Material Properties and Classification
SUMMARY OF MATERIALS
Material Properties
We define the characteristics of the reactions to external actions that tend to alter the balance. In the first case, we have the intrinsic properties of the material, such as specific gravity, volume, crystallographic configuration, etc. In the event that the properties are manifest, an external cause acting in the material, this event can occur in two ways: either rely exclusively on the condition of the material is constant in it, and without the influential intensity agent, as in thermal or electrical conductivity, or to influence the material and the agent, such as strength and durability.
1. Organoleptic Properties
These are those concerning the appearance, color, size, and other circumstances that may be assessed by the simple exercise of the senses or with the aid of simple tools.
2. Physical Properties
These are those that relate to the actions of physical agents, such as weight, volume, specific gravity, etc. Worthy properties that relate to the body’s resilience to strength are of great importance in the construction industry.
3. Chemical Properties
Dependent on the intimate composition of the material, these refer to their reaction with their environment, gaining great importance in some materials’ resistance to corrosion.
2.2 – Organoleptic Properties
A. Appearance
Its shape, its dimensions, and its imperfections.
B. Color
C. Fracture
By breaking a material, it can be seen that it is divided into two pieces, which gives us a basic idea of uniformity and cohesion. The appearance of the fracture and its borders is closely linked to the structure of the material and its homogeneity. This fracture may be flat, chipped, undulating, leafy, etc.
D. Uniformity
A material is said to have a homogeneous constitution when it is uniform throughout its mass and can usually be assessed by simple observation.
- Cracks or hairline fractures, or very small cracks, can be filled with a softer material than the rest.
- Voids or cavities, including air-filled masses of soft material.
- Nodules or grains, harder material embedded in the mass.
2.3 – Physical Properties
A. Structure
Due to the different processes of manufacturing or processing, there is a different sort of molecules, producing management structures that are also different, which is often seen with the naked eye, while in other cases, you must use a microscope.
B. Density
Density is defined as the mass contained in a unit volume of a body. If we denote the density with the letter d, the density is given by:
- If the body is completely homogeneous, the ratio of body mass m and volume v that it occupies.
- And in the case of a body that is not homogeneous, the average density is calculated by taking progressively reduced volumes, reaching the limit of the concept of point density.
C. Specific Gravity
The ratio between the weight of the material and the volume it occupies in space. When it comes to gases, it is necessary to set the pressure and temperature at which it is located. In the case of the liquid state, it is almost never a simple body but is made for at least two phases, one of which is formed by solid particles that form the body mass, and the other liquid or gas. Although very often, it happens that there are three states: a solid phase formed by the body’s particles, another liquid consisting of water, and a third in gaseous air or steam.
D. Porosity and Compactness
Porosity is defined as the ratio of the volume occupied by the pores of the body and the total volume bound. It may be considered absolute or relative, as pores may be accessible or only total porosity concepts. The concepts of porosity and compactness are important in the possibility of absorption of water and its amount and on the mechanical strength of the material.
E. Absorption and Permeability
Any porous material can fill every pore with a liquid if it is immersed or with water vapor if it is in a proper relative humidity atmosphere.
The moisture content of a material is expressed in percent with respect to dry material to constant weight, i.e., so severe that even the continuation of the drying does not reduce it more.
F. Thermal Properties
It is known that material properties change with temperature. In most cases, the mechanical and physical properties depend on the temperature at which the material is used or the temperature at which the material is subjected during its proceedings.
Heat Capacity
A solid material, when heated, undergoes an increase in temperature, which means that some energy has been absorbed. The heat capacity is a property that is indicative of the ability of a material to absorb heat from the surroundings.Thermal Expansion
Most solids expand when heated and contract when cooled. This is a material property that is indicative of the extent to which a material expands under heating temperature and has units reciprocal (ºC)-1 or (ºF)-1.Thermal Conductivity
Thermal conduction is the phenomenon by which heat is transported from a region of high temperature to a low temperature of a substance.
G. Electrical Properties
Electrical conductivity is the ease with which each material will allow electricity to pass through it. The electrical resistance is directly proportional to its length and inversely proportional to its section. Based on their conductivity, materials are classified as:
- Conductors: Made of metals and alloys.
- Semiconductors: Those that behave normally as insulation and, in some circumstances, cease to be.
- Insulators: Those through which it is impossible for electricity to pass, and among those that can stand out from other ceramic phases.
H. Mechanical Properties
Describe how the material supports applied forces, including forces of tension, compression, impact, cyclic fatigue, or forces at high temperatures. Then you mention are defined below:
- Toughness: The property of certain materials to withstand, without deforming or breaking, sudden efforts that apply to them.
- Flexibility: It consists of the ability of some materials to recover their shape and size when the effort that had given deformation ceases.
- Hardness: The resistance a material opposes penetration.
- Fragility: A material is brittle when it breaks easily by the action of a shock.
- Plasticity: The ability of some solid material to acquire permanent deformation under the action of an external force or pressure without rupture.
- Ductility: Considered a variant of plasticity, it is the property of certain metals to stretch in the form of fine wires.
- Malleability: Another variation of plasticity, it is the possibility of transforming some thin sheet metal.
The above mechanical properties are measured accurately by mechanical tests:
- Tensile Test: Provides a rough idea of the tenacity and elasticity of a material.
- Hardness Testing: Allows us to know the hardness of the material.
- Impact Testing: Allows us to know the fragility and tenacity of a material.
- Technology Testing: They show the characteristics of plasticity that a material has to carry out its forge, bending, stamping, etc.
I. Technical Features
Determines the ability of a metal to be formed into useful or usable pieces or parts. These are:
- Ductility: The ability of the metal to be warped or worked cold. It increases with tenacity and decreases with increasing hardness. The most ductile metals are gold, silver, copper, iron, lead, and aluminum.
- Fusibility: The property that allows for castings or casts.
- Fluidity: The ability of a molten metal to produce complete and flawless castings. For a metal to be castable, it must possess high fluidity to completely fill the mold. The fusible and castable metals are cast iron, bronze, brass, and light alloys.
- Solderability: The ability of a metal to weld with another identical one under pressure on both hot. Steels with low carbon content have this property.
- Hardening Tempering: It is the property of the metal to suffer changes in its crystal structure as a result of successive heating and cooling and thus their mechanical and technological properties. Steels are tempered easily due to the formation of a characteristic crystal structure called martensite.
- Ease of Machining: This is the property of a metal being able to have chip removal machining by a proper cutting tool. Gray iron and bronze are very machinable, with chips cut into flakes. Mild steel and light alloys, with high tenacity, produce long chips.
2.4 – Chemical Properties
Among the chemical properties, we can find, among others, the bonding forces: as regards the composition of the material and then the behavior of materials to external aggressive media, such as corrosion. The chemical properties of atoms of the elements depend mainly on the reactivity of their outermost electrons. The most stable and least reactive of all elements are the noble gases.
Corrosion can be defined as the slow deterioration of a material by the action of an external agent. In the deterioration of materials, we can distinguish two processes:
Direct oxidation results from the combination of metal atoms with those of the aggressive substance.
Electrochemical corrosion is caused by the presence of electrochemical cells in which the metal acts as the anode and therefore dissolves. This type of corrosion requires the presence of aqueous environments and, in general, means of electrolytic conductivity.