Papers by Keyword: Sc Addition

Abstract: The changes in texture and microstructure that occur during superplastic deformation (SPD) of a suitably thermo-mechanically processed (TMP) Al alloy AA7010 containing Sc at a temperature and strain rate combination of 475°C, 1.9x10^-2s^-1 have been examined. It is observed that during the early stages of SPD, there is a significant increase in the Brass {110}<112> component as well as a considerable increase in the S {123}<634> component. Whilst, these components gradually decrease leading to the randomization of texture as the SPD process progresses to larger strains. These results are discussed in terms of the nature of the TMP together with significant variations in the number density of Al₃Sc_xZr_1-x dispersoids and percentage recrystallization with strain.

Abstract: In this study, the microstructure and the texture development in Al–Zn–Mg–Cu–Zr alloys with/without 0.1%Sc has been investigated after extrusion, cold rolling, and aging treatment. After aging treatment, in Al alloy without Sc recrystallized equiaxed grains are obtained, while in Al alloy with Sc fine grains with an average size of 0.1~0.3 μm are obtained. After cold rolling, in case of the sample from the cross section (CS) to which Sc was added, texture with {112}<111>(Cu) + weak {123}<634>(S) component was developed while in case of the sample from longitudinal section (LS) to which Sc was added, texture with strong β-fiber + {110}<001>(Goss) components was developed. In case of CS and LS without Sc, texture of β-fiber was developed. After solid solution treatment and aging treatment, Al alloys (LS and CS) with Sc had rolling texture while Al alloys without Sc had random texture. The role of these differently developed textures in the plastic behavior, such as the normal anisotropy r-value (the plastic strain ratio) and planar anisotropy
r-values are discussed.

Abstract: The influence of Sc addition on the high temperature compressive strength of a commercial alloy 7010 (hereafter termed base alloy) has been examined. The base alloy, and the base alloy with 0.23 wt% Sc were cast, homogenized and subjected to compression tests at temperatures ranging from 300 to 450oC and strain rates of 10-3, 10-2, 10-1 and 1 sec-1. It is shown that Sc addition to the base alloy increases the compressive flow stress under these deformation conditions. The increase in peak flow stress is nearly 3-6 times the peak flow stress of the base alloy at temperatures 300-350oC over the strain rate range investigated. Whilst, at temperatures ³ 400oC, the flow stresses decrease significantly irrespective of the strain rate used. Transmission electron microscopy (TEM) revealed that a combination of (1) increased nucleation frequency of dispersoids, (2) evolution of smaller subgrain size, and (3) refinement of alloy phases in the Al-Zn-Mg-Cu system contribute to superior strengthening in the alloy containing Sc. Whilst, it is primarily a combination of coarsening and instability of the alloy phases in the Al-Zn-Mg-Cu system that dramatically reduces the flow stresses in both the alloys at temperatures ³ 400oC.

Abstract: The commercial 7xxx series Al alloys are based on medium strength Al-Zn-Mg and high strength Al-Zn-Mg-Cu systems. The medium strength alloys are weldable, whilst the high strength alloys are nonweldable. On the other hand, the Cu-free, weldable alloys suffer from poor SCC resistance. It is the purpose of this article to provide quantitative data and microstructural analysis to demonstrate that small additions of either Ag or Sc to Al-Zn-Mg and Al-Zn-Mg-Cu alloys bring about very significant improvement in SCC resistance and weldability, respectively. The improvement in SCC resistance of the Cu-bearing alloys due to over aging and retrogression and reaging (RRA) is further discussed in light of a similar improvement in the SCC resistance of these alloys, when peak aged, due to Ag and Sc additions.

Abstract: It has been reported that scandium addition improved various properties of aluminum alloys. However, present authors can not find any reports about the addition of Sc to 6000 series alloys. In this study, Sc was added to 6061 alloy and various effects of the Sc addition on aging behavior were examined, comparing with Al-Sc binary alloy. In the STQ state, resistivity at 77K, ρD77, of 0.2%Sc added alloy (6061+Sc) was about 2.0n-m higher than the alloy of no addition (6061). The ρD77 increased in initial stage of isothermal aging up to 473K, then decreased. Though ρD77 of binary Al-0.176%Sc alloy began to decrease from 1.8Ms at 448K and 18ks at 523K, excess decrease in ρD77 of 6061+Sc corresponding to precipitation of Sc compounds was not clear. Peak value of the HV0.1 was decreased and peak aging time delayed by the Sc addition in aging up to 498K. However, softening by overaging was retarded by the Sc addition. These effects of the Sc addition are considered to come from vacancy trap by solute Sc atoms or interface between particles of Sc compound and matrix acting as vacancy sinks.

Abstract: After extrusion, cold rolling and T-6 treatment, microstructure, texture development, and deep drawability of Al-5.09%Zn-1.83%Mg-0.32%Cu-0.25%Mn-alloy with 0.1% Sc are studied. After T-6 treatment, recrystallized equiaxed grains with an average grain size of 1~2㎛ are obtained. During extrusion the very strong <111>-fiber + medium sharp <100>-fiber + weak <210>-fiber texture is developed, which influences the formation of rolling texture. The texture, after 80% cold rolling, can be described by the strong {112}<111>(Cu) + {123}<634>(S) component in the cross section of the extruded rod, the strong b-fiber + weak {110}<001>(Goss) components in the longitudinal section, and the strong {110}<112>(Bs) + weak {001}<100>(Cube) components in the transverse section. The types of rolling texture are not changed after the T-6 treatment, but the maximum density of ODF is higher. The calculated mean r-values, rm, and the planar anisotropy, Dr, are relatively high, which are dependent on the texture.