Decreasing Aging Temperature Research Articles

1085. Measurements of dislocation pinning and dislocation damping in cold-worked copper at 1 Hz: G Sokolowski et al,Phys Stat Sol (a), 19 (2), 1973, 493–504

The aging response of various Al–Zn–Mg–Cu alloys was compared with the reinforced counterpart. The effects of aging temperature and time on the mechanical properties of these alloys, was also determined. Moreover, the effects of quenching rate from solution temperature, time between quench and aging, and heating rate to precipitation temperature were investigated. The study was executed by selecting two different heat treatments for each of three different aging temperatures: one without prior straining, and the other with 2% straining prior to aging to relieve stress. Room temperature tensile testing was conducted to determine these variations of aging on the strength of the spray formed Al–Zn–Mg–Cu alloys. The presence of SiC particles accelerated the aging kinetics of the alloys compared to the unreinforced counterparts. This difference in time to peak aging decreased with decreasing aging temperature. At uniform temperatures, differences for time to peak aging between unreinforced and composite alloys also existed in both the prestrained and unstrained condition. The difference was not as great in the prestrained state. The tensile strengths increased slightly with prestraining, but not significantly. Alloys containing silver maintained high strengths over silver-free counterparts when rapidly heated to precipitation temperatures above 120 °C. At slow heating rates, however, the silver-free alloys matched or were slightly higher than the strength of silver alloys, with increasing heating rate.

Light scattering and x‐ray characterization of amylose films

AbstractSmall‐angle light scattering (SALS) in the solid state and x‐ray diffraction were used to investigate the development of anisotropic structure in water‐cast amylose films prepared under various conditions. The conditions investigated were different temperatures and relative humidities maintained during the drying of the films and different aging times and temperatures of the amylose solution prior to the casting of films. As revealed by SALS, the predominant morphology developing in these films was based on rod‐like scattering units of considerable size. At times, a low degree of spherulitic character was also evident in the films. All four experimental conditions affected the development of anisotropic structure, with the aging time and temperature producing the most noticeable effects. Increasing aging time and/or decreasing aging temperature markedly increased the rod‐like morphology of the films. On the other hand, crystallite sizes as measured by x‐ray diffraction remained constant at 24–28 Å, indicating no influence on the part of experimental conditions. These findings are discussed in the light of starch retrogradation.