Aluminum 7075 Microstructure and Current Research through the use of In-situ X-ray Diffraction By: Jay Schuren

Outline Why Al 7075? General Aluminum Overview Microstructure of 7075 Current Diffraction Research on Al 7075

Why Al 7075? Aluminum is an abundant resource Relatively cheap High stiffness/density and strength/density ratios Damage tolerant Corrosion resistant compared with conventional alloys

Uses of Al 7075 Gears and shafts Aircraft Other Aerospace and defense applications

General Aluminum Alloy Overview

Principal Aluminum Alloys Wrought alloys are divided into seven major classes Classes set by their principal alloy elements Strengthened by work hardening –1XXX, 3XXX, 4XXX, 5XXX Strengthened by heat treatment (precipitation hardening) –2XXX, 6XXX, and 7XXX The seven classes can be subdivided:

Overview 1XXX -Commercially Pure Al. 3XXX - Al. Manganese Alloys 4XXX - Al. Silicon Alloys 2XXX - Al. Copper Alloys 6XXX - Al. Mg. Si. Alloys 7XXX - Al. Zinc Alloys Work HardenedPrecipitate Hardened

7075 Microstructure

Ingot can form (Fe,Cr) 3 SiAl 12, Mg 2 Si and/or a pseudobinary eutectic made up of Al and Mg(Zn,Cu,Al)2. Heating causes iron rich phases to transform to Al 7 CuMg precipitates. Chromium is precipitated from supersaturated solution as Cr 2 Mg 3 Al 18 dispersoids, concentrated heavily in the primary dendrite region. Recrystallized grains are extremely elongated or flattened because of dispersoid banding, and unrecrystallized regions are made up of very fine subgrains in which boundaries are decorated by hardening precipitates 7075 Microstructure

Stable properties Higher strengths Improved corrosion resistance Lower rate of growth of fatigue cracks are. Aging at elevated-temperature can provide:

Diffraction Applied to 7075 Approach –Measure the changes in lattice spacing of the aggregate as the specimen is under load –Use X-ray diffraction (XRD)

Experimental Setup

Actual Al 7075 T6 Data Strain Pole Figures

Stress-Strain Curve for 7075 T6

In-situ X-ray diffraction provides a “snap shot” of the aggregate lattice strain Can invert lattice strain to find full strain tensor Validates micromechanical models What In-situ X-ray Diffraction gives us

References Aluminum: Properties and Physical Metallurgy by John Hatch Experimental measurement of lattice strain pole figures using synchrotron x rays by M. P. Miller Measuring crystal lattice strains and their evolution in cyclic loading by J- S. Park On the mechanical behaviour of AA 7075-T6 during cyclic loading by Turkmen Influence of modelling variables on the distribution of lattice strains in a deformed polycrystal, with reference to neutron diffraction experiments by Loge Elements of X-ray Diffraction by Cullity damentals/dispersoids.htmhttp:// damentals/dispersoids.htm Electrochemical Characterization of 7075 Aluminum Alloys Using The Microcell by Barbara N. Padgett