As aluminum (1S, 2S, etc.) has very low hardness and much toughness, it is so difficult to get a good finished surface by turning that it is considered as a comparatively non-cuttable material. The mechanism of orthogonal cutting of aluminum by low speed machining is discussed in this paper.
The following results were obtained.
In cutting of H-material, there was observed the transient phenomenon, i. e., the overrunning of cutting force, in the early stage of cutting. The cutting force gradually increased with the proceeding of operation and reached the maximum value; subsequently, it slightly decreased to a constant value, because of the formation of built-up edge on rake face, which adhered to the cutting edge and became steady. The above phenomenon was generally observed in orthogonal cutting of wrought aluminum alloys and it resulted in considerably good reproducibility. The cutting behavior of O-material was much different from that of H-material and it was found that the cutting phenomenon was rather complex and the force was irregularly changed with the lack of reproducibility. The deformation was rather plastic than shearing and the chips formation was like stick-slip motion. In cutting of 1/2 H-material, there was oberved an intermediate phenomenon between the above two materials.
It cannot be emphasized that the transient phenomenon, overrunning of cutting force, in the early cutting stage is peculiar to aluminum and its alloys. However, that phenomenon frequently occurred in aluminum and its alloys owing to the steadiness of built-up edge. The stabilizing condition of built-up edge was examined with respect to the energy for the growth of built-up edge which was supplied with frictional energy between chips and built-up edge.

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The aging behavior of duralumin (17S) and its difference from those of Al-Cu and Al-Mg₂Si alloys were investigated by means of a transmission electron microscope, tensile test, and hardness measurement. It was found that the aging process in duralumin up to the maximum hardness was almost the same as that in binary Al-4% Cu alloy, and subsequently occurred an aging process similar to that in Al-Mg₂Si alloys. The distribution of precipitates were much finely dispersed than those in the corresponding Al-4% Cu alloy. The finer dispersion of the precipitates were found to cause the maximum hardness of duralumin in high temperature aging.
Manganese, which is known to remove unfavorable effects of iron in this alloy, was found to form spherical particles of Al-Mn-Fe compound even in as-quenched state, and it was also found that precipitates were preferentially formed on these particles. The presence of these compound particles had no effects on essential process of aging, but it seemed to be favorable for grain refining. Aging at room temperature caused no change on structure when observed under an electron microscope. However, it allowed moving dislocations to yield irregular forms, which suggest that very fine and dense G. P. zones contributed to yield considerable hardening in room temperature aging.

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This paper reports macroscopic and microscopic metallography of aluminum and its alloys solidified in a cylindrical die under high hydrostatic pressure of 1000-6000kg/cm².
When the pressure was applied at 50-60°C higher than the melting temperature, columnar crystals, which had originated on the surface of die, easily developed towards the center of die, although other conditions were selected to allow the formation of equi-axed crystals under normal pressure. Less superheating, on the other hand, often generated a center zone of equi-axed crystals, and the zone was wider with the increase of pressure. Preferential linear growth of dendrite stems in columnar zone remarkably occurred under high pressure, and exclusion of solute to liquid side of solid/liquid interface was facilitated by the application of high pressure. It resulted in normal segregation in aluminum-silicon and aluminum-copper alloys. When the pressure was constant and the temperature at which pressure was applied was lower, the equiaxed zone was wider, and the crystals were finer by the effects of undercooling (accompanied by the rise of the melting temperature) and rapid cooling. It was found that pure aluminum solidified at 11°C higher than normal melting temperature under applied pressure of 1500kg/cm².

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In electrification work of railways, steel truss structure, having fabricated steel masts or concrete poles, is generally used for supporting overhead line. The structure shall need bearing capacity of soil amounting 10-20t/m² in order to support its weight and moment. However, in the electrificationwork of JNR Tohoku Line, it was found that the ground is as weak as 1t/m² in bearing capacity at Mutsuichikawa Station. In order to solve the problem mentioned above, the authors developed a light weight overhead line structure of 15m in span, constructed with shapes and plates of 6061-T6 aluminum alloy. The design and test results of the structure are reported in this paper.
The developed light weight portal structure is as light as 40% in weight as compared with that of the ordinary structures of the same class. As the results of tests at the actual spot, it was found to be durable to support the loads, which are to be expected by overhead line structure. The structure can endure uneven settlement of struts up to 312mm induced by the weak ground. However, its recovery after the settlement will easily be adjusted owing to its light weight.

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