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The role of alloying elements in the improvement of the high temperature strength of Al-12Si(CuNiMg) cast alloys used for automotive piston applications was investigated. The addition of alloying elements such as Mn, Cr, Ti and Ge was studied and the detailed characterization of the composition and morphology of the constituent phases after over aging at 350 for 1000 hrs was performed. The compositions and volume fractions of the equilibrium phases determined by thermodynamic calculation were compared with the experimental results. The addition of transition elements, including Mn, Cr and Ti, increased the volume fraction of the intermetallic phases, which effectively enhanced the high temperature strength of the alloys. Among these transition elements, Mn turned out to be the most effective alloying element. After adding up to 0.5wt% of Mn, a large number of intermetallic phases, α-Al(Mn,Fe)Si as well as fine Al6(Mn,Fe) particles were precipitated and a significant improvement in the elevated temperature properties was achieved. The addition of Ge promoted the precipitation of the θphase (metastable phase, θ-Al2Cu), due to the formation of GeSi precipitates, thereby improved the mechanical properties of the alloy after T6 heat treatment. However, the presence of these GeSi precipitates did not affect the coarsening of the θ phase to form Qphase( Al5Cu2Mg8Si6) during aging and, thus, the elevated temperature properties were not improved by the addition of Ge.

The sensitivity of a solid-state flux detector is studied using a 3mm × 3mm × 0.635mm size aluminum nitride piece. We describe the results of the gamma measurements in the high flux Co 60 irradiation facility and the neutron measurements in a beam port of the HANARO research reactor where the gamma flux is about 1% of the neutron. The measured results are compared with the calculated results based on the MCNP4B and EGS4 code. The current generated by the neutron flux is calculated by using the MCNP4B code and the current generated by the gamma flux is computed by using the EGS4 code. The calculation results for the expected current in the full power PWR nuclear power plants are included.