Measurements of electrical resistivity and intensity of small-angle X-ray scattering and transmission electron microscopy were made on several compositions of Al-Zn alloys. G. P. zones are formed above the spinodal temperature in the nucleation-and-growth mechanism. The nucleus has a critical size for growth. This size becomes larger when aged at higher temperatures. The G. P. zones formed in this mechanism distribute broadly, but those formed by the spinodal decomposition do closely. The number of G. P. zones is much larger in the latter case (127°C) than that in the former (132°C). The spinodal temperatures estimated for Al-10.0, 12.5, 15.0 and 20.0wt% Zn alloys are 90-95°, 105-110°, 125-130° and 170-180°C respectively. The critical temperatures below which G. P. zones are observed in these alloys are 105-115°, 125-135°, 150-160° and 200-210°C respectively.

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The coarsening behavior of Si precipitates in Al-Si alloys containing 0.60, 0.90 and 1.19wt% Si was studied electron microscopically. The coarsening data of the alloys aged at 573 to 773K were analyzed on the basis of the Lifshiz-Wagner theory on diffusion-controlled coarsening. The coarsening kinetics of the Si precipitates follows the time-law predictions of the theory at all ageing temperatures. The particle-size distribution of the Si precipitates is significantly broader than the theoretical one. The activation energy for the Ostwald ripening and the particle matrix interfacial free energy were determined.

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The electric resistivity of Al-Si alloys annealed at various temperatures for a sufficient time to complete precipitation of Si phase and air cooled was measured at 77K. The solid solubility of Si in aluminum varies from 0.86 at% at 773K to 0.14 at% at 623K. The excess entropy of mixing and the heat of mixing on the basis of temperature dependence of the solid solution are 7.24 R and 47.7kJ/mol respectively. The residual resistivity for Si in aluminum is(6.7±0.1)×10^-9Ωm/at%. The electric resistivity of Al-Si alloys containing 0.60, 0.90 and 1.19wt% aged at 523 to 673K was measured at 77K to determine the variation of Si concentration in the matrix due to coarsening of the Si precipitates. The Si concentration in the matrix linearly decreases with t^-1/3. The C_e value and the Si concentration in equilibrium with a Si particle of infinite size are given. These data were applied to obtain reliable values of the particle-matrix interfacial free energy and the "effective diffusivity" of the solute in the matrix.

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An electro magnetic servo damper has been developed to overcome chatter in machining. This paper introduces it and describes its applications to machining aluminum alloys, carbon steel and superplastic materials. Various types of chatter are encountered in machining these materials having different machinabilities in accordance with their compositions. Machining tests were carried out to determine a chatter saving system of this damper. The modal damping of the structure is improved so successfully to stabilize usual machining by use of the damper. Such a system is, however, restricted in machining the materials of poor machinability.

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A metallographic work was carried out of Al-Ti and Al-Cu alloys (partition coefficient k; 7.8 and 0.17 respectively) unidirectionally solidifing in <100>, <110> and <111> directions. Cell-dendrite transition is governed by the heat flow direction and constitutional undercooling. Dendrite arms branch from cells at an early stage along the heat flow not in the <100> prefered growth orientation. The growing arms gradually shift toward the prefered orientation with increase in C₀•R/G. Branching and growth of the branched arms delay, when the prefered orientation is at a large angle to the heat flow. Pronounced constitutional undercooling accelerates the branching and the growth of branched arms. Characteristic transition behaviors in <100>, <110> and <111> directions are described in detail.

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Up and down milling test on annealed aluminum plates were carried out using a flycutter. The hardness of the deformed layer, compressive residual stress on and near the machined surface, surface roughness and maximum cutting resistance linearly increase with increase in feed per tooth. If the nose radius exceeds a certain limit in low speed cutting, the radius has a slight effect on the characteristics of the machined surface of the built-up edge. The hardness of the deformed layer and the cutting resistance increase and the surface roughness reduces with increase in the nose radius in high speed cutting. The residual stress distribution is nearly independent of the nose radius particularly in up milling. The up milling leads to a harder deformed layer. This is probably attributed to the difference of the fluidized layer near the machined surface. The down milling ensures more fine and favorable surface roughness and more of the residual stress.

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