An Experimental Study of the Solidification Thermal Parameters Influence upon Microstructure and Mechanical Properties of Al-Si-Cu Alloys

Mauricio Silva Nascimento,Antônio Augusto Couto,Antônio Tadeu Rogério Franco,Carlos Frajuca,Givanildo Alves Dos Santos,Francisco Yastami Nakamoto

doi:10.1590/1980-5373-mr-2017-0864

Abstract

Metals solidification involves the transformation of the molten metal back into the solid state. Solidification structures impact heavily on the final product's characteristics. The microstructure effects on metallic alloys properties have been highlighted in various studies and particularly the dendrite arm spacing influence upon the mechanical properties such as tensile strength has been reported. In the present investigation, Al-10wt%Si-2wt%Cu and Al-10wt%Si-5wt%Cu alloys were directionally solidified upward under transient heat flow conditions. The experimental results include solidification thermal parameters such as tip growth rate and cooling rate, optical microscopy, volume fraction of the eutectic mixture, primary dendritic arm spacing and ultimate tensile strength. Experimental growth laws of primary dendrite arm spacing as a function of the solidification thermal parameters are proposed. The Hall-Petch mathematical expressions were used to correlate the ultimate tensile strength as a function of the primary dendritic arm spacing. It was found that the alloy with higher copper content had a more refined structure. More refined structures had higher ultimate tensile strength values.

Highlights

The liquid transformation into a solid is probably the most important phase transformation in applications of science and engineering materials[1,2]
The microstructure effects on metallic alloys properties has been highlighted in various studies and the grain size influence and dendrite arm spacing upon the mechanical properties has been reported[1,4]
Costa et al[7] investigated the influence of silicon on the microstructure comparing directional upward and horizontal solidification for the alloys Al-6wt%Cu-4wt%Si and Al-6wt%Cu, demonstrating that silicon alloying contributes to significant refinement of primary/secondary dendrite arm spacings

Summary

Introduction

The liquid transformation into a solid is probably the most important phase transformation in applications of science and engineering materials[1,2]. The microstructure effects on metallic alloys properties has been highlighted in various studies and the grain size influence and dendrite arm spacing upon the mechanical properties has been reported[1,4]. The ternary system (Aluminum, Silicon and Copper) has excellent properties as mechanical strength, low density as compared to ferrous alloys and good flowability. These properties make the system a good choice on automotive and aerospace industry, calling researchers attention[3,6]. Costa et al[7] investigated the influence of silicon on the microstructure comparing directional upward and horizontal solidification for the alloys Al-6wt%Cu-4wt%Si and Al-6wt%Cu, demonstrating that silicon alloying contributes to significant refinement of primary/secondary dendrite arm spacings. Araujo et al[8] investigated the interrelation between the secondary dendrite arm spacing and microhardness for

Methods

Results

Conclusion