The effect of temperature on the sequence of hardening precipitates in Al-1·15Mg2Si-0·34Cu-0·21Cr (wt-%) balanced and Al-1·14Mg2Si-0·34Cu-0·21Cr (wt-%) alloys with excess Si has been investigated by hardness measurement (HV), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) techniques. The values of microhardness which are corresponding to the hardening precipitated particles in the alloy containing excess Si are higher than that in the alloy without Si. The results showed that, the difference in the hardening precipitation peak positions may match the fact that, the excess Si increases the density of β" metastable phase and also, reduces the Mg/Si ratios in the early stage of GP zones and co-cluster formation. After the complete formation of the metastable needle shaped precipitates β" takes place, the strengthening of the alloy would take place as a result of the formation of the semicoherent rod shaped precipitates β' and/or Q' phases.

The thermoelectric power (TEP) and the electrical resistivity (ER) of Al-Mg-Si (balanced) and Al-Mg-Si-Cu (balanced + Cu) alloys have been measured in the temperature range 300-800 K. TEP and ER are found affected by different types of precipitates in the Al matrix. Addition of Cu refined the microstructure of the balanced alloy hence altered the TEP and ER measurements. Cu promotes the kinetics of artificial aging due to the formation of the Q' phase and the intermediate phases which precipitate at earlier temperatures. The coexistence of the equilibrium (3 (Mg2Si) and the stable Q-phases results in stabilization of the TEP at elevated temperatures. The existence of Cu slightly increases the lattice rigidity leading to a decrease in the rate by which the ER increases with temperature. Repeating measurements after slow cooling of the two alloys changed considerably the results of TEP and ER. Correlation was found between different types of precipitates and changes in the TEP and ER indicating the possibility of employing TEP and ER measurements to study the precipitation sequence in such alloys.

The thermoelectric power (TEP) and the electrical resistivity (ER) of Al-Mg-Si (balanced) and Al-Mg-Si-Cu (balanced + Cu) alloys have been measured in the temperature range 300-800 K. TEP and ER are found affected by different types of precipitates in the Al matrix. Addition of Cu refined the microstructure of the balanced alloy hence altered the TEP and ER measurements. Cu promotes the kinetics of artificial aging due to the formation of the Q' phase and the intermediate phases which precipitate at earlier temperatures. The coexistence of the equilibrium (3 (Mg2Si) and the stable Q-phases results in stabilization of the TEP at elevated temperatures. The existence of Cu slightly increases the lattice rigidity leading to a decrease in the rate by which the ER increases with temperature. Repeating measurements after slow cooling of the two alloys changed considerably the results of TEP and ER. Correlation was found between different types of precipitates and changes in the TEP and ER indicating the possibility of employing TEP and ER measurements to study the precipitation sequence in such alloys.

The thermoelectric power (TEP) and the electrical resistivity (ER) of Al-Mg-Si (balanced) and Al-Mg-Si-Cu (balanced + Cu) alloys have been measured in the temperature range 300-800 K. TEP and ER are found affected by different types of precipitates in the Al matrix. Addition of Cu refined the microstructure of the balanced alloy hence altered the TEP and ER measurements. Cu promotes the kinetics of artificial aging due to the formation of the Q' phase and the intermediate phases which precipitate at earlier temperatures. The coexistence of the equilibrium (3 (Mg2Si) and the stable Q-phases results in stabilization of the TEP at elevated temperatures. The existence of Cu slightly increases the lattice rigidity leading to a decrease in the rate by which the ER increases with temperature. Repeating measurements after slow cooling of the two alloys changed considerably the results of TEP and ER. Correlation was found between different types of precipitates and changes in the TEP and ER indicating the possibility of employing TEP and ER measurements to study the precipitation sequence in such alloys.

The thermoelectric power (TEP) and the electrical resistivity (ER) of Al-Mg-Si (balanced) and Al-Mg-Si-Cu (balanced + Cu) alloys have been measured in the temperature range 300-800 K. TEP and ER are found affected by different types of precipitates in the Al matrix. Addition of Cu refined the microstructure of the balanced alloy hence altered the TEP and ER measurements. Cu promotes the kinetics of artificial aging due to the formation of the Q' phase and the intermediate phases which precipitate at earlier temperatures. The coexistence of the equilibrium (3 (Mg2Si) and the stable Q-phases results in stabilization of the TEP at elevated temperatures. The existence of Cu slightly increases the lattice rigidity leading to a decrease in the rate by which the ER increases with temperature. Repeating measurements after slow cooling of the two alloys changed considerably the results of TEP and ER. Correlation was found between different types of precipitates and changes in the TEP and ER indicating the possibility of employing TEP and ER measurements to study the precipitation sequence in such alloys.

optical absorption measurements are carrird out on as-deposited and thermal annealed SeTeSbfilms. the annealed films show an increase in the optical enerergy gap with increasing temp. of annealing.

In this paper, the effects of variable viscosity and thermal conductivity on coupled heat and
mass transfer by free convection about a permeable horizontal cylinder embedded in porous
media using Ergun mode are studied. The fluid viscosity and thermal conductivity and
are assumed to vary as a linear function of temperature while the mass diffusion is
assumed to vary as linear function of concentration. The surface of the horizontal cylinder
is maintained at a uniform wall temperature and a uniform wall concentration. The transformed
governing equations are obtained and solved by using the implicit finite difference
method. Numerical results for dimensionless temperature and concentration profiles as
well as Nusselt and Sherwood numbers are presented for various values of parameters
namely, Ergun number, transpiration parameter, Rayleigh and Lewis numbers and buoyancy
ratio parameter.