Relationships between microstructural and mechanical aging effects in eutectic PbSn and Pb-free solder alloy Sn3.9Ag0.6Cu are reported and compared. The room temperature aged Sn3.9Ag0.6Cu alloy continually age-softened, this softening correlated with the growth of relatively large tin-rich crystals. The 180°C aged Sn3.9Ag0.6Cu alloy initially age-softened, and the minimum flow strength was reached after one day at 180°C. This softening correlated with the growth of relatively large tin-rich crystals and with the coarsening of Ag3Sn particles. When aged at 180°C beyond one day the Sn3.9Ag0.6Cu alloy age-hardened, the hardening correlated with the dispersion of Ag3Sn particles into tin-rich crystals which previously had not contained intermetallic precipitates.
This article provides information about the actual and potential uses of interactive videõ n instruction i.n an effort to motivate educators to consider using this technology to tmprov.e teachmg. The authors (I ) describe the continuing evolution of computer-based educational tools;(2) examine instances when an interactive videodisc provides viable instructional solutions to otherwise very difficult or impossible tasks; (3) discuss several models for delivering instruction to accommodate different learning styles and teaching methods; and (4) provide a framework for designing lessons systematically based on proven methods.
The present paper presents cyclic strain amplitude and longitudinal strain measurements of longitudinally compressed Terfenol-D particle samples subjected to magneto-strain cycling. A comparison is made of the responses of material strain cycle tested at temperatures near the matrix glass transition start temperature, and material strain cycle tested at a temperature near the matrix glass transition finish temperature. The cyclic strain amplitude of the material was significantly larger when tested at a temperature near the matrix glass transition finish temperature. A useful range of longitudinal applied stress exists where the composite suffers little apparent degradation. Beyond this range the composite exhibits steadily decreasing cyclic strain amplitude with increases in longitudinal compressive stress magnitude.
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