SPRAY FORMING AND CHARACTERIZATION OF AI-Si-Pb ALLOYS

Abstract

In the present study, investigations have been carried out on the effect of lead on the structure, mechanical properties and wear behavior of Al-Si-Pb alloys made by spray forming technique. These alloys are widely used in automotive and aerospace applications. The Al-Si-Pb spray forms are manufactured in the laboratory. The Si content is kept 6% and the Pb content is varied from 10% to 25% and rest is Al. The spray forms are tested for hardness, ductility (%El), tensile strength (UTS) and wear properties. The spray formed alloys were studied by using optical microscope to identify the different constituents and their distribution such as Si and Pb etc, which segregate along the grain boundaries during rapid solidification. The mechanisms of solidification have been investigated using Scanning Electron Microscope (SEM) and EDAX. The microstructural aspects are also observed to affect the wear behavior significantly. Higher Pb content is better suited for high wear resistance. Lead is present as second-phase particles in the matrix alloy and acts as a solid lubricant at the time of seizure. Seizure is avoided because frictional heating may cause local softening of the lead film where metals are momentarily in contact during sliding, and thus provide effective boundary lubrication. It is observed that the wear behavior is affected by various mechanical properties. The wear behavior is also dependent on ultimate tensile strength, as the ultimate tensile strength increases the weight loss also increases.