Project 2: Overaging of Al 7075
Group 2 - MSE 527L
Objective
Experimentally perform precipitation of Aluminium alloy 7075
Determine the effect of artificial ageing on hardness of Al-7075
Determine hardness of the alloy before and after the ageing process
Observe for optimum time duration of ageing of the alloy at a particular temperature to obtain maximum strength
Compare the differences in mechanical properties, such as ductility, tensile strength, yield strength, modulus of elasticity, and strain hardening exponent at different aging times.
Aluminium 7075●Ultimate Tensile strength : 74,000 psi - 78,000 psi
●Yield strength : 63,000 psi - 69,000 psi
●Material density : 2.810 g/cubic cm
●Specific gravity : 2.81
●Melting point : 900° F
●Modulus of Elasticity Tension : 10.4
●Modulus of Elasticity Torsion : 3.8
●High strength and excellent properties at low temperatures
●Commonly used in aircraft and aerospace applications
●Hardens by precipitation heat treatment
●Electrical conductivity is 36% of copper
Rockwell Hardness Test
●Measures permanent depth of indentation produced by load on the indenter
Depending upon hardness of material indenter to be used
The test axis should be within 2-degrees of perpendicular for correct loading
We perform this test on Al-7075 samples before and after ageing to observe the change
Background
Precipitation Hardening/Age HardeningFormation of extremely small dispersed 2nd phase particles
GP Zones
Effects on strength and hardness
OveragingWhen precipitation hardening has gone too far
Background
Tensile Test
All samples were subjected to tensile test to obtain mechanical properties after the aging
From stress and strain curve obtained following properties
Yield strength (YS)
Ultimate tensile Strength (UTS)
Ductility
Young’s Modulus (E) (YM)
Strain Hardening Exponent (n)
Procedure
7075 Aluminum samples were labeled and the initial rockwell Hardness was measured (Ten samples including two reference samples)
Samples were subjected to over aging at the 320 ºF (160 ºC) for 0,12,24,36,48 hours (Two samples at each time variant were taken for data accuracy)
Rockwell Hardness and conductivity was measured after the overaging process
Samples were then subjected to tensile test to compare the mechanical properties differences due to aging process.
Hardness
Conductivity
Stress/Strain Curves
Tensile Strength
Yield Strength
Ductility
Modulus of Elasticity
Strain Hardening Exponent
Microstructure
Sample 1 100X Longitudinal
Sample 1 100X Transverse
Microstructure
Sample 3 100X Longitudinal
Sample 3 100X Transverse
Microstructure
Sample 5 100X Longitudinal
Sample 5 100X Transverse
Microstructure
Sample 9 100X Longitudinal
Sample 9 100X Transverse
Microstructure
Sample 1 500X Longitudinal
Sample 9 500X Longitudinal
Microstructure
Sample 1 500X Transverse
Sample 9 500X Transverse
APPLICATIONS:● High strength to Density ratio: Transport, Aviation, Marine, Automotive● The strength and lightweight characteristics enhances the
applications in other fields. ● Other applications: Rock climbing equipment
Bicycle components
Inline skating frames
Hang glider airframes
● The hobby grade models typically use 7075 or the 6061 for the
chassis plates.
APPLICATIONS: ● Interesting Application: Manufacturing of upper and lower receivers as
well as the extension tubes for the high quality M16 Rifles in American military.
● Desert Tactical arms, SIG sauer and French armament company use it for their precision rifles.
● Common applications: camping knife and fork sets.● Wide use in mold manufacture: High strength
low density
Thermal properties
Ability to highly polished
References1. "Heat Treatments: Introduction." Heat Treatments: Introduction. N.p., n.d. Web. 17 Apr. 2013.
<http://www.efunda.com/processes/heat_treat/introduction/heat_treatments.cfm>.
2. "Age Hardening." Bluewater Thermal Solutions. N.p., n.d. Web. 17 Apr. 2013. <http://bluewaterthermal.com/age-hardening/>.
3. T. V. Rajan, C. P. Sharma, Ashok K. Sharma. “Heat Treatment: Principles and Techniques” 15ed. New Delhi: Prentice-Hall, 2006. 336-8.
http://books.google.com/books?id=A2QG3UssqKUC&pg=PA336&lpg=PA336&dq=gp+II+zone&source=bl&ots=Gmso2xnIks&sig=dsRTDlPIE0tyo2qF4YhpUGNLIsU&hl=en&sa=X&ei=tzJ_UaSRFOLtiwKqooDgAQ&ved=0CDoQ6AEwAQ#v=onepage&q=gp%20II%20zone&f=false
4. Effect of Ageing on Microstructure and Mechanical Properties of Bulk, Cryolled and Room temperature rolled Al 7075 Alloy by Sushantha Kumar
Panigrahi, R Jayaganthan; 2011.
5. "Rockwell Hardness Test Method | Newage Testing Instruments." Rockwell Hardness Test Method | Newage Testing Instruments. N.p., n.d. Web. 29
Nov. 2015.
6. "Rockwell Hardness Testing." Rockwell Hardness Testing. N.p., n.d. Web. 29 Nov. 2015.
7. "WWW.BUEHLER.COM." An ITW Company. N.p., n.d. Web. 29 Nov. 2015.
Questions