Search

Aluminum alloys 5083, 6061, and 7075 are prone to hot tearing under direct-chill casting conditions; the defects that form during solidification of those alloys are highly sensitive to variation in the alloying elements, with these elements commonly being Si, Fe, Cu, and Ti. This study investigates the influence of the morphology, content, and size of intermetallic compounds on the hot tearing behavior of the 5083, 6061, and 7075 aluminum alloys by combining a constrained rod casting technique, phase diagram calculation, and multiscale microstructural characterizations. The fishbone-shaped α-Al15(Fe,Mn)3Si2 in 5083 can serve as a path for crack nucleation and growth, and an increase in Si content results in Mg2Si assuming fishbone morphology, thereby increasing hot tearing susceptibility. The amount of plate-like β-Al5FeSi is the primary factor controlling the hot tearing susceptibility of 6061. For 7075, increasing the Cu content can greatly enhance the remaining liquid fraction, feeding, and hot tearing susceptibility. For all three alloys, TiB2 grain refiner minimizes hot tearing. This study elucidates the influences of the amounts of Fe, Si, Cu, and TiB2 grain refiner on hot tearing susceptibility. The findings can help establish compositional control standards for the 5083, 6061, and 7075 aluminum alloy series, particularly when the recycling rate must be increased. [ABSTRACT FROM AUTHOR]

This paper presents an adaptive-speed/CAV algorithm which regulates the disc velocity in a CD-ROM system to accomplish high data throughput (bit rate) during continuous playback and low power consumption during continuous data access. The adaptive-speed profile is based upon quasi-CLV control [1] which allows drive optimization towards both data throughput and access time. The presented algorithm can automatically distinguish between two operating modes - continuous access and continuous playback. By detecting the state of continuous access, the CD-ROM drive switches its spindle-motor loop into a constant angular velocity (CAV) mode, avoiding therefore the acceleration/braking of the motor, and thus reducing the power consumption. By detecting the state of continuous playback, the spindle motor will be set to follow an adaptive-speed profile which is highly optimized for data transfer rate. The software and hardware implementation of the CAV/quasi-CLV switching technique in a CD-ROM system is also described. Keywords - access time, adaptive-speed CD-ROM drive, bit rate, CAV control, CD-ROM, CLV control, data throughput, quasi-CLV control, seek time.