Skip to main content

Types Of Alloys And Compounds

 After solidification the alloying elements may exist in the base metal atoms in three general ways ,

1. Alloying Atoms may be relatively soluble in the base metal atoms forming a solid solution.

2. Alloying atoms may form a compound with the base metal atoms producing an intermetallic compound.

3. Alloying atoms may be relatively insoluble in the base metal atoms forming a mechanical mixture.




SOLID SOLUTIONS :

When elements combine to form alloys by completely dissolving in each other they are said to be in solid solutions. In a Solid solution, the different types of atoms of the components in the alloys by completely dissolving in each other they are said to be in solid solutions. In a solid solution, the different types of atoms of the components in the alloy form a common crystal lattice. The component, whose lattice is retained, is called solvent.

Conditions under which metallic solid solutions are formed are : 

(a) the components have the same crystal lattice and 

(b) There is no large difference in the lattice form of the alloying components.

The two most typical kinds of solid solutions are substitutional and interstitial.

In substitutional solid solutions, a part of atoms at the points of the solvent crystal lattice has been replaced by solute atoms.

In Interstitial solid solutions, the atoms of the solute metal occupy the vacant positions or interstices between the atoms of the solvent.

The nature of the solid solutions has important effects on many alloy properties. For example, strength and hardness increase with the amount of solute present , but ductility usually decreases. 

Intermetallic compounds, Compounds are obtained upon chemical interaction of  certain compounds of alloys. They are commonly formed between metals and non metals. Chemical compounds in the alloy not only have a definite chemical composition but also possess distinct physical and mechanical properties.

In an intermetallic compounds, the lattice form is the characteristic of the compound. It differs from those of its components, and usually is more complex. The lower order of symmetry in the complex lattices results in low electrical conductivity, and greater resistance to slip. Consequently , such compounds are very hard and brittle. To be of real value , they must be well dispersed through the structure. The softer base metal will then strengthen the latter.

Mechanical Mixtures, In some cases when a liquid solution is cooled, crystals of all components separate simultaneously from the melt and form a close mechanical mixture. This is also known as eutectic mixture. In mechanical mixtures, metals retain their same structural identity and properties. 

Labels:

Comments

Post a Comment

Popular posts from this blog

Advantages And Disadvantages Of Air Refrigeration System :

 Advantages Of  Air Refrigeration : 1. The refrigerant used namely air is cheap and easily available. 2. There is no danger of fire or toxic effects due to leakages. 3. The weight to ton of refrigeration ratio is less as compared to other systems. Disadvantages Of Air Refrigeration : 1. The quantity of  Refrigerant used per ton of refrigeration is high as compared to other systems. 2. The COP of the system is very low. Therefore running cost is high. 3. The danger of frosting at the expander valves is more as the air contains moisture content. 
Post a Comment
Read more

MELTING FURNACES FOR FERROUS METALS : CUPOLA AND ITS WORKING

Various types of melting furnaces are used in different foundry shops, depending upon the quantity of metal to be melted at a time, and the nature of work that is carried out in the shop.  The primary objective in cupola is to produce iron of desired composition, temperature and properties at the required rate in the most economical manner. Besides, this furnace has many distinct advantages over the other types, e.g., simplicity of operation, continuity of production, and increased output coupled with a high degree of efficiency.  Description Of a Cupola : The Cupola Furnace consists of a vertical, cylindrical steel sheet, 6 to 12 mm thick, and lined inside with acid refractory bricks or acid tamping clay. The refractory bricks or the tamping clay used consist of  silicon oxide acid (SiO2) and alumina (Al2O3). The lining is generally thicker in the lower where the temperatures encountered are higher than in the upper region. The shell is mounted either on a brick work fo...
Post a Comment
Read more

SIMPLE CARBURETOR - CONSTRUCTION AND WORKING

CONSTRUCTION OF SIMPLE CARBURETOR :  The main Components of Simple Carburetor are : Float Chamber, float, nozzle, venturi, throttle valve, inlet valve, and metering jet . In the float chamber, a constant level of petrol is maintained by the float and a needle valve.  The float chamber is ventilated to atmosphere.  This is used to maintain atmospheric pressure inside the chamber. The float which is normally a metallic hollow cylinder rises and closes the inlet valve as the fuel level in the float chamber increases to certain level. The mixing chamber contains venturi, nozzle and throttle valve. The venturi tube is fitted with the inlet  manifold. This tube has a narrow opening called venturi. A nozzle is provided just below the centre of this venturi. The nozzle keeps the same level of petrol as that of the level in the float chamber. The mixing chamber has two butterfly valves.  One is to allow air into the mixing chamber known as choke valve. The other is to al...
Post a Comment
Read more