeV]) reaction, the isovector spin-transfer excitation-energy spectrum in the inelastic channel was successfully measured. The strong Gamow-Teller state in C-12 at 15.1 MeV was observed. Comparisons with the analog C-12(Li-6,He-6) reaction validate the method of extracting the Gamow-Teller strength. In measurements of the Mg-24, Nb-93(Li-6,Li-6*[3.56 MeV]) reactions, the 3.56 MeV gamma peak could not be isolated from the strong background in the gamma spectrum from the decay of the isoscalar excitations. It is argued that by using a gamma-ray tracking array instead of a clover array, it is feasible to extend the mass range over which the (Li-6,Li-6*) reaction can be used for extracting the isovector spin-transfer response up to mass numbers of similar to 25 and perhaps higher. Conclusions: It is demonstrated that the (Li-6,Li-6*[3.56 MeV]) reaction probe can be used to isolate the inelastic isovector spin-transfer response in nuclei. Application to nuclei with mass numbers of about 25 or more, however, will require a more efficient gamma-ray array with a better tracking capability.

We systematically measured the differential cross sections of inelastic $\ensuremath{\alpha}$ scattering off self-conjugate $A=4n$ nuclei at two incident energies ${E}_{\ensuremath{\alpha}}=130\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}$ and $386\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}$ at Research Center for Nuclear Physics, Osaka University. The measured cross sections were analyzed by the distorted-wave Born-approximation (DWBA) calculation using the single-folding potentials, which are obtained by folding macroscopic transition densities with the phenomenological $\ensuremath{\alpha}N$ interaction. The DWBA calculation with the density-dependent $\ensuremath{\alpha}N$ interaction systematically overestimates the cross sections for the $\mathrm{\ensuremath{\Delta}}L=0$ transitions. However, the DWBA calculation using the density-independent $\ensuremath{\alpha}N$ interaction reasonably well describes all the transitions with $\mathrm{\ensuremath{\Delta}}L=0$--4. We examined uncertainties in the present DWBA calculation stemming from the macroscopic transition densities, distorting potentials, phenomenological $\ensuremath{\alpha}N$ interaction, and coupled channel effects in $^{12}\mathrm{C}$. It was found that the DWBA calculation is not sensitive to details of the transition densities nor the distorting potentials, and the phenomenological density-independent $\ensuremath{\alpha}N$ interaction gives reasonable results. The coupled-channel effects are negligibly small for the ${2}_{1}^{+}$ and ${3}_{1}^{\ensuremath{-}}$ states in $^{12}\mathrm{C}$, but not for the ${0}_{2}^{+}$ state. However, the DWBA calculation using the density-independent interaction at ${E}_{\ensuremath{\alpha}}=386\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}$ is still reasonable even for the ${0}_{2}^{+}$ state. We concluded that the macroscopic DWBA calculations using the density-independent interaction are reliably applicable to the analysis of inelastic $\ensuremath{\alpha}$ scattering at ${E}_{\ensuremath{\alpha}}\ensuremath{\sim}100\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}/\mathrm{u}$.

In this work, spherical Sn and SnO2 nanoparticles smaller than 5 and 20 nm, respectively, were synthesized using pulsed plasma in deionized water, simply and environmentally friendly. The tetragonal Sn nanoparticles showed good crystallinity and slight increase in lattice parameters. Thermo-gravimetric analysis revealed insignificant weight loss from the particles, indicating their thermal stability up to 500 °C. The Sn nanoparticles then were annealed at 800 °C; in result, cassiterite phase of SnO2 nanoparticles were successfully obtained. Structural and morphological analysis indicated the full oxidation of Sn and size growth of SnO2 nanoparticles upto 20–25 nm. The SnO2 nanoparticles showed good photocatalytic activity in degradation of organic dyes, such as methylene blue and methyl orange.

The aim of the present study was to examine the effect of the somatic cell count (SCC) in milk on reproductive performance, such as pregnancy status in the prepartum period and ovarian function in the postpartum period, in dairy cows. Blood samples were collected every week from one month prepartum to parturition in order to measure the concentrations of 13,14-dihydro-15-keto-PGF2α (PGFM), estrone sulfate (E1S) and progesterone. Milk samples were collected three times per week in both the prepartum (for one month before the dry period) and postpartum periods (for 3 months immediately after parturition) to measure the SCC. Progesterone was also determined in the whole milk of postpartum cows to define the day of the first ovulation. In the prepartum period, the maximum SCC negatively correlated with the pregnancy period (r = –0.77), but not the calf birth weight. Positive and negative correlations were observed between the average SCC and PGFM or progesterone concentrations in plasma, respectively (r = 0.84 or –0.92, respectively), at 39 weeks of pregnancy. In the postpartum period, a correlation was observed between the day of the first ovulation and both the average and maximum SCC (r = –0.74 and –0.75, respectively), whereas days open was not related to the SCC. These results suggest that a high SCC in the prepartum period may advance parturition by increasing PGF2α and decreasing progesterone and that the first ovulation in the postpartum period was affected by a high SCC.

