MEGR 2180 Manufacturing Systems Lecture Notes PDF

MEGR 2180 Manufacturing Systems (and processes) Lecture Series 4: Alloying, Phase Diagrams  Behavior and Manufacturing Properties of Materials Physical and Structure of Mechanical Prope...

MEGR 2180 Manufacturing Systems (and processes) Lecture Series 4: Alloying, Phase Diagrams  Behavior and Manufacturing Properties of Materials Physical and Structure of Mechanical Property Chemical Materials Properties Modification Properties Atomic Bonds Strength Density Heat Treatment Crystalline Ductility Melting Point Precip. Hard. Amorphous Elasticity Specific Heat Annealing Hardness Thermal Cond. Tempering Toughness Thermal Exp. Surface Treat. Fatigue Electrical Cond. Alloying Creep Oxidation Reinforcements Corrosion Composites Lamination Fillers 2  Student Outcome - I was able to characterize metals with respect to their fundamental structures and mechanical properties. - I was able to describe the basic principles and processes in metal casting. - I was able to describe the basic principles and processes of forming and shaping. - I was able to describe the basic principles and processes of different metal removal methods. - I was able to describe the basic joining techniques. - I was able to describe several non-traditional machining processes including IC manufacture. - I had confidence in the following design related topics: material selection, heat treatment and alloying 3  Engineering Materials Metals Plastics Ceramics Composites Oxides Reinforced Ferrous Non- Ferrous Nitrides Plastics Carbides Metal-matrix Iron Aluminum Glasses Ceramic Matrix Steels Copper Glass Laminates Titanium Graphite Tungsten Diamond Thermoplastics Thermosets Elastomers ABS Epoxies Rubbers Nylon Phenolics Silicones Polyethylene Polymides Polyurethanes 4  Today’s questions “If we ask the right questions, we can change the world with the right answers.” Ogwo David Emenike What is alloying? Why is it useful? How to read a Phase diagram Heat Treatments When to use a TTT diagram 5 Where Alloys are Used The mixing of metals and semi-metals in the molten state is called alloying Composed of multiple elements. The principle component is a metallic element Alloying is performed to change the physical properties of a metal 6  Effects of Carbon: Mechanical Properties of Steel Mechanical Properties change with composition. Imagine the potential applications - Low Carbon(.3 &.6 - Springs, cutlery, cable Effect of carbon content on the mechanical properties of carbon steel 7 Figure 3.33 from Kalpakjian and Schmid, 5th ed  What is the elongation of 0.3% Carbon Steel? Click Present with Slido or install our Chrome extension to activate this ⓘ poll while presenting. 8  What is the elongation of 0.3% Carbon Steel? Click Present with Slido or install our Chrome extension to activate this ⓘ poll while presenting. 9  Which manufacturing processes involves melting, solidification etc? Click Present with Slido or install our Chrome extension to activate this ⓘ poll while presenting. 10 https://www.youtube.com/watch?v=h2RiLz1-v4Q 11 https://www.youtube.com/watch?v=JXkKYAQ1rXs 12  Alloying If the atoms are the same of each other they will crystallize as a single set of crystals – all the atoms will behave as if they are similar. A single phase Solid solution is said to form If the different elements crystallize separately to form different crystals that meet at grain boundaries then the resulting structure is referred to as a Phase Mixture 2 phase w/in the grain Different structures or each grain is different crystal 13  Alloying - Solid Solution In a solid solution the crystal structure is the same as that of the solvent (parent metal). The Solute atoms are distributed through in crystal. The solution may be formed in two different ways: Substitutional Interstitial 14  Alloying - Solid Solution -Substitution Substitutional alloying: o Atoms of the two metals do not differ in diameter more than 15% o The two metals must have a similar crystal structure. An example is Brass Substitutional - Solute is Zinc - Solvent is Copper - (Elements are beside each other on periodic table) Another example is that of Monel; - A mixture of Copper and Nickel - (Elements are also beside each other on periodic table) 15  Alloying –Solid Solution - Interstitial Interstitial: Solute atoms positioned between the atoms in the solvent Conditions Interstitial – Atomic radius of the solute must be less than about 60% of the solvent radius An example is Steel – Solvent is Iron (.126 nm) – Solute is Carbon (.077 nm) – Amount of carbon significantly affects material properties 16  Solidification of Pure Metals Pure 17  What if the metal is not Pure? Click Present with Slido or install our Chrome extension to activate this ⓘ poll while presenting. 18  Solidification of Pure Metals Which region would you expect the solidification process curve for an alloy to differ most from that of a pure metal? 