Increasing the ductility of the Al-Si alloy with low silicon content by deformation-heat treatment

A method of deformation-heat treatment is considered for Al-Si alloy with 4.5 % silicon, which consists in a series of small hot deformations with intermediate annealing. The proposed method allows one to achieve grinding and spheroidization of silicon inclusions, which in the cast state have the form of lamellar excreta at the grain boundaries and significantly reduce the plasticity of the material. Spheroidization, grinding and mixing of inclusions that are achieved during this deformation-heat treatment lead to significantly increase the ductility of the alloy without loss of hardness. The processes of structure change during the deformation of aluminum alloys with low Si content are insufficiently studied. In particular, of interest was the possibility of increasing the ductility of such materials by grinding and mixing silicon inclusions during hot deformation. In this case, to prevent a decrease in ductility due appearance of microconcentrators of stress in the form of acute angles of the crushed silicon inclusions, the deformation was carried out as a series of stages with intermediate annealing. In addition, it was assumed that the cyclic change of temperature in this mode will contribute to the spheroidization of fragments of crushed silicon inclusions by changing the solubility of silicon in solid solution from temperature. It is shown that the proposed mode of deformation-heat treatment of these alloys of the Al-Si system allows to significantly increase their ductility – the critical degree of deposition (deposition before cracking) from 67.8 % in the cast state to – 92.1 %. The hardness of the material can be increased by hardening under cold plastic deformation. In this case, since the material after deformation-heat treatment is more plastic, it has greater reserves for hardening in this way. It is shown that owing to hard plastic deformation, the hardness of the material of samples with 4.5 % Si, which has undergone deformation-heat treatment, can increase to values of 95 ± 17 HV, which is significantly higher than in the cast state. At the same time, the hardness (and, probably, strength) of a similar cast material can also be increased due to hardening, but to lower values – 67 ± 12 HV. Key words: aluminum, aluminum-based alloy, deformation-heat treatment, silicon inclusions, plasticity, hardness.

Joints Properties of Aluminum Foams/Aluminum Plate by Transient Liquid Phase Bonding Process

Aluminum foams/aluminum plate was transient liquid phase diffusion bonded with Cu/Al/Cu composite interlayer, then the investigation on joint microstructure, element diffusion and joint strength was conducted at 565°C. The results showed that, there was a significant grain boundary penetration phenomenon near the interface and it was more seriously at the side of aluminum foams. The XRD results showed indicated that the main phases near the interface were α-Al, CuAl2, AlCu, Al4Cu9, Al2O3. By EDS line scanning, it indicated that the diffusion behavior of elements was different at three regions, compared with the edge region, the interface of the central region was better and the depth of element diffusion is larger, at the pore region, the liquefaction of interlayer was not successfully and the morphology was lamellar. Mechanical properties test showed that the largest shear strength of joint was 4.61 MPa when the duration was 40 min. Key words: Aluminum foams; transient liquid phase bonding; microstructure; element diffusion; shear strength

NEW ALUMINUM ANTIFRICTION ALLOYS INSTEAD OF BRONZES FOR MONOMETALLIC BEARINGS OPERATING UNDER CONDITIONS OF BOUNDARY FRICTION

In the paper there is presented an investigation on the subject of the substitution of materials used for manufacturing monometallic one-piece sliding bearings. The most widely used material for their manufac-turing is bronze of BrO4Ts4$17 grade which has rather high values of antifriction and strength properties. A whole complex of materials based on aluminum alloys is under consideration. There were investigated eight experimental alloys different with chemistry. In the paper there is described a procedure for carrying out experimental investigations. The comparative tables of the influence of these or those elements upon tribological properties are shown. An evident advantage of aluminum alloys over a compared material – bronze of BrO4Ts4S17 grade is identified. The following tribo-technical properties of experimental alloys such as score-resistance, conformability, durability, frictional moment are considered. Key words: aluminum antifriction alloys, bronze, stress-strain properties, strength, hardness, tribotechnical properties, conformability, scoreresistance, durability, secondary structures.

