**4. Mechanical testing and materials characterizations**

Whether a material is suitable for a given application is specified by the material properties. These properties can be measured using a series of mechanical tests, such as tensile, compressive, hardness and fatigue testing (**Figure 2**) as well as physical and chemical tests. Some of the mechanical tests are easily accessible like hardness. Others are difficult to measure such as tensile or yield strength where special samples must be formed. It is difficult to determine other properties such as fatigue, toughness strength as the tests need several

**Figure 2.** *Commonly used mechanical testing techniques.*

samples per every case and the testing process takes a long time. Apart from the above tests, it is also possible to predict the properties of materials by determining the microscopic structure of materials, where properties are determined by the microstructure. There are a number of microstructural characterization techniques including optical microscopy, scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), X-ray diffraction (XRD), transmission electron microscopy (TEM), ultrasonic sound based methods and magnetic-based methods [15]. Among these techniques, optical microscopy and electron microscopy are able to detect the morphology of microstructural features in the surface of a prepared sample. Optical microscopy has its own advantages such as low cost, ease of use on large sample areas and ease of operation. However, electron microscopy is also widely used due to its high resolution down to the nanometer scale [16].

The factors that often determine the properties of strength and toughness of pearlitic steels like interlamellar spacing, colony size, and prior austenite size can be done by examining the microstructure of these materials [17, 18]. However, measuring the size of the colony and especially the size of the prior-austenite grains is extremely difficult and requires a proficient technical examination using optical microscopy or SEM and special procedures. For multiple phases of steels, the fraction, morphology, size and distribution of the phase components are determined by the properties. XRD is an effective technique for measuring the fraction of the present phases, but cannot access the size, morphology and distribution. Image analysis techniques are also applied for this application. Unlike the XRD analysis, which is a crystallographic analysis of the bulk surface, image analysis technique extracts information directly from a microscopic image of the sample surface. So once the current features in the sample images are categorized into phases, the size, fraction, morphology and phase's distribution can easily be obtained. Most of the current image analysis-based characterization uses the histogram of the brightness (intensity) of the individual pixels that make up the image, and relies on all the pixels in one phase having intensities in a

**5**

ties (**Figure 3**).

**Figure 3.**

**5. Steel metallurgy**

automotive industry [22].

*Introductory Chapter: A Brief Introduction to Engineering Materials and Metallurgy*

different range from all of those in another phase [19]. This makes it very easy to distinguish between the phases only using the threshold, and it has been shown to work with some two-phase steels characterized by high variability between phases [20]. However, the different phases in brightness levels overlap for many other steels with complex microscopic structures. In this case, the threshold of intensity is no longer able to distinguish between the phases, and instead some analysis of the spatial patterns of intensity within the phases, i.e., "texture," is required. Quantitative analysis of microstructural images allows not only a quality control examination of the treatment path, but also the possibility of establishing a reciprocal relationship between microstructure features and associated proper-

*Microstructure related with fabrication of components and their properties.*

Steel has been one of the most important materials used by humans for up to 4000 years due to its good combination of low cost and properties. The mechanical properties of steel have been found to be highly dependent on its internal structure at nanometers up to microns or even millimeters (its "microstructure"). The internal structure of the steel can be adjusted through composition changes, mechanical deformation or heat treatments. The metal can then be designed to meet the different requirements in a range of applications. Atoms can be arranged into steel and bonded, called phases in several ways. Different phases have various properties, which may be suitable for various applications, either singly or in groups. For example, high-strength steels have good wear and abrasion resistance as well as high tensile strength, so they are widely used as rail steels and steel wire [21]. Steel with more than one phase including two-phase steels, complex steels and transformation induced plasticity steels usually has a good mix of toughness and strength and is therefore well suited for applications that require strength and formability as in the

*DOI: http://dx.doi.org/10.5772/intechopen.86497*

*Introductory Chapter: A Brief Introduction to Engineering Materials and Metallurgy DOI: http://dx.doi.org/10.5772/intechopen.86497*

#### **Figure 3.**

*Recent Advancements in the Metallurgical Engineering and Electrodeposition*

samples per every case and the testing process takes a long time. Apart from the above tests, it is also possible to predict the properties of materials by determining the microscopic structure of materials, where properties are determined by the microstructure. There are a number of microstructural characterization techniques including optical microscopy, scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), X-ray diffraction (XRD), transmission electron microscopy (TEM), ultrasonic sound based methods and magnetic-based methods [15]. Among these techniques, optical microscopy and electron microscopy are able to detect the morphology of microstructural features in the surface of a prepared sample. Optical microscopy has its own advantages such as low cost, ease of use on large sample areas and ease of operation. However, electron microscopy is also widely used due to its high resolution

The factors that often determine the properties of strength and toughness of pearlitic steels like interlamellar spacing, colony size, and prior austenite size can be done by examining the microstructure of these materials [17, 18]. However, measuring the size of the colony and especially the size of the prior-austenite grains is extremely difficult and requires a proficient technical examination using optical microscopy or SEM and special procedures. For multiple phases of steels, the fraction, morphology, size and distribution of the phase components are determined by the properties. XRD is an effective technique for measuring the fraction of the present phases, but cannot access the size, morphology and distribution. Image analysis techniques are also applied for this application. Unlike the XRD analysis, which is a crystallographic analysis of the bulk surface, image analysis technique extracts information directly from a microscopic image of the sample surface. So once the current features in the sample images are categorized into phases, the size, fraction, morphology and phase's distribution can easily be obtained. Most of the current image analysis-based characterization uses the histogram of the brightness (intensity) of the individual pixels that make up the image, and relies on all the pixels in one phase having intensities in a

**4**

**Figure 2.**

down to the nanometer scale [16].

*Commonly used mechanical testing techniques.*

*Microstructure related with fabrication of components and their properties.*

different range from all of those in another phase [19]. This makes it very easy to distinguish between the phases only using the threshold, and it has been shown to work with some two-phase steels characterized by high variability between phases [20]. However, the different phases in brightness levels overlap for many other steels with complex microscopic structures. In this case, the threshold of intensity is no longer able to distinguish between the phases, and instead some analysis of the spatial patterns of intensity within the phases, i.e., "texture," is required. Quantitative analysis of microstructural images allows not only a quality control examination of the treatment path, but also the possibility of establishing a reciprocal relationship between microstructure features and associated properties (**Figure 3**).

### **5. Steel metallurgy**

Steel has been one of the most important materials used by humans for up to 4000 years due to its good combination of low cost and properties. The mechanical properties of steel have been found to be highly dependent on its internal structure at nanometers up to microns or even millimeters (its "microstructure"). The internal structure of the steel can be adjusted through composition changes, mechanical deformation or heat treatments. The metal can then be designed to meet the different requirements in a range of applications. Atoms can be arranged into steel and bonded, called phases in several ways. Different phases have various properties, which may be suitable for various applications, either singly or in groups. For example, high-strength steels have good wear and abrasion resistance as well as high tensile strength, so they are widely used as rail steels and steel wire [21]. Steel with more than one phase including two-phase steels, complex steels and transformation induced plasticity steels usually has a good mix of toughness and strength and is therefore well suited for applications that require strength and formability as in the automotive industry [22].
