Abstract:
This work deliberates the influence of ageing on Mechanical and Fatigue properties of
Aluminium alloy 2014T6. In addition, the influence of ageing on micro-structure is also
considered using Optical Microscopy, Scanning Electron Microscope (SEM) and X-ray
Diffraction. Experiment begins with solution treatment to the as received Aluminium
alloy 2014 T6 (industrial available) at temperature 504°C. Solution treatment restore
any microstructure alterations present. Quenching followed by solution treatment locks
the microstructure of AA2014 in Super saturated meta-stable state. Subsequently,
ageing treatment was completed at three different temperatures and four different time
periods. No significant variations detected in mechanical and fatigue properties for
ageing temperature of 130°C. however a decent hike was observed for ageing at
temperature 160°C. The raise was continuous up to 10Hour of time period. Ultimate
Tensile Strength and Yield Strength for this ageing parameter was 490MPa and
440MPa with an increase of about 35% and 50% respectively. An increase in fatigue
behaviour was also observed till 8Hour of ageing after that a deleterious effect was
noted. However, ageing has a deleterious effect on material elongation properties.
Exploring microstructure with different tricks shows nucleation and growth of different
phases while ageing of alloy. SEM, EDX and XRD plots of differently aged samples
discloses that as the number and size of the phases increases the material strength
increases too. Examining the crack through Optical and SEM reveals the deviation of
crack path from straight line to zig-zag along with ageing. Investigations concerning
crack path reveals that zig-zag path are the mark of increase in fatigue resistance. The
deviations are due to the presence of hard phases nucleated during ageing. Ageing at
190°C shows increase in material strength for a while later on it has a deleterious effect
on mechanical properties. This may be a result of over ageing of the alloy. The number
and sizes of the phases present in these cases are relatively larger than 160°C ageing.
