An age hardening model for Al-7Si-Mg casting alloys

Yield strength (YS) ageing curves have been modelled for A356 and A357 aluminium casting alloys below the solvus temperature of the main hardening precipitate. Predictions are based on the Shercliff and Ashby methodology (Acta MetaH. Mater. 38 (1990) 1789) for wrought alloys. Differences between strengthening in wrought and cast Al-Si-Mg alloys are considered. A Brinell hardness to YS conversion incorporating strain hardening has been established to enable YS ageing curves to be predicted with reduced experimental effort. (C) 2002 Elsevier Science B.V. All rights reserved.

Monitoratge remot d'esdeveniments per al control i supervisió utilitzant "System on chip" i "w-USB"

Aquesta memòria descriu el procés de desenvolupament d'un projecte que consisteix en un conjunt de hardware, “PSoC” (Programmable System on Chip), i un software, C#, mitjançant els quals s'automatitza la gestió de comandes a les taules d'un restaurant. A cada taula trobem un aparell anomenat “WaiterClient”, a través del qual els clients sol·liciten l'atenció d'un cambrer. Aquest hardware té una pantalla on es mostrarà informació i un conjunt de polsadors per demanar. Per una altra banda, trobem un altre aparell, “WaiterServidor”, encarregat de rebre els senyals enviats per wireless des dels “WaiterClients” que hi ha a cada taula. Un cop rebudes, les transmet a un ordinador central per cable sèrie RS-232.

On the stability of the bcc phase in Cu-Al-Mn shape memory alloys

Measurements of the entropy change at the martensitic transition of two composition-related sets of Cu-Al-Mn shape-memory alloys are reported. It is found that most of the entropy change has a vibrational origin, and depends only on the particular close-packed structure of the low-temperature phase. Using data from the literature for other Cu-based alloys, this result is shown to be general. In addition, it is shown that the martensitic structure changes from 18R to 2H when the ratio of conduction electrons per atom reaches the same value as the eutectoid point in the equilibrium phase diagram. This finding indicates that the structure of the metastable low-temperature phase is reminiscent of the equilibrium structure.

Magnetoelasticity and magnetoresistance in Cu-Al-Mn shape-memory alloys

We study the effect of a magnetic field on the martensitic transition of a Cu-Al-Mn shape-memory alloy. The martensitic transition has been studied through resistance measurements under applied magnetic fields ranging from 0 to 50 kOe. Negative magnetoresistance showing an almost linear dependence with the square of the magnetization has been observed. This magnetoresistive effect is associated with the existence of small ferromagnetic Mn-clusters. Its strength and thermal dependence is different in both phases. The martensitic transition temperature is slightly increased and its spread in temperature significantly reduced upon increasing the field. These results show the existence of magnetoelastic coupling, which favors the nucleation of those martensitic variants with the easy magnetization axis aligned with the field.