Some Elements of Equilibrium Diagrams for Systems of Iron ...
Chapter 4 Equilibrium Phase Diagrams and The Iron-Carbon system
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Transcript of Chapter 4 Equilibrium Phase Diagrams and The Iron-Carbon system
Phases
A phases is simply a form of material possessing a characteristic structure and properties.
A phases has a definable structure, a uniform and identifiable chemistry.
And distinct boundaries or interfaces that separate it from other different phases.
Equilibrium Phase Diagrams
is a graphic mapping of the natural tendencies of a material or a material system.
There are three primary variable to be considered: temperature, pressure and composition
Pressure-Temperature (P-T) diagram
Diagram maps the stable form of water for various conditions.
The region boundaries denote the melting and boiling point.
It has important to make freeze drying.
Temperature-Composition(T-C) diagram
At atmospheric pressure and variations more likely to occur in temperature and composition.
Cooling Curves
The equilibrium phase diagram is collective presentation of cooling-curve data for an entire range of alloy compositions
Solubility Studies
Can ice retain some salt in a single phase solid solution?
Can solid salt hold some water and remain a single-phase?
How much, and does the amount vary with temperature?
We called solubility limit.
Lead-tin equilibrium phase diagram
Solvus line: เส้�นแบ่�งระหว่�างของแข�งเฟส้เดี�ยว่และของแข�ง 2เฟส้
Complete solubility in both liquid and solid states
Liquidus line – เหน�อเส้�นน��เป็�นส้ารละลายในเฟส้เหลว่
Solidus line – ดี�านล�างของเส้�นน��เป็�นส้ารละลายในเฟส้ของแข�ง
Freezing range: Between the liquidus and Solidus
Partial solid solubility
At the point of max solubility, 183oC
Lead can hold up to 19.2 wt%
If T is decreased, the amount of solute that can be held in solution decreased.
Utilization of diagramที่��อ�ณหภู!มิ#และส้�ว่นผส้มิหน%�งๆน'�นจะบ่อกไดี�ว่�า
• The phase present เป็�นเฟส้ของอะไร –ของแข�ง?, ของเหลว่?, ของแข�งโครงส้ร�าง?
• The composition of each phase ป็ร#มิาณของแต่�ละเฟส้ ของแข�ง – ?%, ของเหลว่ ?%
• The amount of each phase presentส้�ว่นผส้มิในแต่�ละเฟส้ ในของแข�งมิ�ส้าร – A อย!� ?% ส้ารB อย!� ?%, ในของเหลว่มิ�ส้าร A อย!� ?% ส้ารB อย!� ?%
Equilibrium Phase Diagrams: T-C Diagram
ส้�ว่นผส้มิในแต่�ละเฟส้ ในของเหลว่–มิ�ส้าร A อย!� ?% ส้ารB อย!� ?%
a – S2 x 100%
L2 – S2
Iron-Carbon Equilibrium Diagram
Eutectoid
Eutectic
Peritectic
Steel, compose primarily of iron and carbon
Iron-Carbon Equilibrium Diagram
a body-cubic solid that is stable down to 1394oC, know as delta-ferrite.
From 1394oC to 912oC (FCC), know as austenite.
Alpha-ferrite (BCC) below 912oC
Iron-Carbon Equilibrium Diagram
At 1495oC, a peritectic reaction. At 1148oC, a eutectic with composition of
4.3% carbon 2.11% carbon are classified by the general
term cast iron At 727oC, a eutectoid with composition of
0.77% carbon. Alloy with less than 2.11% carbon, know as steels
Steels and the simplified iron-carbon diagram
The key transition will be the conversion of austenite to the two-phase ferrite plus carbide mixture.
Steels and the simplified iron-carbon diagram
Pearlite (ferrite + cementite) Eutectoid composition (0.77%C)
Austenite0.77%C; FCC Ferrite0.02%C; BCC + Cementite6.67%C
Steels and the simplified iron-carbon diagram
Hypoeutectoid steels (ferrite + pearlite) less than eutectoid composition
Hypereutectoid steels (cementile + pearlite) greater than eutectoid composition
Cast Irons
Iron-carbon alloys with more than 2.11% Wide variety properties. Contains iron, carbon, silicon, manganese,
sulfur, phosphorous อาจที่.าให�เก#ดี Graphite หร�อ Cementite Graphite form by slow cooling Cementite form by fast cooling
Cast Irons
Graphite
• เย�นต่'ว่ลงช้�าๆ• ป็ร#มิาณคาร0บ่อน C, Si ส้!ง• ใช้�เว่ลาบ่�มิต่'ว่• มิ�ส้�ว่นผส้มิของ S, P, Al, Mg, Sn, Cu, Co
Cementite
• เย�นต่'ว่ลงเร�ว่• ป็ร#มิาณคาร0บ่อน C, Si ต่.�า• มิ�ส้�ว่นผส้มิของ Ti, V, Cr, Zr, Mn, Mo
Cast Irons
Gray Cast Iron 0.5-4.0%C, 1.0-3.0%Si, 0.4-1.0%Mn ผลของ Graphite ที่.าให�
• Brittle
• Excellent compressive strength
• Excellent machinability
• Good resistance to adhesive wear
• Outstanding vibration damping