MSE PhD Defense - Justin Lamb

Date: Wednesday, December 2, 2015

Time: 3:15 PM

Location: Love 210

Committee:

Dr. Thomas H. Sanders Jr, MSE (Adviser)

Dr. Preet Singh, MSE

Dr. Naresh Thadhani, MSE

Dr. Arun Gokhale, MSE

Mr. Victor Dangerfield, Universal Alloy Corporation

Title:

Decomposition and its effects on mechanical properties in Al-Zn-Mg-Cu alloys

Abstract:

The effects of variations in composition on the decomposition process in Al-Zn-Mg-Cu alloys (i.e. – 7xxx-series aluminum alloy) were studied emphasizing their effect on mechanical properties.  Several experimental quaternary alloys were studied to compare their behavior with commercial 7xxx-series alloys.  The investigation included studies on the effects of natural aging, artificial aging, quench sensitivity, precipitate free zone formation, corrosion, stretching, and homogenization.  Fluctuations in the main alloy elements/processing parameters can alter the precipitation process.  The purpose of this work is to quantify those changes using standard industrial techniques.  For example, it was found that natural aging prior to artificial aging was detrimental for strength in the T6 temper for alloys containing more than 1.0 wt.% Cu, and was shown to alter the coarsening kinetics in the over-aged condition (T7).  Conversely, for alloys with Cu contents less than 0.5% natural aging was shown to be beneficial for strength.  Altering the Zn:Mg ratio was also shown to effect natural aging response of an alloy in addition to introducing additional precipitation processes (T-phase).