Wen-yong Zhang

Mechanical properties of a two-phase alloy Mg–8%Li–1%Al processed by equal channel angular pressing

The microstructural evolution and room temperature tensile properties of Mg-8%Li-1%Al alloy processed by equal channel angular pressing (ECAP) at 403 K were investigated. It was found that the strength could be improved pass by pass. The elongation-to-failure decreased dramatically after the first ECAP pass, but could be improved pass by pass during the subsequent ECAP procedure. The microstructure analysis gave the explanations for these phenomena

Evolution of microstructures in materials induced by electropulsing.

Nanostructures were formed in several conventional materials under single electropulsing, that is nanophases of alpha-Cu(Zn) and beta-(CuZn) in a cold-worked alpha-Cu(Zn) alloy, nanosized gamma-Fe in a low-carbon steel, nanosized alpha-Al in a superduralumin, and orientated nanosized TiC in a TiC/NiCr cermet. The mechanisms responsible for the above nanostructured transitions can be attributed to the competition of many factors induced by electropulsing, including high-rate heating, thermal stress, reduced thermodynamic energy barrier and high-rate electron impacting. Also, many low-energy dislocation configurations, twins and stacking faults were formed in the copper alloy and cermet under the electropulsing. Such evolution of defects was associated with the electrical, thermal and stress energies induced by the electropulsing.

Effect of the substitution of Pr for Nd on microstructure and magnetic properties of nanocomposite Nd2Fe14B/α-Fe magnets

Microstructure and magnetic properties of melt-spun nanocomposite magnets with nominal compositions of (Nd1-xPrx)(9)Fe86B5 (x = 0-1) were investigated. Substitution of Nd by Pr could significantly improve the hard magnetic properties of the nanocomposite magnets; the intrinsic coercivity (H-i(c)) and the maximum magnetic energy product ((BH),,,) increase from 414kA/m and 124kJ/m(3) for x = 0 to 493 kA/m and 152 kJ/m(3) for x = 0.6, respectively. Further substituting Nd by Pr (x >0.6) strongly weakens exchange-coupling interaction between magnetically hard and soft phases

Effect of the substitution of Co for Fe on phase components and magnetic properties of melt-spun Pr9Fe85B5 nanocomposites

The phase evolution and magnetic properties of melt-spun Pr9Fe86-xCoxB5 (x=0,6,10,12,14,16) nanocomposites have been investigated. It was found that substitution of Co for Fe obviously raises the magnetization (M, H=6.5T), from 1.50 T for x=0 to 1.80 T for x=12. At the same time, the remanence (M-r), intrinsic coercivity (H-c) and maximum energy product (BHmax) changes from 0.96 T, 5.69 kOe, 11.8 MGOe for x=0 to 1.15T, 6.33 kOe, 17.3 MGOe for x=12, respectively. Further substitution of Co for Fe results in a decrease of M-r and BHmax because of the presence of minor amounts of 1:5 and 2:17 phases. Thermomagnetic analysis shows that the Co atoms enter into both the magnetically hard and soft phases. The Curie temperature of the hard magnetic phase increases linearly by increasing Go-substitution at the rate of DeltaT(c)=9 degreesC/at% Pr

Melt-spun magnetically anisotropic SmCo5 ribbons with high permanent performance

We have succeeded in preparing magnetically anisotropic SmCo5 ribbons with high permanent performance by single-roller melt spinning at low wheel velocity. The anisotropy is associated with a crystallographic texture formed during melt-spinning process, with the c-axis parallel to the longitudinal direction of the ribbons. The formation of the crystallographic texture is attributed to a directional solidification process resulting from a thermal gradient. A remanence of 9.1 kG, remanence ratio of 0.9, intrinsic coercivity of 16.2 kOe and energy product of 18.2 MGOe at room temperature are obtained in the melt-spun and subsequently annealed SmCo5 ribbons prepared at 5 m/s

Formation of nanophases in a Cu–Zn alloy under high current density electropulsing

The microstructure of samples before and after a high current density electropulsing treatment was characterized by using high-resolution transmission electron microscopy. It has been found that in the coarse-grained Cu-Zn alloy subjected to the electropulsing treatment, two nanophases were formed, alpha-Cu(Zn) and beta-(CuZn), the average grain size of which is about II nm. A possible mechanism for the formation of nanophases was proposed. The experimental results indicated that electropulsing, as an instantaneous high-energy input, plays an important role in the nonequilibrium microstructural changes in materials and serves as a potential processing approach to synthesize nanostructured materials.

Magnetic properties of Sm- and Cu-doped oriented SmCo5 ribbons prepared by melt spinning

Oriented melt-spun ribbons with composition Sm1+Y(Co1−XCux)5 (X=0–0.3 and Y=0–0.2) were fabricated with a wheel speed of 5 m/s, followed by annealing in the temperature range of 600–1000u200a°C for 30 min. Our results show that a high degree of texture, in which the c axis is parallel to the longitudinal direction of the ribbons, is obtained in all above ribbons. The room temperature intrinsic coercivity can be significantly enhanced by both Sm additions and Cu substitution and coercivities of 21 and 12.4 kOe an achieved in Sm1.15Co5 and Sm(Co0.8Cu0.2)5 ribbons, respectively. Compared with the Sm-doped ribbons, Cu-doped ribbons exhibit a better thermal stability of coercivity and a high intrinsic coercivity of 5.2 kOe can be maintained at 300u200a°C in Sm(Co0.8Cu0.2)5 ribbons. Further analysis indicates that the coercivities of Sm- and Cu-doped ribbons are determined by different demagnetization mechanisms.

Ultrafine WC-10Co cemented carbides fabricated by electric-discharge compaction

This research investigates the microstructure and mechanical properties of ultrafine WC-10Co cemented carbides fabricated by an electric-discharge compaction (EDC) process, from powder synthesized by a spray-conversion process (SCP). Due to a short holding time during EDC, a grain size as small as 120 nm can be achieved. We also found that dispersion of pores in WC-Co cemented carbides may contribute to fracture toughness, besides the bridging ligament mechanism.

Formation of nanoscale alpha-Al in a superdralumin under high current density electropulsing

Chinese Acad Sci, Shenyang Natl Lab Mat Sci, Inst Met Res, Shenyang 110016, Peoples R China.;Zhang, W (reprint author), Chinese Acad Sci, Shenyang Natl Lab Mat Sci, Inst Met Res, 72 Wenhua Rd, Shenyang 110016, Peoples R China

The hard magnetic properties of nanocomposite Nd3.6Pr5.4Fe83Co3B5 ribbons prepared by melt spinning

Abstract Nanocomposite Nd 3.6 Pr 5.4 Fe 83 Co 3 B 5 ribbons were prepared by direct melt spinning at different wheel speeds. The hysteresis loop of the ribbons prepared at wheel speed V=20 m/s shows a single hard magnetic behavior with high coercivity. The values of remanence M r =11.3 kG s , intrinsic coercivity i H c =6.0 kOe and energy product ( BH ) max =17.2 MG Oe are obtained at room temperature. Transmission electron microscopy and magnetic force microscopy have been employed to image the microstructure and magnetic domains in the ribbons. Due to the unnegligible inter-grain exchange coupling, interaction domains are observed. The shape of the demagnetization curve in the second quadrant at different temperature gives more information about inter-grain exchange coupling. The coercivity mechanism is discussed.