Solidification Morphology Analysis of SLM of Cu Powder

The solidification morphology analysis of fine Cu powder melted by a raster scanned energy beam from a focused Nd:YAG laser is presented here. The powder was processed inside of sealed chamber where it was subjected to a high vacuum cycle. The laser fusion process consisted raster scanning a narrow rectangular pattern with a high density of scanning lines, the chamber was purged with inert gas during the process. Up to a 3.3 mm/s laser travel speed and maximum laser power level of 240 W were used to melt a 2 mm thick bed of loose powder. The resulting solidified ingots were separated into categories based on their shape integrity. Metallographic analysis by means of optical microscopy and scanning electron microscopy was performed on the cross section and longitudinal section of the ingots with homogeneous surface and complete shape integrity. Characterization revealed an elongated columnar grain structure with a grain orientation along the direction of the laser travel direction, some degree of porosity was observed too in some of the specimens. It was observed that grains diameter ranged from 10 to 100 µm and contained a two phase eutectic microstructure of copper and it oxides. Oxygen content was accounted from a 5.5 up to 8.1 atomic percent, a small percentage of chlorine was present, too. A 2 to 8 percent variation in the Vickers microhardness values were found between the different specimens when measured along the longitudinal section. These HV values corresponded to approximate 20-25% cold rolled oxygen free copper (80-90 HV). The ingots thus produced suggest that a multilayer structure from Cu powder could be build by the SLM process having sufficiently adequate compositional, microstructure and mechanical properties for functional applications.Mechanical Engineerin

Hyperon effects on the properties of β\beta-stable neutron star matter

We present results from Brueckner-Hartree-Fock calculations for $\beta$-stable neutron star matter with nucleonic and hyperonic degrees of freedom employing the most recent parametrizations of the baryon-baryon interaction of the Nijmegen group. Only $\Sigma^-$ and $\Lambda$ are present up to densities $\sim 7\rho_0$. The corresponding equations of state are then used to compute properties of neutron stars such as masses and radii.Comment: 4 pages, contributed talk at HYP2000, Torino, 23-27 Oct. 200

Kˉ∗\bar K^* meson in dense matter

We study the properties of $\bar K^*$ mesons in nuclear matter using a unitary approach in coupled channels within the framework of the local hidden gauge formalism and incorporating the $\bar K \pi$ decay channel in matter. The in-medium $\bar K^* N$ interaction accounts for Pauli blocking effects and incorporates the $\bar K^*$ self-energy in a self-consistent manner. We also obtain the $\bar K^*$ (off-shell) spectral function and analyze its behaviour at finite density and momentum. At normal nuclear matter density, the $\bar K^*$ meson feels a moderately attractive potential while the $\bar K^*$ width becomes five times larger than in free space. We estimate the transparency ratio of the $\gamma A \to K^+ K^{* -} A^\prime$ reaction, which we propose as a feasible scenario at present facilities to detect the changes of the properties of the $\bar K^*$ meson in the nuclear medium.Comment: 26 pages, 9 figures, one new section added, version published in Phys. ReV. C, http://link.aps.org/doi/10.1103/PhysRevC.82.04521

Charm at FAIR

Charmed mesons in hot and dense matter are studied within a self-consistent coupled-channel approach for the experimental conditions of density and temperature expected at the CBM experiment at FAIR/GSI. The $D$ meson spectral function broadens with increasing density with an extended tail towards lower energies due to $\Lambda_c(2593) N^{-1}$ and $\Sigma_c(2800) N^{-1}$ excitations. The in-medium $\bar D$ meson mass increases with density. We also discuss the consequences for the renormalized properties in nuclear matter of the charm scalar $D_{s0}(2317)$ and D(2400), and the predicted hidden charm X(3700) resonances at FAIR energies.Comment: 6 pages, 3 figures, to appear in the proceedings of ExcitedQCD 09, Zakopane, Poland, 8-14 February 200