19  Which region would you expect the solidification process curve for an alloy to differ most from that of a pure metal? Click Present with Slido or install our Chrome extension to activate this ⓘ poll while presenting. 20  Phase diagrams come to the rescue! A Phase has a definable structure, a uniform and identifiable chemistry (aka composition) and distinct boundaries or interfaces that separate it from other different phases. A Phase diagram (also called an equilibrium diagram) illustrates the relationship between temperature, composition and the phases present in a particular alloy. 21 Copper-nickel phase diagram: Simple Phase Diagram 22  What is the melting point of Ni and Copper, respectively? Click Present with Slido or install our Chrome extension to activate this ⓘ poll while presenting. 23  Copper-nickel phase Diagram 40% Cu, 60% Ni Point a: 40% Cu - 60% a b Point b: 40% Cu - 60%Ni 24  Solder Let’s take a look at my favorite solder to see a good attribute for small electronic devices. Atomic sizes Lead: 0.175 nm Tin: 0.140 nm Why is the 37% lead in the solder and not some other percentage? 25 Lead (.175 nm) - Tin (.140 nm) Phase Diagram 26  What is the transition temperature (Celcius) of a 75% Sn - 25% Lead alloy from solid to completely liquid? Click Present with Slido or install our Chrome extension to activate this ⓘ poll while presenting. 27  Two critical points on a phase diagram Eutectic: An isothermal reversible reaction in which a liquid solution is converted into two or more intimately mixed solids on cooling Eutectoid: An isothermal reversible reaction in which a solid phase is converted into two or more intimately mixed solids on cooling 28  Iron Carbon Phase diagram Two critical points on a phase diagram Eutectic - Pig Iron isothermal reversible reaction liquid solution is converted into two or more intimately mixed FCC solids on cooling Liquid → Solid Eutectoid - Phase transition isothermal reversible reaction solid phase is converted into two or more intimately mixed solids on cooling Solid → Solid B. Mullany - 29  Importance of Fe-C Phase diagrams Why do we need to know about Iron-carbon Systems ? % Carbon content of different materials: Up to 0.008% → Pure Iron.6 → High Carbon Up to 2.11% → Steel Up to 6.67% → Cast Iron 30  Solidification of water https://www.youtube.com/watch?v=czmQ2_ymaOo 31  Alloying Ferrite 1220X. (dark areas) Cementite (White areas) Ɣ Austenite Pearlite Martensite Single phase FCC Structure Lamellar aggregate of interstitial supersaturated solid Fine non-lamellar structure solution of C in Fe – Ductile at elevated temperatures Ferrite and Cementite High hardness – Good formability –important for Hard, strong, and ductile Body centered tetragonal lattice. manufacturing not particularly tough. meter-size shafts and plates – Nonmagnetic FERRITE ɑ: BCC Structure Microstructure is needle-like Stable at high temperatures desirable strength-ductility combinat. has little engineering relevance hardest and strongest Soft, Ductile, and Magnetic microstructure, harder than pearlite CEMENTITE (Fe3C): Also called as Carbide the most brittle. not as hard as martensite Hard and brittle intermetallic compound Significantly affects the properties of steel larger grains smaller grains 32 Transition can be larger grains smaller grain size 33  34 https://www.youtube.com/watch?v=OQ5lVjYssko https://www.youtube.com/watch?v=wkrspFx9yZc 35 36 37 38 39  Some of the different phases in Fe-C systems Ɣ Austenite AUSTENITE: Single phase FCC Structure – Ductile at elevated temperatures – Good formability –important for manufacturing – Nonmagnetic 40  Some of the different phases in Fe-C systems CEMENTITE (Fe3C): Pearlite – Also called Carbide – A hard and brittle intermetallic compound that has Cementite a significant influence on the properties of steel (White areas) FERRITE ɑ: BCC Structure – Only stable at high temperatures and has little Ferrite (dark areas) engineering relevance – Soft, Ductile, and Magnetic PEARLITE: lamellar aggregate of Ferrite and Cementite 41  Heat treatment Combination of heating and cooling operations Timed and applied to a metal or alloy in the solid state Achieve desired properties Modify the microstructure of alloys to imparted different mechanical properties Effects of thermal treatment depend on – The composition and microstructure of the alloy, – The degree of cold work, – The rates of heating and cooling, – The temperatures and temperature ranges, etc. 42  Heat treatments to remember in this class Topics to focus Importance of Heat Treatment Quenching Annealing Tempering Use of the TTT curves Use of Phase Diagram https://www.youtube.com/watch?v=HsVnswfHGXM 43  We can increase the hardness of steel HT of steel (hardening): 1. Heat up to cause a phase change 2. Rapid cooling (quenching) to form new phase (martensite) Martensite: It is an interstitial supersaturated solid solution of carbon in iron having body centered tetragonal lattice. Its microstructure 1. is characterized by a needle like pattern 2. 