L3-P1 and P2 Alloys and Heat treatment

What is a metal?

• Elements that are good conductors of electricity and heat, characterized by metallic bonds. (shared valece electrons).

• Non-directional, flexible bonding

• Ductility/malleability (formable)

• Reflectivity (shiny)

Alloys

Mixtures primarily consisting of metals, which display properties distinct from those of the individual components.

Phase

A region of material with distinct chemical and physical properties, often represented in phase diagrams.

Solute

An element or compound that is dissolved in a solution. (socker i teet)

Solvent

The phase that hosts the solute in a solution. (teet med sockret i)

Intermetallic

Metallic mixtures with a strict ratio of atoms, often leading to unique properties. (alloy är blandning utan proportioner)

Equilibrium

A state where a system is at its lowest energy, showing no spontaneous changes. For ex. if ice is places in room temprature, its equilibrium state is water, but it takes time for it to melt.

Ductility

The ability of a material to undergo significant plastic deformation before rupture.

Malleability

The ability of a material to deform under compressive stress.

Solution hardening

A process where the addition of solutes to a solvent metal enhances its strength. Due to solutes obstruct dislocation movement in the material.

Eutectic transformation

A transformation of a liquid melt into two solid phases. No mushy state, no liquid + solid

Tempering

A heat treatment process applied to martensite to adjust hardness and toughness. (causing gradual softening ang toghening)

Precipitation hardening

A method of strengthening alloys by allowing tiny particles from secondary phase to form within the alloy.

Overaging

A phenomenon where precipitates grow too large during aging, weakening the material.

Case hardening

A heat treatment process that hardens the surface of a material while maintaining a tougher core. Its principles:

Local plastic deformation near the surface 

Modification of chemical composition near the surface 

Rapid heating and cooling of the surface 

Hardenability

The capability of a steel to harden in depth under a quench. Refers to how rapidly a steel must be cooled to achive martensite. Hardenability of steel depends on alloying and austenite grain size. A Jominy test measures hardenability.

Martensite

A hard, brittle microstructure formed from austentite during rapid cooling. Is not on a phase diagram since its never in eqilibrium.

Cementite

A hard compound of iron and carbon, primarily represented as Fe3C.

Ferrite

A soft, ductile phase in iron-carbon alloys, represented as α-Fe.

Austenite

A high-temperature phase in iron alloys, represented as γ-Fe.

Lever rule

A calculation used to determine the proportions of phases in a two-phase region of a phase diagram.

Carbon steels

Steel alloys primarily composed of iron and carbon.

Stainless steels

Steel alloys containing chromium that enhance rust resistance.

Light alloys

Alloys, such as aluminum and magnesium, known for their high strength-to-weight ratios.

Refractory metals

Metals with high melting points, such as tungsten and molybdenum.

Superalloys

Alloys designed to withstand extreme temperatures and environments, often based on iron, cobalt, or nickel.

Precious metals

Metals, including gold and silver, that have significant economic value, often due to their rarity and aesthetic characteristics.

Nonferrous alloys

Alloys that do not contain significant amounts of iron, such as aluminum and copper alloys.

What is alloying?

The process of mixing two or more metals, or a metal with non-metals, to create an alloy with enhanced properties.

Single phase alloy

An alloy that consists of only one phase, exhibiting uniform properties throughout the material.

Dual phase alloy

An alloy that contains two distinct phases, often enhancing properties such as strength and ductility by combining different microstructures.

How does dislocation movement in crystals change during solution hardening?

In solution hardening, the presence of solute atoms hinders the movement of dislocations in crystals, increasing the strength and hardness of the material. Increasing the yield stress.

What is a eutectoid transformation?

Like eutectic, but from solid to a different sollid

What is quenching?

A rapid cooling process usually involving immersing a hot metal in water or oil to harden it by transforming its microstructure. Cooling rates for quench media: salt water 5x, water 1x, oil 0.3x, still air 0.02.

austenitizetion

steel gets heated to austonite

Process stål hardening austenitization, quenching and martensite

is a heat treatment process that involves heating steel to form austenite, followed by rapid cooling to form martensite, resulting in increased hardness.

Full annealing

Makes the steel very soft and ductile, by austenitization followed by slow cooling to grow coarse pearlite

Normalizing

Resets the material to standard properties, by austenitization followed by moderate cooling to grow fine pearlite

Spheroidizing

Softens and toughens pearlite structure by heating below austenitization temperature, breaking up cementite lamellae into spherical particles

Martensize hardening

Makes the steel very hard and brittle, by austenitization followed by rapid cooling (quenching), causing formation of martensite

Martensite tempering

Gradually softens and toughens martensite structure by heat treatment below austenitization temperature, causing martensite to break down into ferrite and cementite

What is solution treatment?

A heat treatment process that involves heating an alloy to dissolve solute elements, followed by rapid cooling (to avoid the secondary phase) to retain the solute in a supersaturated solid solution, enhancing strength and corrosion resistance.