Nanomechanical properties of Mg–Al intermetallic compounds produced by packed powder diffusion coating (PPDC) on the surface of AZ91E

A packed powder diffusion coating (PPDC) treatment produced two intermetallic layers on the surface of the commercial magnesium alloy AZ91E. The beta-phase (Mg17Al12) was immediately on top of the AZ91E, on top of which was the tau-phase (Mg-32(Al,Zn)(49)). Nanoindentation showed that the elastic modulus and hardness of each of the intermetallic compounds was significantly greater than that of the AZ91E substrate. Staircase displacement bursts occurred during nanoindentation of the intermetallic compounds, attributed to the combination of incipient plasticity at low loads, and the development of dislocation networks due to dislocation pile ups around the indentation at higher loads. Crystallographic analysis of beta phase orientations using EBSD showed that the nanomechanical properties of the intermetallic compound produced through PPDC treatment were isotropic. (C) 2013 Elsevier B.V. All rights reserved

LASER SPECTROSCOPY OF NiBr: ROTATIONAL ANALYSIS OF THE 2Π3/2−X2Π3/2^{2}\Pi_{3/2} - X^{2}\Pi_{3/2} TRANSITION

Author Institution: Department of Chemistry, The University of Hong Kong; Department of Chemistry, The University of Hong KongNiBr was produced in a supersonic free jet expansion in argon by the reaction of laser ablated nickel atom and bromoethane $(C_{2}H_{5}Br)$ vapour. High resolution laser induced fluorescence spectra between 724 and 810 nm have been obtained using a c.w. single frequency Ti:sapphire laser. 8 bands have been recorded and 3 were assigned to the $^{2}\Pi_{3/2}- X^{2}\Pi_{3/2}$ transition. Transition lines from four isotopic molecules: $^{58}Ni^{79}Br$, $^{58}Ni^{81}Br$, $^{60}Ni^{79}Br$ and $^{60}Ni^{81}Br$, are observed and analysed. Least squares fit of measured lines of each isotopic molecule was performed. Molecular constants of all four isotopic molecules will be reported. Acknowledgement: This work was carried out with support from the Hong Kong Research Grants Council