1220X. 44  Which of the following is NOT a quenching medium? A. Water B. Alcohol C. Air D. Brine 1. Martensite: It is an interstitial supersaturated solid solution of carbon in iron having body centered tetragonal lattice. Its microstructure is characterized by a needle like pattern 2. 1220X. 45  Which of the following is NOT a quenching medium? A. Water B. Alcohol C. Air D. Brine 1. Martensite: It is an interstitial supersaturated solid solution of carbon in iron having body centered tetragonal lattice. Its microstructure is characterized by a needle like pattern 2. 1220X. 46  Annealing Annealing 1. Usually done after cold working 2. Heat up to convert steel into austenite 3. Slow, controlled cooling back to room 1. temp in an oven Outcomes … 2. - Hardness up/down - Machinability up/down - Residual Stress up/down 47  Annealing Annealing 1. Usually done after cold working 2. Heat up to convert steel into austenite 3. Slow, controlled cooling back to room 1. temp in an oven Outcomes … 2. - Hardness up/down - Machinability up/down - Residual Stress up/down 48  Tempering Tempering 1. Usually done after quenching 2. Heat up hardened steel, but induce no phase change 3. Slow, cooling back to room temp Outcomes before quenching… - Residual Stress up/down - Hardness up/down - Toughness up/down 1. 2. 49  Tempering Tempering 1. Usually done after quenching 2. Heat up hardened steel, but induce no phase change 3. Slow, cooling back to room temp Outcomes before quenching… - Residual Stress up/down - Hardness up/down - Toughness up/down 1. 2. 50  The effect of tempering Heat treatment variables Temperature Time Most treatments are constant- temperature processes. (Carbon diffusion is involved in the transformation.) Tensile and yield strength and ductility (%RA) versus tempering temperature oil-quenched alloy steel (type 4340). 51 52  Another useful chart: Isothermal Diagrams Isothermal-transformation diagrams define the transformation of Austenite as a function of time at constant temperatures. They are also called Time- Temperature – Transformation (TTT) curves. Each curve represents only one alloy composition, an iron- carbon alloy of eutectoid composition. 53  Another useful chart: Isothermal Diagrams Austenitic A eutectoid steel composition is Perlite quenched to 650oC and held for 20 seconds and then quenched to 450oC Bainite where it is held for 1000 seconds. What is the microstructure after this process? HERE for explanation Martensite https://www.youtube.com/watch?v=Q hS8rPCKdgw 54  Another useful chart: Isothermal Diagrams A eutectoid steel composition is quenched to 650oC and held for 20 Austenitic seconds and then quenched to 450oC Perlite where it is held for 1000 seconds. What is the microstructure after this process? Bainite HERE for explanation https://www.youtube.com/watch?v=QhS8rPCKdgw Martensite 55  Case Hardening Many industrial applications require a hard wear Kantana’s Alloy resistant surface called the case and a relatively soft tough inside called the core gears, bearings,cams, tool, dies, etc. This technique is called case hardening Case hardening is performed by adding other elements to the surface or by special heat treatments. 56  Case Hardening Other method involve heat Treating: – Flame Hardening – heating surface with a flame and quenching – Induction hardening – heating surface with high frequency induced This photo shows ways on 16" vise base being hardened utilizing flame hardening. current and quenching 57  Case Hardening One method involves adding surface elements: – Carburizing – adding carbon – Carbonitriding – adding carbon and nitrogen – Nitriding – adding nitrogen – Many recipes exist 58  Risks in heat treatment Heat treatments can cause problems such as cracking, distortions etc. Parts incorrectly case hardened (for example through hardened instead) can fail due to lack of toughness Martensitic and quench cracks Distortions must be corrected on precision parts by finish grinding (usually) Grinding cracks 59  Jominy End Quench test (Click HERE) Explain why stress strain curves are so important, detail the information that can be extracted from the curve and from looking at the tensile sample after fracture Hardenability curve is the dependence of hardness on distance from the quenched end. The higher the hardness levels further away from the quenched end the more hardenable the alloy. Test standards: American Society for testing and Materials (ASTM) Method A 255 Society of Automotive Engineers (SAE) standard J406 60  Copper-nickel phase diagram: How much of each phase do we have? Create a lever “balanced” at the nominal composition, C0. CS represents solid composition. CL represents the liquid composition 61  Write down the keywords you remember about alloying and Phase Diagrams Click Present with Slido or install our Chrome extension to activate this ⓘ poll while presenting.  Further Professional Reference in Metallurgy https://www.linkedin.com/company/metalurgical-engineering/posts/?feedView=all 63