Zn-Neighbor Cu NQR in Zn-Substituted YBa2Cu3O7-d and YBa2Cu4O8

We studied local electronic states near Zn in optimally doped YBa$_2$(Cu$_{1-x}$Zn_x)$_3$O$_{7-\delta}$ and underdoped YBa$_2$(Cu$_{1-x}$Zn_x)$_4$O$_8$ via satellite signals of plane-site Cu(2) nuclear quadrupole resonance (NQR) spectra. From the relative intensity of Cu NQR spectra, the satellite signals are assigned to Zn-neighbor Cu NQR lines. The Cu nuclear spin-lattice relaxation time of the satellite signal is shorter than that of the main signal, which indicates that the magnetic correlation is locally enhanced near Zn both for the underdoped and the optimally doped systems. The pure YBa$_2$Cu$_4$O$_8$ is a stoichiometric, homogenous, underdoped electronic system; nevertheless, the Zn-induced inhomogeneous magnetic response in the CuO$_2$ plane is more marked than that of the optimally doped YBa$_2$Cu$_3$O$_{7-\delta}$.Comment: 9 pages including 8 figures, to be published in Phys. Rev.

Impacts of warm equal-channel angular pressing on microstructure and mechanical properties of granular pearlitic steel

Abstract Equal-channel angular pressing (ECAP) of granular pearlite high-carbon steel at 650 °C via the Bc route is thoroughly investigated. Together with microstructural evolution investigated through scanning and transmission electron microscopies, microtensile and microhardness testing are conducted for their mechanical properties. After four passes of warm deformation, the formed ultra-microduplex structure is found to contain both ferrite grains of size ≈0.45 μm and cementite particles with the diameter of ≈0.3 μm. The corresponding microhardness and tensile strength are observed to increase first, followed by a decrement with the number of deformations passes. Meanwhile, yield strength and yield ratio increase with the ECAP passes, along with a slight decrease in elongation. The fracture morphology also changes from many deep dimples before ECAP to many small dimples after ECAP application, denoting a typical ductile fracture of the pearlitic steel