What are the characteristic properties of alloys?

In general, alloys have been found to be stronger and harder, less malleable, less ductile, and more corrosion-resistant than the main metal making the alloy. An alloy mixture is stronger because it contains atoms from different elements that are different in sizes.

What is Al-Si?

Al-Si Cast Alloys – Microstructure and Mechanical Properties at Ambient and Elevated Temperature. ABSTRACT. Aluminium alloys with Si as the major alloying element form a class of material providing the most significant part of all casting manufactured materials.

Which element is added for modification of Al-Si alloy?

Binary aluminum–silicon alloys, however, have relatively low strengths. Hence, other elements such as copper and magnesium are added to obtain higher strengths through heat treatment. A small amount of sodium or strontium is frequently added to modify the aluminum–silicon eutectic to give increased ductility.

What are major characteristics of alloying element?

Characteristics of alloying elements Nickel (Ni) – increases strength, impact strength and toughness, impart corrosion resistance in combination with other elements. Chromium (Cr) – improves hardenability, strength and wear resistance, sharply increases corrosion resistance at high concentrations (> 12\%).

What are the properties and composition of alloys?

alloy, metallic substance composed of two or more elements, as either a compound or a solution. The components of alloys are ordinarily themselves metals, though carbon, a nonmetal, is an essential constituent of steel. Alloys are usually produced by melting the mixture of ingredients.

Which phases are present in eutectic Al-Si alloy?

This means that there is no beta phase and so this phase is “replaced” by pure silicon (you can think of it as a beta phase which consists only of silicon). So, for Al-Si alloys, the eutectic composition is a structure of alpha+Si rather than alpha+beta.

What is meant by modification of eutectic alloys?

The term ‘modification’ describes the change in scale and morphology of the eutectic Si from a coarse flake-like structure to a fibrous or fine flake structure in Al-Si alloys. It is necessary to modify the eutectic Al-Si to improve strength, ductility, pressure tightness and machinability [84] .

What is the main objective of the mechanical modification technique?

Modification reduces the size of eutectic Si particles to enhance the cast’s mechanical properties such as ductility and strength.

What is eutectic solidification in Al-Si?

Mode I eutectic solidification occurs in unmodified commercial Al-Si alloys, usually with a very high nucleation frequency. Addition of strontium promotes eutectic solidification according to Mode II, while sodium modification promotes Mode III eutectic solidification.

What is the binary Al-Si phase diagram?

The binary Al-Si phase diagram was initially studied by Fraenkel of Germany in 1908. It is a relatively simple binary diagram where there is very little solubility at room temperature for Si in Al and for Al in Si. Thus, the terminal solid solutions are nearly pure Al and Si under equilibrium conditions.

What is the melting point of Si and Al at different temperatures?

The melting points of Al and Si are, respectively, 660.45 and 1414 °C, while the eutectic reaction occurs at 12.6 wt. \% Si and 577 ± 1 °C2. The maximum solubility of Si in Al occurs at the eutectic temperature and is 1.65 wt. \%. At least up to the late 1950’s, the eutectic was believed to be at 11.6 wt. \% Si.

What is the density of aluminum alloys?

Aluminum alloys are second only to steels in use as structural metals. Aluminum has a density of only 2.7 g/cm3, approximately one-third as much as steel (7.83 g/cm3). One cubic foot of steel weighs about 490 lb; a cubic foot of aluminum, only about 170 lb.