che 333 class7 precipitation hardening. 2010 nobel prize in physics materials breakthrough wins...
TRANSCRIPT
CHE 333 Class7
Precipitation Hardening
2010 Nobel Prize in Physics Materials breakthrough wins Nobel
By Paul RinconScience reporter, BBC NewsAndre Geim is based at the University of Manchester in the UKTwo scientists have shared this year's Nobel Prize for Physics for their "groundbreaking" work on a material with amazing properties.Andre Geim and Konstantin Novoselov, both at Manchester University, UK, took the prize for research on graphene. Used “sticky tape” to find material.
http://www.bbc.co.uk/news/world-11476301
Yesterday:-
I am contacting you to make you aware of NineSigma Request, RFP# 66654, "Transparent Conducting Graphene Coatings on Polymer Film Substrates."Our client, 3M, invites proposals for new graphene-based materials and/or processing methods able to deliver thin, optically transparent and highly conductive films on polymer film substrates
Precipitation Hardening
THIS WEEKS LAB - STARTING THIS AFTERNOON. A WRITTEN REPORT WILL BE REQUIRED ALONG
WITH A GROUP VERBALREPORT. USE THE WEBSITE TO SEE THE STRUCTURE FOR THE REPORTS.
PRECIPITATION HARDENING is a NON EQUILIBRIUM heat treatment procedure.
Process involves a solution heat treatment, that is transformation to a single phase, followed by a quench, again to suppress a phase transformation. The major difference between age hardening and martensite transformation is that the high temperature phase is retained to low temperatures.
Phase Diagram for Age Hardening
Need single phase region
Solution treat in zone, hold for a period
of time so phase dissolves.
Upon quench to below solvus, phase
diagram predicts + should be
present. However, quench suppresses
phase formation, so only phase
at room temperature.
Conditions for age hardening.
1. Alloy system
2. Single Phase region and a two
phase region
3. Decreasing solid solubility with
temperature
4. Slugish diffusion of solute.
Aluminum alloys, copper alloys, steels,
Processes
Solution treat in single phase regionthen quench. At room temperature,only a phase is present. The phasediagram predicts +, so no . Composition of single phase a at lowtemperature is then the average, as it cannot follow the >+ solvus.The a has considerably more of elementb in it than the phase diagram suggests.It is know as a “Super Saturated SolidSolution” It is again a metastable phasein some cases.
Time Temperature HistoryThermal history for an aluminum alloy
age hardening sequence is shown.
After quench, an ageing treatment
is applied. The ageing treatment
involves heating the material into
the two phase regions of the
equilibrium phase diagram.
The thermal energy allows
atoms and vacancies to move
around and form new phases.
This is called the ageing sequence.
The first phases formed are not
the equilibrium ones.
Phase SequenceThe first phase to form is often called GP zones after Guinier and Preston. GP zones are clusters
of solute atoms, with the same crystal structure as the single phase, FCC for aluminum alloys.
Al 0.143 nm, Cu 0.128nm atomic radius
Phase TransformationsAfter the first GP zones are formed, for the Al-Cu system a second GP zone occurs which also has a
FCC structure. This is the ” phase.
For Al-Cu there is a further phase the ’ phase which is an ordered structure consisting of eight FCCunit cells to form a cube. The lattice parameters are a=b= 4.04A, c =5,8A
PropertiesThe properties are a function of structure, which is controlled by the ageing time and temperature.
GP zones are FCC and have the same slip system as the FCC phase – called underaged.
The ” phase are ordered strutures and harden more.
The ’ phase hardens as it also an ordered stucture, but overages..
Optimum properties come from the ”and ’ phase combination prior to overaging.
StructuresGP zones in Al-4%Cu, 540C for 1hour130C for 16 hours1,000,000 mag{100} planes, 100A diam10% atomic diameter differencegrowth as plates.
GP zones Al-16%Ag520 C160C for 5 days200,000 magMinimal strain, spheres
Peak and Over Aging
” in Al-4%Cu540C130C for 24 hours800,000 magPlates on {100}
’ in Al-4%Cu540C solution treatment160C for 72 hours25,000 mag.