Papers by Keyword: High Strength Alloys

Abstract: High strength aluminium alloys extrusions have successfully been applied for years in transportation industry. High strength alloys are normally understood to be alloys based on the Al-Mg-Zn system (7xxx) with addition of Cu in some cases and of course some micro structural controlling elements as Cr or Zr. The level of strength in the hardened condition (T6) is typical in the range from 320 to 500 MPa. The combination of strength and ductility of extrusions from the 7xxx series alloy gives several advantages in light weight construction and can contribute to lighter body and chassis in automotive. Significant improvements in extrusion speed are realized when the ratio Zn/Mg is increasing this means that alloys with high Zn and low Mg like 7108 and 7003 are favourable. Zr is the most promising element with respect to control the recrystallization phenomena. The fully understanding chemistry and the thermo-mechanical process route in profile based components manufacturing is concluded to be fundamental for high performance products.

Abstract: This paper studies the effects of sheet thickness on the forming limits of high strength aluminum alloys commonly used in the aircraft industry. The selected materials are 2024-T3 and 7075-T6 representing 2000 and 7000 series aluminum alloys. Two sets of experiments are carried out to identify the effects of sheet thickness on the forming behavior of the selected alloys. The first set of the experiments is tensile testing. The tensile properties of sheets with different thickness and different materials including the plasticity parameters are determined in the first set of experiments. The second set of the experiments is air bending. The minimum bending radius of the different series of materials is determined in the second set of experiments. The results of the tensile testing and air bending are studied both separately and in comparison with each other to identify the trends and to understand the mechanisms governing the observed trends. It is shown that the behavior of the studied alloys is to some extent different from the behavior of more ductile aluminum alloys and mild steels.

Abstract: In Mg-Al-Zn and Mg-Al-Mn alloys containing 2.0~6.0mass%Al and 0~1.5mass%Zn, grain refinement in the as-rolled (F) specimens containing large amount of Al and Zn are achieved by both dynamic recrystallization and dynamic precipitation during hot rolling and leads to high strength and high ductility at room temperature. At high temperatures, the tensile strength of the investigated alloys is almost the same, while the elongation of the F-specimens increases with increasing Al and Zn contents, leading to 150% in Mg-4.5%Al-1.5%Zn alloy. High Al and Zn contents alloys significantly accumulate large working strain in grain interiors, and involve large amounts of high angle grain boundaries and fine spherical precipitates, which can become the nucleation sites for recrystallization. Therefore, dynamic recrystallization in such alloys occurs at small strain region during tensile test. This dynamic recrystallization causes reduction of flow stress and large elongation by grain boundary sliding at high temperatures. Furthermore, .fine recrystallized grains contributes to deformation in normal direction, resulting in isotropic deformation behavior. Authors attempt to improve proof stress and its anisotropic property of Mg-Al-Zn wrought alloys by grain size and precipitates controls utilizing dynamic recrystallization and dynamic precipitation during hot extrusion. In the alloy specimens extruded at lower temperatures increasing Al and Zn contents enhance dynamic recrystallization and dynamic precipitation, resulting in grain refinement and large amount of Mg17Al12 precipitates. As a result, the extruded Mg-9%Al-1%Zn alloy specimen shows high tensile strength of 370MPa, 0.2% tensile proof stress of 240MPa and moderate elongation of 20%, which are almost same as standard values of tensile properties of T5-treated 6N01 Al extruded alloy. Furthermore, a ratio of compressive proof stress to tensile proof stress of the as-extruded specimen improves up to a higher ratio of 0.9 than that of Mg-3%Al-1%Zn alloy specimen with no precipitation, 0.5, due to prevention of tensile twin, which easily occurs during compressive deformation even under a low applied stress perpendicular to the extrusion direction, by dynamic precipitation of Mg17Al12 phase.

Abstract: 35CrMnSiA, is a kind of important engineering materials that used widely in modern manufacturing fields. The machinability of 35CrMnSiA Steel with hardness of HRc40±2 in high speed turning process was studied in this paper. It is concluded that, when high speed turning of this ultra-high strength alloy steel, the chief wear mode of ceramics is the crater on rake faces; the interaction of depth of cut and feed rate is one of statistic significant effects on cutting force; the interaction of cutting velocity of cut and feed rate is one of statistic significant effects on surface roughness Ra; besides, the empirical formula of average cutting temperature, cutting forces, surface roughness Ra, was established.

Abstract: In the current four-year term project in Japan, new platform science and technology is proposed as a core concept of research and development of advanced magnesium alloys together with understanding of their intrinsic characteristics. The research fields related to advanced super-light magnesium alloys for 21st Century have been focused to the selected three categories; ecomaterial design and processing, high qualification of mechanical performance, and high performance design and processing in functionality. On the basis of the obtained results, platform science and technology for environmentally benign and high performance magnesium alloys is constructed as an industrial base material for the next generation. As a result, numerous large-scale joint research and development projects on magnesium alloys based on partnerships between industries, academia and government has already started towards practical utilization since last year.