Comparison of dynamic mechanical properties of non-superheated and superheated A357 alloys

TL;DR

This study compares the microstructure and dynamic mechanical properties of non-superheated and superheated A357 alloys, revealing microstructural differences and their effects on properties like damping capacity and storage modulus.

Contribution

It provides new insights into how superheat treatment alters the microstructure and dynamic mechanical behavior of A357 alloys.

Findings

Superheated A357 has finer, rounded eutectic Si particles.

Superheated A357 exhibits higher damping capacity at elevated temperatures.

Both alloys show increased loss modulus with temperature.

Abstract

The influence of superheat treatment on the microstructure and dynamic mechanical properties of A357 alloys has been investigated. The study of microstructure was performed by the optical microscope. Dynamic mechanical properties (storage modulus, loss modulus, and damping capacity) were measured by the dynamic mechanical analyzer (DMA). Microstructure showed coarser and angular eutectic Si particles with larger {\alpha}-Al dendrites in the non-superheated A357 alloy. In contrast, finer and rounded eutectic Si particles together with smaller and preferred oriented {\alpha}-Al dendrites have been observed in the superheated A357 alloy. Dynamic mechanical properties showed an increasing trend of loss modulus and damping capacity meanwhile a decreasing trend of storage modulus at elevated temperatures for superheated and non-superheated A357 alloys. The high damping capacity of superheated A357 has been ascribed to the grain boundary damping at elevated temperatures.