Examples of Aluminium Fractography Professor M Neil James mjames@plymouth.ac.uk Department of Mechanical & Marine Engineering University of Plymouth Drake Circus, Plymouth PL4 8AA ENGLAND Fractography Resource - mjames@plymouth.ac.uk

Contents – Use the hyperlinks to navigate around this resource Bend fatigue of 6261-T6 alloy Torsion fatigue of 6061-T6 alloy Ductile fracture of 6061-T6 alloy Fatigue of 8090-T8511 Al-Li alloy Ductile fracture of 8090-T8511 Al-Li alloy Bend fatigue of friction stir welded 5383-H321 alloy Ductile fracture of 5383-H321 alloy Defects in an aluminium-silicon-magnesium casting alloy Fractography Resource - mjames@plymouth.ac.uk

Bend fatigue of 6261-T6 alloy Al 0.74Mg 0.63Si 0.19Fe 0.26Cu 0.025Zn 0.020Ti Peak aged - PS = 282 MPa – Parent Plate (I-beam flange) Linear growth rate regime ~ 10-4 mm/cycle Arrows indicate grain boundaries Original magnification 80x Fractography Resource - mjames@plymouth.ac.uk

Bend fatigue of 6261-T6 alloy Al 0.74Mg 0.63Si 0.19Fe 0.26Cu 0.025Zn 0.020Ti Peak aged - PS = 282 MPa – Crack at weld toe of cover plate Linear growth rate regime ~ 10-4 mm/cycle The HAZ appears to be embrittled, and cleavage facets are present Original magnification 20x Back to Contents Fractography Resource - mjames@plymouth.ac.uk

Torsion fatigue of 6061-T6 alloy Al 0.8-1.0Mg 0.4-0.8Si 0.70Fe 0.15-0.40Cu 0.25Zn 0.15Ti 0.15Mn Peak aged - PS = 312 MPa – extruded rod Crack initiation region Original magnification given by micron marker Fractography Resource - mjames@plymouth.ac.uk

Torsion fatigue of 6061-T6 alloy Al 0.8-1.0Mg 0.4-0.8Si 0.70Fe 0.15-0.40Cu 0.25Zn 0.15Ti 0.15Mn Peak aged - PS = 312 MPa – extruded rod Crack initiation region – smooth areas of slip band cracking are present Original magnification given by micron marker Fractography Resource - mjames@plymouth.ac.uk

Torsion fatigue of 6061-T6 alloy Al 0.8-1.0Mg 0.4-0.8Si 0.70Fe 0.15-0.40Cu 0.25Zn 0.15Ti 0.15Mn Peak aged - PS = 312 MPa – extruded rod Crack growth appears to have a component of MVC Original magnification given by micron marker Back to Contents Fractography Resource - mjames@plymouth.ac.uk

Ductile fracture of 6061-T6 alloy Al 0.8-1.0Mg 0.4-0.8Si 0.70Fe 0.15-0.40Cu 0.25Zn 0.15Ti 0.15Mn Peak aged - PS = 312 MPa – extruded rod Precipitate particles are present at the bottom of voids Original magnification given by micron marker Back to Contents Fractography Resource - mjames@plymouth.ac.uk

Fatigue of 8090-T8511 Al-Li alloy Al 2.37Li 1.19Cu 0.82Mg 0.11Zr Peak aged - PS = 300 MPa – large extrusion 120 mm by 100 mm Heat treatment leads to grain boundary precipitation of Al2CuMg, which affects crack growth IG regions are often present Original magnification given by micron marker Fractography Resource - mjames@plymouth.ac.uk

Fatigue of 8090-T8511 Al-Li alloy Al 2.37Li 1.19Cu 0.82Mg 0.11Zr Peak aged - PS = 300 MPa – large extrusion 120 mm by 100 mm Heat treatment leads to grain boundary precipitation of Al2CuMg, which affects crack growth IG regions are often present Original magnification given by micron marker Fractography Resource - mjames@plymouth.ac.uk

Fatigue of 8090-T8511 Al-Li alloy Al 2.37Li 1.19Cu 0.82Mg 0.11Zr Peak aged - PS = 300 MPa – large extrusion 120 mm by 100 mm Heat treatment leads to grain boundary precipitation of Al2CuMg, which affects crack growth Typical IG region at high magnification Original magnification given by micron marker Fractography Resource - mjames@plymouth.ac.uk

Fatigue of 8090-T8511 Al-Li alloy Al 2.37Li 1.19Cu 0.82Mg 0.11Zr Peak aged - PS = 300 MPa – large extrusion 120 mm by 100 mm Heat treatment leads to grain boundary precipitation of Al2CuMg, which affects crack growth 'Blocky' striated fatigue also occurs Original magnification given by micron marker Fractography Resource - mjames@plymouth.ac.uk

Fatigue of 8090-T8511 Al-Li alloy Al 2.37Li 1.19Cu 0.82Mg 0.11Zr Peak aged - PS = 300 MPa – large extrusion 120 mm by 100 mm Heat treatment leads to grain boundary precipitation of Al2CuMg, which affects crack growth Regions of 'normal' striated fatigue also occur Original magnification given by micron marker Fractography Resource - mjames@plymouth.ac.uk

