Score Resistance of SAE781 (Al-Si-Cd) Automotive Journal Bearing Alloy-A Metallographic Analysis

The excellent score resistance of the journal bearing alloy SAE 781 (A1-4Si-1Cd) is attributed to a thin, 5 µm, layer of the Si phase on the surface. The Si particles have typical cross-sectional areas in the range of 10 - 20 µm² and show a concentration enrichment of greater than 15 times over that of the nominal alloy composition. Scored bearing surfaces did not exhibit an enriched layer of Si.