Effect of microstructure on fatigue behaviour of cast Al–7Si–Mg alloy

Abstract

The fatigue behaviour of a cast Al -7Si -Mg alloy, conforming to A356, has been studied. Specimens of this material were tested in both the as cast condition and a solution treated and aged condition. It was observed that the size, number, and position of casting defects influenced the fatigue life very strongly. This marked effect nearly hides that of the heat treatment. Nevertheless, if the analysis is carried out considering only results obtained from sound specimens it is revealed that the heat treatment causes an improvement in the fatigue resistance of the alloy.MST/4595

Friction Stir Processing Technology: A Review

“…[24] heat treatment are widely used to refine the microstructure of cast Al-Si alloys, to enhance the mechanical properties of the castings. [73][74][75] However, none of these approaches can heal the casting porosity effectively and redistribute the Si particles uniformly into the aluminum matrix.…”

Influence of surface and internal casting defects on the fatigue behaviour of A357-T6 cast aluminium alloy

“…However, it is well known that HCF lives (10 5 < N f < 10 7 cycles) of cast components are severely reduced when casting defects (notably pores and oxides) are present at the free surface or subsurface [1][2][3][4][5][6][7][8][9][10][11][12][13]. These defects as stress raisers and can considerably reduce the crack incubation period depending on their type, size, position and morphology and the microstructural features of the surrounding material.…”

Effect of Friction Stir Processing on Microstructure and Tensile Properties of an Investment Cast Al-7Si-0.6Mg Alloy

“…[1][2][3][4] The tensile properties of cast Al-Si alloys, in particular ductility and toughness, are limited by three major microstructural features (i.e., porosity, Si particles, and primary aluminum dendrites). [5][6][7][8] Refinement of the cast microstructure is necessary to address these limitations.…”

“…[11] During thermal modification, the casting is held at the solution treatment temperature for a long time to spheroidize the eutectic Si particles. [8] The second group of techniques for refining cast Al-Si microstructure acts on the coarse primary aluminum phase through heat treatments. Heat treatment at 850 K (577°C) for 8 minutes caused considerable refinement of aluminum dendrites in a semisolid processed A356 alloy.…”

“…The first category changes the Si particle morphology through chemical or thermal modification techniques. [8][9][10] Chemical modification is done by adding small amounts of sodium, strontium, or antimony (also known as eutectic modifiers) to the melt. [9,10] These elements change the shape of coarse acicular eutectic Si particles, making them fine globules.…”