Fatigue of 8090-T8511 Al-Li alloy Al 2.37Li 1.19Cu 0.82Mg 0.11Zr Peak aged - PS = 300 MPa – large extrusion 120 mm by 100 mm Interface between ductile fast fracture (MVC) and fatigue is shown here Original magnification given by micron marker Back to Contents Fractography Resource - mjames@plymouth.ac.uk

Ductile fracture of 8090-T8511 Al-Li alloy Al 2.37Li 1.19Cu 0.82Mg 0.11Zr Peak aged - PS = 300 MPa – large extrusion 120 mm by 100 mm Typical MVC is shown here Original magnification given by micron marker Back to Contents Fractography Resource - mjames@plymouth.ac.uk

Bend Fatigue of 5383-H321 alloy Al 4.43Mg 0.78Mn 0.12Si 0.21Zn 0.09Fe 0.09Cu 0.09Cr Strain hardened – quarter hard - PS = 272 MPa – single pass friction stir welded Crack initiation is from tool travel marks Original magnification given by micron marker Fractography Resource - mjames@plymouth.ac.uk

Bend Fatigue of 5383-H321 alloy Al 4.43Mg 0.78Mn 0.12Si 0.21Zn 0.09Fe 0.09Cu 0.09Cr Strain hardened – quarter hard - PS = 272 MPa – single pass friction stir welded High cycle fatigue shows signs of the underlying microstructure Original magnification given by micron marker Fractography Resource - mjames@plymouth.ac.uk

Bend Fatigue of 5383-H321 alloy Al 4.43Mg 0.78Mn 0.12Si 0.21Zn 0.09Fe 0.09Cu 0.09Cr Strain hardened – quarter hard - PS = 272 MPa – single pass friction stir welded Low cycle fatigue appears more generally ductile striated growth Original magnification given by micron marker Fractography Resource - mjames@plymouth.ac.uk

Bend Fatigue of 5383-H321 alloy Al 4.43Mg 0.78Mn 0.12Si 0.21Zn 0.09Fe 0.09Cu 0.09Cr Strain hardened – quarter hard - PS = 272 MPa – single pass friction stir welded Low cycle fatigue shows clear striations at high magnification Original magnification given by micron marker Fractography Resource - mjames@plymouth.ac.uk

Bend Fatigue of 5383-H321 alloy Al 4.43Mg 0.78Mn 0.12Si 0.21Zn 0.09Fe 0.09Cu 0.09Cr Strain hardened – quarter hard - PS = 272 MPa – single pass friction stir welded SP FSW can lead to partial-fusion defects in the weld nugget (also called 'kissing' bonds) Original magnification given by micron marker Back to Contents Fractography Resource - mjames@plymouth.ac.uk

Ductile Fracture of 5383-H321 alloy Al 4.43Mg 0.78Mn 0.12Si 0.21Zn 0.09Fe 0.09Cu 0.09Cr Strain hardened – quarter hard - PS = 272 MPa – single pass friction stir welded MVC in this alloy Original magnification given by micron marker Back to Contents Fractography Resource - mjames@plymouth.ac.uk

Defects in welded Al-Si-Mg casting alloy Intergranular-interdendritic hot cracking Magnification given by micron marker Back to Contents Fractography Resource - mjames@plymouth.ac.uk

Defects in welded Al-Si-Mg casting alloy Wormhole porosity Magnification given by micron marker Back to Contents Fractography Resource - mjames@plymouth.ac.uk

Defects in welded Al-Si-Mg casting alloy Possible layer porosity Magnification given by micron marker Back to Contents Fractography Resource - mjames@plymouth.ac.uk

Defects in welded Al-Si-Mg casting alloy Illustration of the formation of layer porosity during solidification of an aluminium alloy where the freezing range is large and/or the temperature gradient is low (i.e. solidification occurs over an extended time). Magnification given by micron marker Back to Contents Fractography Resource - mjames@plymouth.ac.uk

Defects in welded Al-Si-Mg casting alloy HC+UC Fatigue crack (F) which has been initiated by a region of hot cracking and undercut/slag inclusion (HC+UC). Magnification given by micron marker Back to Contents F Fractography Resource - mjames@plymouth.ac.uk

Defects in welded Al-Si-Mg casting alloy Increasing the size of the image reveals faint striation-like markings whose spacing indicate a fast growth rate of ~ 1x10-3 mm/cycle of load at this point. Magnification given by micron marker Back to Contents Fractography Resource - mjames@plymouth.ac.uk

Defects in welded Al-Si-Mg casting alloy Illustrative crack growth rate curve for an Al alloy; a crack growth rate of 1x10-3 mm/cycle of load lies in Region III of the curve. Magnification given by micron marker Back to Contents Fractography Resource - mjames@plymouth.ac.uk

Defects in welded Al-Si-Mg casting alloy Parts of both the fatigue and the brittle fracture surfaces, as well as some regions of porosity show the presence of needles, which EDS indicated are likely to be the iron-rich β-phase, Al5FeSi. This phase is known to detrimentally influence the mechanical properties of Al-Si-Mg alloys. Magnification given by micron marker Back to Contents Fractography Resource - mjames@plymouth.ac.uk