Keywords: Ultrafine grained Aluminium nano composite sheet, stir casting and cryo-rolling,
strength and ductility, thermal stability, crystallographic texture, forming limit diagram, bend
fracture limit, roll forming
Aluminium and its alloys (Al) have huge potential in automobile and aerospace industries due
to their significant light weighting ability along with several advantages such as good anti-rust
properties, better corrosion resistance and low cost. But, these alloys often show low to
moderate strength. Al matrix nano composites and ultrafine grained Al show excellent
mechanical properties in their individual level. In order to gain the benefit of both types of
materials, in the present work, novel ultrafine grained (UFG) Al matrix nano-composite sheets
with varying reinforcement content were developed by an innovative cryogenic deformation
based hybrid manufacturing route. The process also eliminated the drawbacks of the existing
manufacturing routes which are limited to produce small scale components. Another limitation
such as the agglomerations of the nano particles was eliminated by multi-pass cryo-rolling with
90% thickness reduction. The presence of nano particles led to an increased accumulation of
dislocations in the matrix and improved strength but reduced ductility. The addition of 0.5 and
1 wt% nano particles increased the yield strength of the nano composites by 42% and 48%
respectively, whereas further increase in reinforcement content impaired the mechanical
properties due to nano particle agglomeration. The microstructural information and the
obtained theoretical and experimental yield strengths of the UFG nano composites were
validated with implemented mathematical modelling results. In order to improve the ductility,
the materials were then subjected to annealing treatments at different temperatures. At high
annealing temperature, nano particles restricted the grain growth resulting higher activation
energy for grain growth in the composite (~198 kJ/mol) compared to the unreinforced UFG Al
(~166 kJ/mol). The microstructural evolutions and crystallographic textures were studied using
microscopy and compared with the respective mechanical properties evaluated with uniaxial
tensile tests. The sub-micron (