Pure orthorhombic-phase WO3·H2O nanoparticles with sizes of about 5 nm were synthesized by pulsed plasma in deionized water, in which tungsten electrodes provide the source of tungsten and the water is the source of oxygen and hydrogen. The quenching effect and liquid environment inherent in this pulsed plasma in liquid method resulted in ultra-small particles with lattice lengths (a = 5.2516 A, b = 10.4345 A, c = 5.1380 A) larger than those of reference lattices. The emission lines of W I atoms, W II ions and H I atoms were observed by an optical emission spectrum in order to gather information on the synthetic mechanism. These nanoparticles showed higher absorption in the visible region than did ST-01 TiO2 and Wako WO3 nanoparticles. The WO3·H2O nanoparticles displayed more activity in the photocatalytic test than did the commercial TiO2 sample (ST-01). Also, the absorption edge of WO3·H2O shifted to longer wavelengths in the UV-Vis absorption pattern relative to that of the anhydrous tungsten oxide.

An Al/glass joint created by using ultrasonic welding was analyzed by means of multiscale observation techniques. A cross-sectional analysis of the microstructure revealed that a directly joined interface without reaction phases formed at the periphery of a round joined region. The size of Al grains markedly decreased after ultrasonic welding and some subgrains were observed along the interface. The finer Al grains observed around the periphery of the joined interface showed active plastic flow that promoted welding.

Liquid and supercritical carbon dioxide (LCO2, SCCO2) have been used as a porogen to swell self-organized nano-structure of an amphiphilic side-chain type liquid crystalline PEO–b-PMA(Az) copolymer. Carbon dioxide interacts with the hydrophilic PEO domain rather than the PMA matrix. The preferential interactions of PEO component with carbon dioxide result in a solvent-induced surface topology changes and the generation of a nano-porous template. The area density of the nano-pores is identical to that of the original copolymer film while keeping the hexagonally packed PEO nano-scale organization. Since the process is based on the gases diffusion on solid surfaces under controlled temperature and since neither polymer block is fundamentally altered by the sorption effect, the process is fully reversible. The supercritical condition of CO2 treatment gives rise to the highest expansion of pre-patterned PEO cylinders and consecutively induces the retardation of PEO crystallization. This versatile thermo-diffuso approach would be applied to a wide variety of pre-patterned copolymers systems for nano-templating applications requiring nano-scale features sizes and/or area feature densities.

High temperature phase tungsten carbide and titanium carbide coated with graphitic carbon (WC1−x@C and TiC@C) nanoparticles were synthesized by pulsed plasma in liquid. HRTEM results show that the average size of WC1−x@C and TiC@C nanoparticles are 30 and 35 nm, respectively. Raman spectroscopy revealed well-organized graphitic coatings, which make the nanoparticles stable at higher temperatures and resistant to oxidation. Refinement of the XRD profiles showed larger cell parameters compared to JCPDS cards. Furthermore, thermogravimetric analyses showed the higher thermal stability up to 601 and 543.4 °C, for the WC1−x@C and TiC@C nanoparticles, these are 43% and 36% more compared to the thermal stability of previously reported nanoparticles, which degraded at around 350 °C.

The purpose of this study was to design cyclodextrin (CyD)-based pseudorotaxane-like supramolecular complexes with various isoprenoid compounds, such as reduced coenzyme Q10 (R-CoQ10), squalene, tocotrienol, and teprenone, and to evaluate their pharmaceutical properties. Squalene, tocotrienol, and teprenone formed precipitates with β-CyD and γ-CyD in aqueous solution, whereas R-CoQ10 formed precipitates with γ-CyD aqueous solution. The results of powder X-ray diffraction and (1)H-NMR analyses indicated that these precipitates are derived from pseudorotaxane-like supramolecular complexes. The photostability of teprenone was markedly improved by complexation with CyDs, especially in the γ-CyD system. In addition, the dispersion rates of teprenone in the γ-CyD system were higher than those in the β-CyD system, compared with the corresponding physical mixtures. In conclusion, pharmaceutical properties such as photostability and dispersion rates of isoprenoid compounds were improved by the formation of pseudorotaxane-like supramolecular complexes with β-CyD and/or γ-CyD.

This report describes a two-dimensional monitoring system for milling machines using small-diameter tools. Small-diameter tools are used for high-speed milling, and they are indispensable for high-quality and high-productivity manufacturing. However, tool breakage occasionally occurs, and this becomes a serious problem in automated production. This study aims to develop a system for monitoring the cutting state that can prevent tool breakage. The proposed system consists of two charge-coupled device (CCD) cameras, an image processing device, a man-machine controller (MMC), and a machining center with an open computer numeric (CNC). This monitoring system is connected to the machining center by Ethernet. It enables the precise measurement of tool deflection during high-speed milling. In an experiment, we applied this system to the end milling of a steel plate under different cutting conditions, and we examined the relationship between tool deflection and the cutting conditions. In addition, we applied this monitoring system to measure tool wear, and we examined the relationship between tool deflection and tool wear. It was found that the proposed system enabled in-process monitoring of the cutting state and tool wear.

