The fatigue strength of 5083-R and 5083-O sheet specimens of 6mm thickness having artificial scratches at the middle part was investigated. The scratch was made by scraping with a tool, having a tip angle of about 80° and a tip radius of about 0.02mm.
As the results of tests, the effect of scratches on the fatigue strength was not found for the scratch depth less than 0.06mm for 5083-R specimens and less than 0.10mm for 5083-O, and fatigue fracture always occurred at the other part than the scratches. For the specimens with the scratch depth more than the above mentioned, fatigue failure was initiated at the surface scratches and their fatigue strength was slightly decreased with increasing the scratch depth. The effect of the angle between the scratch and the direction of the alternating stress on the fatigue strength was not found from the fatigue tests of 5083-O specimens with the scratch depth less than 0.2mm.

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Thermal analyses of Al-Si alloys were carried out in order to investigate the effect of the primary phase as a site of heterogeneous nucleation for eutectic solidification.
Thermal analyses on Al-Ge and Sn-Pb alloys were also performed to support the discussions on the results of Al-Si alloys.
The results obtained were as follows.
(1) For the case of Al-Si alloys, larger undercooling was needed for nucleation of the eutectic phase when primary Si rather than primary Al was present in the melt.
(2) For the case of Al-Ge alloys larger undercooling was needed for nucleation of the eutectic phase when primary Al rather than primary Ge was present in the melt.
(3) For the case of Sn-Pb alloys, negligible undercooling was needed for nucleation of the eutectic phase when primary Sn was present in the melt. In contrast, large undercooling was obtained when primary Pb was present in the melt.
Using experimentally obtained and calculated values of interfacial energies for boundaries of liquid-primary, liquid-secondary and primary-secondary phases, the energy balances for heterogeneous nucleation were calculated and the present experimental results were found to be compatible with the calculated results.

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Some mechanical properties of Al-Zr alloys (-0.3wt%Zr)were investigated by the static tensile test at -30-150°C and by the creep test at 150°C.
The results obtained are summarized as follows:
(1) Any fundamental difference between Al-Zr alloys and pure aluminum was not observed by the static tensile test. In all cases, tensile strength is higher by about 3kg/mm² at-30°C than 150°C, and elongation value of cold rolled specimens is also higher at lower temperature, except the case of pure aluminum in which it increases again at 150°C due to recrystallization softening.
(2) The general tendencies above mentioned are hardly changed by pre-aging treatment before cold working. But it is interesting that age-hardened alloys do not show a decrease of ductility and their elongation values increase somewhat.
(3) Pre-aging treatment for a very short time is most effective to decrease the steady-state creep rate at 150°C for cold rolled specimens. Treatment at higher temperature for a long time is not effective but detrimental, even if under age-hardened conditions.
(4) Creep-resistance properties at 150°C of Al-Zr alloys are governed by thermal stability of the cold worked structure and different somewhat from recrystallization behaviors at higher temperature, where some stable precipitates are necessary for prohibiting subgrain boundary migration. In the former case, slight segregation of Zr atoms on the dislocations seems to be sufficient for decreasing the steady-state creep rate.

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