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Advance High Strength Steel Conventional low carbon mild steel has simpler ferritic structure (α-iron) and good ductility. Common type of HSS is High Strength Low Alloy (HSLA) ⇥ has yield strength  550 - 690 N/sq.mm . Manganese ⇥ supporter (stabilizer) of ferrite. Conventional HSS : Is single-phase ferritic steel with a potential for some pearlite in C-Mn steel. Lower strain hardening capacity. Advance HSS : primarily steel with a microstructure containing a phase other than ferrite, pearlite, cementite. Higher strain hardening capacity. Case Study of Automobile There are three different zones in a car: Crumple Zone (Front & Back) Middle Compartment Safety Cage Some important points about these zones are: Crumple Zone   ⇥  Made with those materials which absorb maximum amount of energy. Safety Cage   ⇥  Multiple areas (like cabins, structural elements). Areas of Safety cage are described ahead: Cabins (Blue Areas)   ⇥  Should have high streng...

Nano-Materials  It is defined as, " materials having size of individual building blocks less than 100 nm " . Bulk gold   ↔  have no catalytic properties but Au-Nanocrystal   ↔  excellent low temperature catalyst. Why Nano-materials? At nanoscale strange things happen to materials and their properties may change. Reactivity   ↔  smaller particles react differently with their environment than larger particles. Size   ↔  have different optical and reflection properties. Magnetism   ↔  have different magnetic properties. Nanomaterials Synthesis Technique It includes design and preparation of nanomaterials with high functionality (i.e. to fabricate nanoparticles with suitable properties). Synthesis involves the control of size, shape, structure and composition and purity of constituents. Method of synthesis Growth Kinetics 1. Method of Synthesis Two approaches are used: a. Top-Down Approach Refers to slicing or cutting of bulk materials....

Corrosion Deteriorative Mechanisms In Metals   ↠  actual metal lost by corrosion (dissolution) or oxidation (formation of non-metallic scale or film). In Ceramic Materials   ↠  resistant to deterioration but occurs at elevated temperature. In Polymers (degradation)   ↠  may dissolve in liquid solvent or absorb solvent. Corrosion in Metals It is defined as, " the destructive or unintentional attack on a metal " .  5 % of income is spent on corrosion prevention and maintenance. Corrosion is occasionally used as advantage: Etching (chemical reactivity of grain boundaries). Current develops in dry cell batteries. Types of Corrosion Uniform Attack   ↠  form of electrochemical corrosion that occurs with equivalent intensity over the exposed surface and often leaves behind a deposit. Galvanic Corrosion   ↠  occurs when two metals or alloys having different compositions are electrically coupled while exposed to an electrolyte. Crevice C...

Ceramics It is defined as, " when two metal react with each other to form a compound not solid solution " . Inorganic material (between metallic & non-metallic materials) Firing or Burnt Stuff   ⇉  Desired properties of ceramics are achieved at very high temperature heat treatment process. Ceramic structure   ⇉  more complex structure than metals and has at least 2 elements . Characteristics of Ceramic Structure Exhibit combinations of ionic and covalent bond. Degree of ionic character depend on electronegativity. Influence on Ceramic Structure Magnitude of charge on each component (crystal should be neutral). Relative sizes of cation and anions ( cation radii < anion radii  i.e. r C /r A  < 1 ). Coordination Configuration  It is defined as, " Maximum number of neighboring touching center atoms " .  Stable Ceramic structure   ⇉  form when anions surrounding a cation are in contact. For a specific coordination number   ⇉...

Polymers " Very large molecules made when hundreds of monomers join together to form long chain " . Repeat Unit   ⇔  group of atoms that repeat itself in polymer chain. Used in automobiles, sports, toys, household items, etc. Advantages: Lightweight Strong and durable  Easy to manufacture Disadvantages: Don't easily biodegrade  End up producing large amount of waste Related Terms Saturated Hydrocarbons   ⇔  in which each carbon is singly bonded to four other atoms. Unsaturated Hydrocarbons   ⇔  in which double or triple bond between carbon atoms present. Isomerism   ⇔  Two compounds with same composition but have different atomic arrangements. Polymorphism   ⇔  Existence of more than one crystal structure of a material (like BCC, FCC iron). Monomer   ⇔  small and unreacted single molecule for a polymer. Mer   ⇔  reacted single repeat unit of a polymer. Polymer or Macro-Molecule   ⇔  A polymer ...