We synthesized onion-like carbon-encapsulated Co, Ni, and Fe (Co-C, Ni-C, and Fe-C) magnetic nanoparticles with low cytotoxicity using pulsed plasma in a liquid. The pulsed plasma is induced by a low-voltage spark discharge submerged in a dielectric liquid. The face-centered cubic Co and Ni, and body-centered cubic Fe core nanoparticles showed good crystalline structures with an average size between 20 and 30 nm were encapsulated in onion-like carbon coatings with a thickness of 2-10 nm. Vibrating-sample magnetometer measurements revealed the ferromagnetic properties of as-synthesized samples at room temperature (Co-C=360 Oe, Fe-C=380 Oe, and Ni-C=211 Oe). Raman-spectroscopy analysis found onion-like carbon shells composed of well-organized graphitic structures. Thermal gravimetric analysis showed a high ___________________*Corresponding author. Tel/Fax: +08052593295. E-mail address: mashimo@gpo.kumamoto-u.ac.jp (T. Mashimo)stability of the as-synthesized samples under thermal treatment and oxidation. Cytotoxicity measurements showed higher cancer cell viability than samples synthesized by different methods.

Mg96Zn2Y2 is widely studied due to its high tensile yield strength and elongation. These excellent properties were considered to relate to the nanostructure of the alloy such as fine-grained α-Mg matrix and bent long period stacking ordered (LPSO) structure. In order to extend the application of this Mg alloy, development of the welding technique is indispensable. In the light of the reliability and productivity, resistance spot welding is an attractive method to join this Mg alloy. In this study, we joined the Mg alloys by the resistance spot welding with cover plates. Mechanical properties and structures of the nugget of the joints were investigated. In the case of the joints welded with cover plates, the welded region of the Mg alloy sheets were covered with steel plates to supply adequate heat for welding. Joints of extruded Mg96Zn2Y2 were obtained at relatively low welding current. The tensile strength of Mg96Zn2Y2 alloy was higher than that of the commercial Mg alloy AZ31B joints. Mg96Zn2Y2 base alloy had extended LPSO phase along extruded direction in α-Mg grains. At the nugget, net-like secondary phase was produced in the Mg grains. The relationship between the microstructure in the joints and mechanical properties were discussed.

We have proposed a surface planarization method for silicon carbide (SiC) substrates using Fe abrasive particles and hydrogen peroxide (H2O2) solution. In this proposed method, the SiC surface is first oxidized by hydroxyl radicals generated by the decomposition of H2O2 on the surface of Fe abrasive particles, and then an oxide layer is formed on the SiC substrate. This layer is then mechanically and/or chemically removed by Fe abrasive particles and H2O2 solution, resulting in a smooth and damage-free SiC surface. In this study, the chemical mechanical planarization of a 4H-SiC ( 0 0 0 1 ¯ ) C-face substrate by our proposed method was examined. The morphology was observed by phase-shift interferometric microscopy, Nomarski differential interference contrast microscopy and atomic force microscopy. The subsurface damage on the processed surface was evaluated by high-resolution transmission electron microscopy. These observations showed that the surface roughness of the SiC substrate was markedly improved and that a damage-free and scratch-free SiC surface was obtained. These results provide useful information for preparing high-integrity SiC substrates with high efficiency.

Recently, Mg96Zn2Y2 alloy was widely studied due to its excellent mechanical properties. These properties were considered to relate to the nanostructure of the alloy such as α-Mg matrix and bent long period stacking ordered (LPSO) structure. In this study, as the first step to the mechanical property control, we applied various spot welding methods to the Mg alloy to control the structure of the joints. The specimen used was an extruded Mg96Zn2Y2 alloy. The sheets were cut from this alloy rod for resistance spot welding. Three kinds of spot welding methods were applied to join the Mg alloy, such as spot welding with cover plates, long-time spot welding, and water-cooled spot welding. In the base metal, secondary phases extended along extruded direction at approximately 30μm intervals were produced in the α-Mg matrix. The secondary phase contained 14H-type LPSO structure. In the nugget of the joint welded with cover plates, a secondary phase was produced like a net in the α-Mg grain which was approximately 30μm in diameter. Both 14H-type and 18R-type LPSO were observed in the secondary phase. In the nugget produced by the long-time spot welding, a secondary phase tended to segregate to the grain boundary of the α-Mg grains. The structure of LPSO was 18R-type. In the water-cooled welding, strong directionality of the secondary phase texture was observed around the edge of the nugget. These results showed that the nugget nanostructure of Mg96Zn2Y2 dramatically varied depending on the above adopted methods of spot welding.