Metallic Materials - Mechanical Behavior

Metallic Materials

• Metallic materials encompass a wide range of elements and alloys
• Approximate 50 metallic elements are present, but only a few are extensively used in engineering
• Iron (Fe) is the most significant metallic element, crucial for steel and cast iron production
• For structural applications, the hierarchy of importance for metals typically follows this sequence: Fe > Al > Cu > Ni > Ti.

Related Courses

• MLZ 216: Mechanical Behavior of Materials (4th semester)
• MLZ 327: Mechanical Behavior of Materials II (5th semester)
• MLZ 315: Electrochemistry (5th semester)
• MLZ 335: Metallic Materials I (5th semester)
• MLZ 336: Metallic Materials II (6th semester)
• MLZ 447: Materials Processing Laboratory II (7th semester)
• MLZ 455: Heat Treatment (7th semester)
• MLZ 457: Manufacturing with Materials (7th semester)
• MLZ 459: Degradation of Engineering Materials (7th semester)

Definition of a Metal

• Metals are electropositive elements and their alloys
• The electron bond structure of a metal is characterized by a partially filled valence band
• Metals readily form positive ions (cations) and have metallic bonds

Periodic Table of Elements

• A chart displaying arrangement of chemical elements in a tabular form
• This representation shows atomic number, atomic weight, chemical symbol, etc of each element
• Organized based on recurring chemical properties, typically based on atomic number

Properties of Metals

• Shiny: Metals possess a characteristic lustrous appearance
• Ductile & Malleable: Metals can be drawn into wires (ductile) and hammered into sheets (malleable)
• High Melting Temperature: Metals typically have high melting points
• Relatively Hard: Majority of metals are hard materials
• Good Conductors of Heat & Electricity: Metals are known for their excellent conductivity for heat and electricity
• Sound: Often associated with strength and durability of metals

Metals & Alloys

• The usage of metals is largely influenced by economic considerations
• Factors like ore availability and extraction complexity play a role
• Extractive advancements have led to significant changes in the overall picture

Ferrous Alloys

• Most common type of metal
• Used extensively in various construction applications
• Abundant Fe-containing compounds
• Relatively low cost for extraction
• Tailored mechanical and physical properties

Fe as a Base Material

• High melting point (1538°C)
• Maintains strength at high temperatures (450°C)
• High elastic modulus (205 GPa)
• Easy to recycle and produce
• Heat treatable for wide range of strength and toughness
• Easily alloyed with various elements (Cr, Ni, Co, Cu, etc.)

Refining of Steel from Ore

• The process involves reducing iron ore to metal using coke
• Limestone is used to purify the molten iron.
• Chemical reactions liberate carbon dioxide and other gases/compounds.

Disadvantages/Limitations of BCC phase

• Ductile-to-brittle transition temperature is low
• Prone to brittleness at low temperatures
• High density (7.87 g/cm³)
• Relatively low conductivity
• Poor corrosion resistance

Classification of Metals

• Metals are classified into ferrous and non-ferrous categories
• Ferrous metals include steels and cast iron
• Non-ferrous metals include copper alloys, aluminium alloys, titanium alloys, magnesium alloys, and superalloys

Steels

• Consist of iron and other elements
• Properties are influenced by Carbon percentage
• Varying carbon content categorizes them into low-, medium-, and high-carbon steels; further categorized based on alloying element percentages
• Varying mechanical and chemical properties, based on carbon and other alloying element content.

Cast Iron

• Ferrous alloys with > 2.1 wt% carbon
• Often commonly 3-4.5 wt% of carbon
• Low melting point
• Brittle
• Includes various types—gray iron, ductile iron, white iron, and malleable iron

Types of Cast Iron

• Gray iron: graphite flakes, strong under compression, excellent damping, wear-resistant
• Ductile iron: Mg or Ce additions, graphite in nodules, superior ductility
• White iron: low Si content, high hardness, brittle appearance, high cementite content
• Malleable iron: heat treatment, graphite in rosettes, increase ductility

Non-ferrous Alloys

• Non-ferrous alloys are categories encompassing alloys without iron as a primary component
• Cu alloys (brasses, bronze, Cu-Be), Al alloys, Mg alloys, Ti alloys, noble metals, and refractory metals are subtypes of non-ferrous alloys
• Properties vary widely for each alloy type.

Properties of Metals and Alloys

• Tables summarizing cost, density, strength, fracture toughness, and thermal conductivity for different steel, light, and heavy non-ferrous alloys.

This quiz delves into the fundamentals of metallic materials, focusing on their properties and applications in engineering. It covers key metallic elements, their importance, and classifications, essential for students in related mechanical behavior courses.