The following points highlight the four main types of binary diagrams. The types are: 1. Solid Solution Systems 2. Insoluble in the Solid State 3. Soluble in the Solid State 4. Peritectic Reaction. Binary phase diagrams are based on two component systems. Here, the two components may be mixed in an infinite number of different proportions, that is, composition also [...]
Various types of point defects are: 1. Vacancy 2. Interstitialcy 3. Frenkel Defect 4. Impurity Atoms. A point defect is a very localised disruption in the regularity of a lattice. It is a defect of dimensions just like a point (zero dimensions). The size of the defect could be one atom, or two atomic diameters, which is just like a [...]
In this article we will discuss about:- 1. Introduction to Solidification 2. Structure of Crystalline Solid 3. Energetics 4. Smooth or Stable Interface-Growth 5. Temperature Inversion and Dendritic Growth 6. Dendritic Growth. Introduction to Solidification: A metallurgist is called upon to economically produce the required shape of an object, and which has the required properties. In almost all metals and [...]
The following points highlight the three main surface defects in crystals. The types are: 1. Free Surfaces 2. Grain Boundaries 3. Stacking Faults. Surface defects are defects of two dimensional nature in the mathematical sense (that is, they have two dimensions). These are areas of distortions that lie about a surface, having a thickness of a few atomic diameters (that [...]
Pores, voids and blow holes are defects in solid castings. Voids can be regarded as an agglomeration of vacancies. Pores are discontinuities or holes in solid parts. Such defects normally form during freezing due to one or combination of both the factors: (i) Evolution of dissolved gas at the solid-liquid interface. (ii) Decrease in volume that occurs during freezing in [...]
In this article we will discuss about the process of nucleation and growth of liquid metals. Suppose the temperature of the liquid metal is brought below its freezing temperature, so that solid metal x is now a stable phase. How does the solid appear, and the liquid disappear? It would be unrealistic to assume that such a change occurs all [...]
All solids get deformed, i.e., show change in shape if an external load is applied on them. The basic types of deformations could be broadly divided into two categories: 1. Time-Independent Deformation: (i) The time independent deformation, which disappears (i.e., object returns to its original shape) on the release of load is called elastic deformation. Thus, elastic deformation is a [...]
In this article we will discuss about the atomic approach to elastic deformation of metals. At absolute zero, the two neighbouring atoms in a metal are in stable equilibrium state when the distance between them is r0. Fig. 6.11 illustrates this schematically. At large distance of separation between two atoms, the main force is of attractive nature, FA (negative). When [...]
In this article we will discuss about the plastic deformation of metals with its diagram. Referring to Fig. 6.2 the deformation of the specimen is elastic up to the yield point (or elastic limit) and it becomes plastic, i.e. the linear elastic region is followed by a nonlinear plastic region. Although yield strength is an important design parameter for machine [...]
In this article we will discuss about:- 1. Introduction to Corrosion 2. Classification of Corrosion 3. Rate 4. Corrosion Rates from Polarisation and Mixed Potential Theory. Introduction to Corrosion: Corrosion is responsible for colossal loss of materials occurring everywhere every moment involving billions and billions of rupees annually. It is one of the most serious destructive agents, and is one [...]