Components These are pure metals. Combination of components is called Alloy .  System   ↠  refers to specific body (region) of material under consideration. Solid Solution   ↠  Solute atoms occupy solvent atoms substitutional and interstitial spaces. Solubility Limit It is defined as, " Maximum concentration of solute atoms that may dissolve in solvent to form solid solution at specific temperature " . It depends on temperature. Phases It is defined as, " a homogenous portion of a system that has uniform physical and chemical characteristics " . Single-phase system  ↠  homogenous system . Two or more phase system  ↠  heterogenous system. Microstructure It is defined as, " a subject to direct microscopic observation using optical or electron microscopes " . Microstructure is characterized by number of phases present, their proportion and manner in which they are arranged . Microstructure of alloy depends on alloying elements, concentrations, h...

Failure of Engineering Materials Improper material selection  Material processing (impurities, defects) Inadequate design of components Misuse  Failure (or fracture) in materials is of 2 types: Ductile Fracture   ⇔  accompanied by significant plastic deformation , showing necking behavior . Brittle Fracture   ⇔  little (or no) plastic deformation, catastrophic (or instantaneous) failure. Classification of Failure Failure is further divided into following types depending on percentage elongation ( %EL ). Very Ductile   ⇔  if  %EL > 20%,  which can be converted into wires (like gold, etc.) Moderately Ductile   ⇔  if   20% < %EL < 5%,  almost all metals. Brittle   ⇔  if  %EL < 5% , flat deformation. Failure is further divided into following depending on crack propagation . Trans-Granular Fracture   ⇔  If crack propagates within the grains . If plane is weak, crack propagates ...

Diffusion  It is defined as, " The transportation of one atom from one state into other state " . Used for hardening of surfaces like die parts, gear, bolt, machine element. Hardening can be done using Temperature-Heat treatment ( diffusion couple ). There are two types of diffusion: Inter-diffusion   ↔ in which atoms tend to migrate from region of high concentration to low concentration . Self-diffusion   ↔  in which atoms migrate within a solid. Diffusion Mechanism There can be two conditions of moving atoms Empty spaces between adjacent sites. Atoms have sufficient energy to break bond with neighbors atoms which cause lattice distortion during displacement. If we rise temperature, small fractions of atoms is capable of diffusive motion (which cause lattice distortion). Types of Diffusion 1. Vacancy Diffusion It is defined as, " interchange of an atom from a normal lattice position to the adjacent vacant lattice site " . Extent of vacancy diffusion is a function...

Microscopic Techniques It is defined as, " techniques used to examine structural elements and defects in crystalline materials " . Microstructure   ↠  combination of crystal structure + grain size + defects in crystal structure + phase + impurities . Microscopy   ↠  used for the investigation of microstructural features (instruments). Applications of microscopy and micro-structure are: Ensure association between the properties, structures and defects. To predict property of material (after relationship created). To design alloys with new property combination. Check material has been properly heat treated. To study various mode of mechanical fracture. Types of Microscopy  1. Optical Microscopy It is defined as, " microscopy in which visible light and system of lenses to magnify images of small samples " . Upper limit magnification is 2000x . It consists of two major systems, which are Magnification System   ↠  have lenses to magnify. Illuminating ...

Introduction  Existence of perfect crystals (without defects) are ideal. Instead, we have kinds of imperfection. Ques: Why study imperfections in Solids? When pure metals alloyed (addition of impurities ) like Sterling Silver ↣ 92.5 % Ag and 7.5 % Cu , Cartridge Brass ↣ 70 % Cu and 30 % Zn . These impurities play an important role in semiconductors properties, steel composition, etc. Atomic defects are responsible for reduction gas pollutants emissions in automobiles. Ques: How polluting gases converted into non-pollutant gases? Ans: Molecules of pollutant gases become attached to surface defects of crystalline material. Hence it convert into less-polluting substance. Types of Defects (Imperfections) in Solids There are four types of defects: Point (or Zero-D) Defects Linear (or 1-D) Defects  Planar (or 2-D) Defects  Bulk (or 3-D) Defects 1. Point Defects It is defined as, " defects associated with one or two atomic position " . Point defects are further divided into tw...