Solid solubility of titanium in aluminum was determined by measuring electrical resistivity of the Al-Ti alloys equilibrated for a sufficiently long period. The solid solubility is 0.71 wt% (0.40 at%) at 550°C, 0.96 wt% (0.54 at%) at 600°C and 1.24 wt% (0.70 at%) at 640°C. The maximum solid solubility of titanium in aluminum 1.32 wt% (0.75 at%) at peritectic temperature of 665.2°C is determined by extrapolating the above data. All of the solid solubilities in the preceding informations are lower than those in this work probably by reason of insufficient equilibration.

View full abstract

Bauxite was chlorinated in molten salts using chlorine gas and carbon to produce Alcoa Electrolyte such as AlCl₃-NaCl-KCl melt. Chlorine gas was mildly introduced at 820°C into the suspension of bauxite and carbon powder in NaCl-KCl eutectics. AlCl₃-FeCl₃-NaCl-KCl melts are obtained without significant loss of AlCl₃, carbon and chlorine gas. Hematite in bauxite dissolves in molten NaCl-KCl salt. Chlorination of alumina is enhanced by ferric chloride. Selective chlorination of bauxite is performed with hydrogen chloride gas and carbon in NaCl-KCl salt bath to give FeCl₂ not FeCl₃. The selective chlorination to remove hematite as FeCl₃ is also achieved when a large amount of bauxite is introduced in a small amount of molten salt.

View full abstract

The origin of abnormal structures and layers formed in practical ADC12 alloy die castings 1 to 22kg in weight is studied by measuring molten metal temperatures in a shot sleeve of die casting machines. The molten metal poured into the shot sleeve rapidly cools down to the eutectic temperature and is injected into a die cavity in the solid-liquid mixture state. When the plunger tip runs through the shot sleeve, solidified layers on the inner wall of the sleeve are peeled off and mixed into the flowing liquid. The solid layers are disintegrated and conveyed into the die cavity to form scattered structures in die castings. The primary aluminum phase already crystallized in the shot sleeve grows into coarse dendrites in die castings.

View full abstract

The Al-4mass%Cu-(04.5)mass%Cr alloys were prepared by chill-casting, and their heat-resisting properties were examined. The amount of solute Cr quenched in Al-4%Cu alloy was about 1.5% at maximum. Resistance to over-aging was markedly increased with increasing amount of solute Cr, when the alloys were subjected to usual heat-treatments: that is, homogenization at 793K after chill-casting, water-quenching, aging at 473K and subsequent over-aging at 623K. This phenomenon would mainly be attributed to the fact that θ' formed during pre-aging became very stable both in the amount and the size, as the amount of solute Cr increased. The chill-cast Al-4%Cu-2%Cr alloy was thought to be superior to commercial heat-resisting 2219 alloy. The over-aged structures of Cr contained alloys were in detail discussed, in comparison with those of Mn contained alloys.

View full abstract

The stretch formability of aluminum sheets for heat-exchangers was investigated. The formability in stretch-flanging and ironing of plate-fins is estimable by a hole-flanging test. A definite correlation lies between the stretch-flanging formability of a pierced hole and local elongation of cold rolled sheets. Stretch-flanging of the pierced hole is almost independent of r-value, n-value and elongation of cold rolled sheets. Local elongation of cold rolled sheets is enlarged when the cell structure transforms to the subgrain structure by recovery and is refined by recrystallization. The sheets having refined subgrain size and grain size allow large local elongation. The subgrain size which corresponds to the cell size is refined by Al₃Zr precipitates uniformly dispersed in cold rolled sheets. Burr deteriorates stretch-flanging on a pierced hole to a greater degree. The formability is improved by eliminating burr and fructure zones, where the uniform elongation is a potential factor.

View full abstract

The effect of iron content on the plane strain fracture toughness K_IC in the high strength Al-Zn-Mg-Cu alloy was investigated using four model alloys which have nominally identical composition except for their iron contents of 0.0, 0.2, 0.4 and 0.6%, and the acoustic emission technique was applied to examine the fracture processes. K_IC increased with the reduction in iron content, while the yield strength, tensile strength and the elongation were approximately constant. The scanning electron fractography and the electron-probe-micro-analysis (EPMA) revealed that iron formed the coarse and brittle inclusions which are easy to debond and crack. The measured K_IC agreed well with that evaluated from the ductile fracture model in which K_IC corresponds to the coalescence of voids nucleated at those inclusions.
The cracking of inclusions and the micro pop-in prior to the main crack growth (K_IC) were monitored as the major sources of small and large amplitude acoustic emission, respectively, and it was verified that acoustic emission analysis in terms of amplitude measurement is useful for the real-time classification of the fracture processes such as void nucleation and their coalescence.

View full abstract