The specific electric conductivities of ternary moten salts of NaF-BaCl₂-AlF₃ and NaF-BaF₂-AlF₃ systems for electrolytic refining of aluminum were measured and were reported in the previous paper.
The results were discussed and the following conclusions were drawn.
(1) The specific electric conductivites of the binary NaF-BaCl₂ molten salts were calculated by "Taniuchi's modified formula, " which is the modification of "Markov's formula." The calculated values corresponded with the measured values very well.
Then, the specific electric conductivities of the binary NaF-BaF₂ molten salts over the whole range of composition were calculated by the above formula.
(2) The measured values of the conductivities of the ternary molten salts of NaF-BaCl₂-AlF₃ and NaF-BaF-AlF₃ systems were very different from the values expected from each binary molten salts composing the ternary systems; the former were very lower than the latter.
The final conclusion was as follows: These ternary molten salts are not simple ionic melts, but are composed of several complex ions in molten state. It would be the reason of the fact that the measured values of specific electric conductivities of the ternary molten salts were very lower than the values expected from those of each binary molten salts composing the ternary systems.

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In order to investigate the effects of the grain refining of pure aluminum (99.99%) and its alloys (with copper, magnesium, zine, silicon, manganese, and nickel), powder of a carbide such as TiC, TaC, WC, TaC-WC, NbC and VC was added to the former metal or alloys. Chiolite was also added as a flux to prevent the oxidation of the carbide. The molten alloys containing the carbide and chiolite were thoroughly stirred in a crucible and slowly allowed to cool. The influences of remelting and holding of the alloys at a high temperature were investigated. The average diameters of the grains were measured in macro-and micro-structures of the specimens. Some of the specimens were investigated with X-ray micro-analyzer.
The results obtained were as follows.
(1) Powders of TiC, TaC, TaC-WC, NbC and VC were very effective in grain refining of pure aluminum and its alloys. The effects of TiC, TaC and TaC-WC were almost kept constant at a high temperature, and the growth of grains in size was not seen after holding at that temperature.
(2) The effects of TiC, TaC, and TaC-WC were very remarkable as compared with other carbides. The effects of NbC and VC came second, and that of WC was the least.
(3) Very effective agents for grain refining were obtained when the carbides were under the following conditions at the same time:
(a) Large free energy for formation
(b) Small density
(c) Crystal structure of NaCl type and small size factor for aluminum.

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The effects of small amounts of an additional element (Ag, Si or Zn) on the creep characteristics of Al-6.3at% Mg alloys were investigated for the specimens which had been subjected to two kinds of heat-treatments.
The heat-treatment (A) was an attempt to obtain dispersed coarse particles. The specimens were solution heat treated at 400°C for 1hr. and furnace-cooled to 250°C at a cooling rate of 25°C/hr. Then, they were maintained at that temperature for 6 days and water quenched.
The heat-treatment (B) was to produce dispersed fine particles by much nucleation. The specimens were solution heat treated at 400°C for 1hr. and water quenched. Then, they were maintained at 150°C for 2 days, at 200°C for 2 days, and at 250°C for 6 days, and then again water quenched. The heat treatments had remarkable effects on the creep characteristics such as activation energy (Q) and stress exponent (n) expressed in the following state equation of steady creep;ε_s=Aσⁿexp(-Q/RT)
The activation energy (Q) and the stress exponent (n) for the creep at 250°C of the specimens heat-treated by (A) method were about 37kcal/mol and about 3, respectively. These values were approximately equal to those of Al-4.4at%Mg solid solution alloys. On the other hand, the activation energy and the stress exponent for the specimens heat-treated by (B) method were 2731kcal/mol and about 4 respectively, under the same testing conditions. The rate controlling step of the former treatment (A) would be the dragging of solute atmospheres around the jogs in screw dislocations and that of the latter treatment (B) would be due to the cross slip of dislocations. The difference between the effects of both treatments would be attributed to the change in transition temperature range from the cross-slip mechanism to the vacancy controlling mechanism.
The three kinds of additional elements had little effects on the high temperature creep characteristics of Al-6.3at%Mg alloys. It would be attributed to the fact that the additional elements had been dissolved in β phases of Al-Mg alloys during the heat treatments before the creep.

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Aluminum casting alloy AC4 (JIS) has widely been used in the parts of machines and automobiles because of its high castability, weldability, and shock resistance. A new kind of alloy, AC4D in Al-Si-Cu-Mg system, was admitted to JIS (Japan Industrial Standard) aiming at a higher degree of reliability. Its composition is prepared by blending of copper and magnesium with AC4, and it has lower silicon content as compared with the latter for the purpose of obtaining ability for heat treatment. The relation between casting conditions and mechanical properties, mass effects, effects of heat treatment, etc. of AC4D has thoroughly been studied. However, its data on machining (especially, on machinability) have still remained unsolved.
In this study, the machinability of AC4D was researched mainly by turning tests. The following results were obtained.
(1) The cutting resistance and cutting temperaure of AC4D were lower than those of AC4A and AC4B. Consequently, its tool life in machining was slightly longer.
(2) However, when it was machined with a cutting tool of high speed steel, the wear of tool, especially for 4DT6, was not negligible; and the finished surface was made worse with the progress of the tool wear. Whereas, the clips were in finely sheared form, which was not troublesome in treatment. Thus, it was concluded that AC4D has fairly high machinability.

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Continued from the previous paper, which discussed the effects of various kinds of heat treatments on machinability of cast alloy, AC4B, this paper describes the test results of cutting resistance, tool life, surface roughness, chip form, etc. on aluminum cast alloys; AC2B, AC8A, Al-4Zn-5Mg alloy, and Al-3Zn-3.5Mg alloy: and compares the machinabilities of T6-treated materials of these alloys with those of as cast, F-materials.
The results obtained were as follows.
The cutting resistance of T6-materials were generally higher than those of the corresponding F-materials. However, the difference between the both was very little in Al-Zn-Mg alloys. Cutting resistances (in particular, traversing forces) of T6-materials of AC2B and AC8A for a cutting tool of high speed steel were increased with the progress of time at a cutting speed higher than a certain value.
There appeared an oxidelike-deposit on the tool flank. The aspects of the deposits were different between T6-and F-materials, and the amount of deposit was very small in Al-Zn-Mg alloys.
The tool wear was not negligible for AC2B, AC4B, and AC8B; and for T6-materials, it was rapidly increased after a certain degree of time. Whereas, it was very little for Al-Zn-Mg alloys.
In general, the surface roughness of F-materials was more excellent with the higher cutting speed. However, the effects of cutting speed was less on T6-materials to obtain considerably smooth surfaces. It was also found that there was very little trouble in chip treatment.

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