Abstract:
Al alloys play important role in modern engineering applications due to low density, functional
strength, and corrosion resistance because of the corrosion inhibiting oxide layer. Al-alloys are
now being a major part where high strength and thermal stability is required. High-temperature
Al alloys are widely used in automotive and aerospace applications like piston, cylindrical head,
and rotor. In such kind of situation, it will be exposed to a high temperature for a long period.
Al-alloys, for high temperature, need to have thermal stability and maintain their strength while
used at a temperature around 2000
C and above. The loss of strength at high temperatures occurs
due coarsening of precipitates. To overcome these effects non-equilibrium solidification route
can be used, where it is likely to bring precipitates, which can play vital role in inhibiting
coarsening. This research studies the microstructural and mechanical properties of Al alloy with
the addition of a small amount of Co, Sc and Zr prepared through vacuum suction cast, which
can provide rapid solidification. This research is done on Al-0.1Co, Al-0.2Co, and Al-0.3Co.
When Co amount added is increasing there is a direct increment in Vickers microhardness due
to a direct increase of Al9Co2 intermetallic. 0.15Sc and 0.15Zr were added to Al-Co alloys that
can provide precipitation strengthening under heat treatment. It is seen that Zr and Sc assist
strongly in the refinement of the grain because after the addition of Zr and Sc the grain of Al-Co
turned from columnar elongated to equiaxed one. Grain boundry segregation of Co was
observed. Samples were exposed to Direct aging at 3750
C and 4500
C. The Al-0.1Co-0.15(ScZr)
has higher hardness than Al-0.2Co-0.15(ScZr) and Al-0.3Co-0.15(ScZr) in both cases aged at
3750
C and 4500
C which is 835MPa and 667.66MPa respectively. When samples go direct aging
the smaller amount of Co provide higher microhardness and thermal stability cause it is less
prone to intergranular fracture due to less grain boundary segregation. The average
4th Nov, 2020 iv
microhardness obtained is 835MPa for direct aged Al-0.1Co-0.15(ScZr) and 799.9MPa after
exposure to 2000
C for 200hr
