Correlation analyses and multiple regression analyses by stepwise regression procedure have been performed on Mg-(2.5-7.8%) RE-(0-5.7%) Zn-(0.1-0.8%) Zr alloys unidirectionally solidified and T5-treated. Mechanical properties of the cast alloys are strongly affected by RE content. 0.2% proof stress and Brinell hardness increase and the other properties decrease with an increase of RE. Zinc has a significant effect on 0.2% proof stress of the T5-treated alloys. RE extremely influences on the other properties. 0.2% proof stress and Brinell hardness upgrade with increases in the centents of RE and Zn. The other properties degrade with increasing RE. Tensile properties and Brinell hardness are improved with increase in liquid cooling rate V_LC and Zr content. If the castings such as sand mold castings solidify at lower V_LC, it is required to select the alloy composition having high RE and Zn and to perform T5-tempering in order to surpass minimum tensile properties of JIS MC8 casting alloy. The alloy castings within JIS composition limit which are solidified at such a high V_LC as that in permanent mold castings have tensile properties exceeding JIS minimum values.

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The precipitation behavior during homogenization of DC cast aluminum alloy 1100 has been invesigated by means of electrical resistivity measurement and transmission electron microscopy. Precipitation is accelerated above 300°C and small AlFeSi precipitates (mainly of α-AlFeSi) are observed around 450°C, when ingot is heated up at a rate of 50°C/hr. The precipitates grow and disperse in matrix along with dissolution of α-AlFeSi, precipitation of Al₃Fe and probable transformation from α to Al₃Fe, when heated above 500°C or held at each temperature. Al₃Fe also precipitates at the interface between crystallized intermetallic compound and matrix above 550°C, and no precipitates exist in the matrix after prolonged holding at 600°C. In case where the ingot is cooled down at 20°C/hr and held after homogenization at 550°C the 3hr, precipitation progresses with almost constant distribution in matrix. The precipitates appear in matrix at lower temperature around 400°C and after prolonged holding below 500°C, when the ingots are cooled after heating at 600°C for 9hr.

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Natural corrosion potential of Al-Fe alloy which was corroded in aerated stirred NaCl (0.01M, 0.05M, 0.1M, 0.5M, 1.0M, 5.0M) solutions for an immersion period of 1000h has been studied in terms of electrochemical behavior. The conditional inequality between drop of natural corrosion potential; ΔE_cor and activities of Cl^- in bulk solution; a (Cl^-)_bulk is given as follows: ΔE_cor_??_0.09-0.10×loga(Cl^-)_bulk. It is confirmed that the data obtained satisfies the conditional inequality.

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The aging behavior of Al-4.4%Zn-1.5%Mg alloy affected by Li additions up to 2% was examined by means of hardness and electrical resistivity measurements, and transmission electron microscopy. The age-hardenability was diminished and improved with increasing Li content in the case of aging at low (<393K) and high (>393K) temperatures, respectively. This phenomenon was mainly attributed to the following facts: (1) the growth of Al-Zn-Mg ternary GP zones was retarded by Li addition; (2) Al₂LiMg and δ' (Al₃Li) phases as well as η (MgZn₂) or X phase formed in the Li-bearing alloys at high temperatures, and thus the volume fraction of precipitates increased with increasing Li content; (3) the δ' also formed at low temperatures, but did not greatly contribute to age-hardening. The limit Li content for δ' precipitation increased as the aging temperature increased, which is similar to the case in the Al-Li binary alloys.

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Alloys of Al-2.2%Cu-1.5%Mg with equal amounts of Fe and Ni addition up to 7% each were argon gas-atomized to fine powders, and continuously extruded by a Conform machine. The extrudates showed superior strength, heat resistance and high modulus of elasticity and also exhibited low thermal expansion coefficients and good wear resistance. The extrudates from rapidly solidified alloy powders were dispersion hardened by fine dispersoids of Al₉FeNi and age hardened by Al-Cu-Mg precipitates. High volume fraction of Al₉FeNi phase also caused high modulus, low thermal expansion and good wear resistance.

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Properties of Ar gas atomized powders of Al-8mass%Fe alloy and its variation by annealing have been examined by means of scanning electron microscopy, transmission electron microscopy and hardness measurement. A cell structure having metastable phase Al_mFe at its boundaries forms in particles in the size smaller than 105μm, besides a primary crystallized intermetallic compound Al₃Fe predominantly exists in the particles larger than 105μm. The hardness of powders increases with decreasing particle diameter due to the refinement of cell structure. The annealing at temperature above 400°C accelerates the decomposition of cell structure and the formation of granular intermetallic compound, both of which result in the notable softening in the small size particles. Al_mFe which has been at cell boun dariestransforms to Al₃Fe by the annealing above 450°C. Even after high temperature annealing, large particles show only a slight decrease in hardness keeping low values due to a small change in the coarse structure.

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