The present study examines the effect of trace additions copper (up to 1 wt.%) and zinc (0.5 as alloying elements on microstructure, hardness, wear behaviour T6 treated A356 (Al-7Si) alloy. Wear tests were conducted using a pin-on-disc tribometer under constant sliding speed 200 RPM, varying applied load (20–40 N), distance (0–3000 m) determine rate coefficient friction. results indicated minim...

To the Editor: A recent article in PNAS by Asikainen and Werle (1) reports on the occurrence and morphology of ferromanganese nodules found in a New Hampshire lake. The authors offer data on the shapes, banding, composition, and distribution of the nodules and crusts. They also state that my paper (2) claims that the morphology of such nodules is controlled by elemental concentrations and that ...