Advanced Materials Research Vols. 602-604

Abstract: Sacrificial anodes performance of three iron alloys was measured by constant current test, The protection effects of iron alloys, zinc alloy and aluminum alloy sacrificial anodes on copper tube were compared and analysed by polarization test. The results show that all three iron alloys appearing well sacrificial anodes performance, with steady working potential, high practical electric capacity and current efficiency, the corrosion is uniform and the corrosion products fall easily. Iron alloys are more suitable for application on the cathodic protection of copper tube due to their more suitable driving voltage and coulpling current compared with zinc alloy and aluminum alloy.

Abstract: This paper studies the coupled effects of alloy elements for precipitation strengthening to rupture life of single crystal Ni-based superalloys. Through setting up the Radial Basis Function model to predict rupture life, the generalization ability test indicated that this model has better precision and practicability. According to this model, utilizing the theory of parameter sensitivity analysis to quantitative analysis the interactive effects of different alloy elements and/or groups to rupture life, providing the theory basis and reference for the alloy design and productivity of single crystal Ni-based superalloys.

Abstract: A flux with MnCl₂ is used to control the morphology of microstructure in Al-1Fe alloys. An orthogonal test plan (L(3³)) was employed to study the effect of the ratio of Mn/Fe, temperature and holding time on the morphology of the Fe-rich phase. Metallographic and image analys is techniques have been used to quantitatively examine the microstructural changes occurring with Mn addition. XRD analysis is employed to identify the phase of intermetallic compound in the alloy. It is found that when the ratio of Mn/Fe in the melt is located in the range from 1.5 to 2.0, the original needle like iorn phase can be transformed to be massive morphology, such as Chinese script, globule or polyhedral, and the area fraction of iron phase in the Al-1Fe alloy can be reduced by adding MnCl₂ during the melt processing.

Abstract: Laboratory researches of cooling rate influence on matrix structure, composition and quantity of nonmetallic inclusions in iron-aluminum alloys, containing 25-33%Al, are conducted. Thermodynamic modeling of composition and quantity of phases, which were formed in alloy system, containing Fe-Al-Si-C-O, for equilibrium conditions by means of the program complex ASTRA-4 (TERRA) is carried out. It is established, that irrespective of cooling rate the matrix has structure of intermetallic Fe-Al, and nonmetallic inclusions have platelet shape and composite of iron and aluminum oxy-carbides. It is confirmed, that ferroalloy with the optimal structure, necessary for receiving the high heat-resistance cast iron, should be cooled after smelting with the highest speed in these condition.

Abstract: In order to develop a high-strength aluminum alloy, alumina dispersion strengthened aluminum alloy was prepared by high energy ball milling on 2024 aluminum alloy powder in ethanol. The microstructure, particle size and distribution of the Al2O3 particles in the alloy were analyzed by FE-SEM; the mechanical properties were investigated. Results showed that alumina dispersion strengthened aluminum alloy was prepared successfully by high energy ball milling, the Al2O3 particles of several tens of nm in diameter were homogeneously distributed in the matrix grain and the spatial distance between particles was about 50-100nm. The yield strength and elongation of alumina oxide dispersion strengthened aluminum alloy were 489MPa and 7.9%.

Abstract: The microstructure and mechanical properties of AZ61-4Si magnesium alloy before and after equal channel angular processing (ECAP) were studied. Results show that the matrix α-Mg and divorced eutectic β-Mg₁₇Al₁₂ are refined and chinese script type Mg₂Si phases are broken to dispersed particles after ECAP. The mechanical properties of the alloy after ECAP are significantly improved. After 4 passes of ECAP, the yield strength is increased from 50MPa to 109 MPa, tensile strength from 129MPa to 237MPa, elongation from 6% to 22%, and hardness from 61.2HBS to71.5HBS. The modification mechanism for microstructure and mechanical properties of the experimental alloy by ECAP was analyzed.

Abstract: In this study, Cu-Cr-Zr alloy joints are successfully fabricated by friction stir welding (FSW). Defect-free weld are produced on 12mm thick Cu-Cr-Zr alloy plate useing a non-consumable tool with a specially designed and shoulder with a constant rotation speed and a fixed traverse speed. The effect of friction stir welding (FSW) on the microstructure and mechanical properties of Cu-Cr-Zr alloy joints are investigated in details: The joints showed the presence of various zones such as nugget zone (NZ) and thermo-mechanically affected zone (TMAZ) and base metal (BM), the microhardness and the tensile strength of welded joints are lower than that of the base material.

Abstract: The Al-TiC and Al-TiAl₃ master alloys were prepared by thermal explosion method of aluminum melt, and the precipitation phenomenon of TiC and TiAl₃ particles were studied in aluminum melt through separate addition of Al-TiC master alloy and composite addition of Al-TiC and Al-TiAl₃ master alloys into aluminum melt. The results show that: When TiC exists in the aluminum melt separately, its speed of sedimentation is fast, and after a shorter time of heat preservation, a large amount of TiC will precipitate; when TiC and TiAl₃ coexist in the aluminum melt, the speed of precipitation will become slow, and after a longer time of heat preservation, only a small amount of TiC will precipitate; and before TiAl₃ settles to the bottom of the sample, it will dissolve. The attenuation of the refining effect of Al-TiC and Al-TiAl₃ is mainly caused by the precipitation of TiC and the dissolution of TiAl₃.

Abstract: Although alloy QCr0.5 has been used as the contact materials in the high-voltage equipment extensively, but it always confronts the awkwardness of over aging in the heat treatment, and results in brittleness during the switching on and breaking process. In the present work by the technology of interalloy-adding, the Zr-containing alloy Cu-0.8Cr-0.2Zr has been prepared and investigated. The results of the microstructure and properties indicate that the alloy matrix maintains FCC microstructure and lots of Zr-containing precipitation is dispersed in the matrix uniformly. The brinell hardness, the ultimate tensile strength and the elastic modulus increase greatly, reach 140 MPa, 430 Mpa and 130 GPa respectively, meanwhile the electric conductivity maintains 75%IACS and the softening temperature is up to 550 °C.

Abstract: In this study, the microstructures and mechanical properties of the recently developed Eco-2024-T3 alloy were examined. Eco-2024 is made using Eco-Mg (Mg-Al₂Ca) in place of element Mg during the manufacture of alloy 2024-T3. This is an alloy that has economic advantage and excellent properties. Alloy Eco-2024 showed smaller crystal grains that were distributed more evenly compared to the existing alloy 2024-T3. It consisted of Al matrices containing minute amounts of Al₂CuMg, Al₂Cu, and Ca phases and showed microstructures with reduced amounts of Fe phases or oxide. As a result of tensile tests, this alloy exhibited yield strength of 413 MPa, tensile strength of 527 MPa, and elongation of 15.4%. In other words, it showed higher strength than the existing alloy 2024 but was similar to the existing alloy 2024 in terms of elongation. In fatigue tests, alloy Eco-2024-T3 recorded fatigue limit of 330 MPa or around 80% of its yield strength; this is a much more excellent property compared to the existing alloy 2024-T3, which has fatigue limit of 250 MPa. Based on the aforementioned results, the correlation between the excellent mechanical properties of alloy Eco-2024-T3 and its microstructure was examined.