The relative importance of oxalate and pyrophosphate extractable aluminum to the acidic leaching of aluminium in Podzol B horizons from the Precambrian Shield, Ontario, Canada

Four Bf and one Bhf Podzol horizon samples from the Precambrian Shield, Ontario, Canada were leached with pH 3 solutions in three different experiments to determine which soil aluminum fraction was primarily responsible for the aluminum leached into solution. For the Bf horizons, it was primarily the oxalate-extractable aluminum fraction (corrected for pyrophosphate, Alo–Alp); for the Bhf horizon it was equally the pyrophosphate (Alp) and Alo–Alp. A comparison with other studies suggests that when the ratio (Alo–Alp)/Alp is above 0.3–0.7, the oxalate-extractable fraction will be most important, and at lower ratios the pyrophosphate fraction becomes most important. The pattern of fluoride leaching in these experiments suggests that F was concentrated primarily on the surface of the amorphous aluminum fraction. Key words: Aluminum, silica, fluoride, Podzol, acid deposition

The influence of pH on the toxicity of a low concentration of aluminum to white spruce seedlings

Week-old white spruce seedlings were grown for 7 days at pH 4.5, 3.9, 3.65, or 3.5 using a continuous flow system to deliver experimental solutions. At each pH, seedlings received either no aluminum or 10 μM Al, a concentration 2 – 3 orders of magnitude lower than the reported minimum Al concentrations required to induce toxicity symptoms in seedlings of a variety of tree species. In – Al treatments, root elongation was reduced at pH 3.9 and root dry weight was reduced at pH 3.5, compared with seedlings grown at pH 4.5. Exposure to 10 μM Al caused further reduction of root growth, the magnitude of which increased as pH decreased. This suggests that seedling root growth was affected by the increased proportion of the total Al existing as phytotoxic Al3+ at lower pH values or by an interaction of Al3+ and H+. Neither pH nor Al affected shoot growth. Both acidity and Al could limit natural regeneration of white spruce by preventing seedling establishment. Key words: aluminum toxicity, soil acidity, forest decline, white spruce, Picea glauca, forest regeneration.

INFLUENCE OF PHOSPHATE IONS ON THE EXTRACTION OF ALUMINUM BY 8-HYDROXYQUINOLINE FROM OH-AL SUSPENSIONS

Aluminum was extracted from OH-Al-suspensions ([Al3+] = 6.4 × 10−4 mol L−1; OH/Al molar ratio = 1.0, 1.5, 2.2) aged 5 and 18 mo by 8-hydroxyquinoline into four different species: readily extractable (Alre), moderately ex tractable (Alme), slowly extractable (ALse) and nonextractable (Alne) aluminum. In all the systems, the percentages of Alre were the highest of the ultrafiltered hydrolytic products of Al, ranging from 68.1 to 21.1%, whereas the percentages of Alme and Alse were [Formula: see text]. The higher the OH/Al molar ratio and the longer the aging period of OH-Al-suspensions, the lower the percentages of Alre, Alme and Alse, and the higher the percentages of Alne (ranging from 13.3 to 71.1%). With addition of phosphate ions, increasing the P/Al molar ratio from 0.05 to 0.5 decreased Alre and increased Alne. Finally, it was ascertained that the ultrafiltered aluminum was not completely extracted by 8-hydroxyquinoline after 3 h. More aluminum was extracted from 3 to 48 h from the suspensions containing phosphate ions than from those without phosphate. Key words: Aluminum hydrolytic products, phosphate, aluminum extraction, 8-hydroxyquinoline

INFLUENCE OF SUBSOIL ACIDITY ON ROOT DEVELOPMENT AND CROP GROWTH IN SOILS OF ALBERTA AND NORTHEASTERN BRITISH COLUMBIA

Experiments were conducted in the field and greenhouse with soils of Alberta and northeastern British Columbia to determine the influence of subsoil acidity on acid-sensitive crops. Experiments involved liming of only the topsoil, liming of both topsoil and subsoil, and measuring the aboveground crop yield and the yield of roots in the topsoil and subsoil. In both field and greenhouse, subsoil acidity reduced the yields of top growth and subsoil root pernetration for both barley and alfalfa. The reductions in yield of top growth and roots in the subsoils were correlated closely with the amount of Al (extractable in 0.02 M CaCl2) in the unlimed subsoil. Lowering the soil temperature did not reduce root growth more in acid soils than in limed soil. There were five field experiments, and in the three of these which had subsoils high in extractable Al, the limed subsoils had less moisture at the time of harvest than the unlimed subsoils. The damage to crops caused by subsoil acidity was eliminated by deep liming or in one case by large applications of P to the subsoil or topsoil. These methods of correcting subsoil acidity would not be economically feasible on a field scale. A preliminary field survey was conducted to delineate agricultural areas where subsoil acidity (based on soil pH and extractable Al content) is a significant problem. The largest areas were found in northwestern Alberta and northeastern British Columbia. Key words: Aluminum toxicity, subsoil acidity, liming, temperature, phosphorus, barley