If the wall thickness is too thin, issues such as plate buckling or local buckling could limit the load capabilities of the structure.

Concentrating all the material close to the center, like in the case of a solid circular rod will increase the critical buckling load of the member.

A thin wall circular hollow section (CHS) is expected to have a high critical buckling load.

A square hollow section (SHS) is inferior in performace in terms of critical buckling load compared to a circular hollow section (CHS) of the same thickness and cross-section area.

Tempering is recommended after the aging process to reduce brittleness.

Can only achieve enhanced mechanical properties if done on Aluminum Alloy and not pure Aluminum.

First, it involved heating till alloy elements fully dissolves in the aluminum and then quenching.

Can achieve enhance mechanical properties if done to pure aluminum.

Surface needs to be shot peened to produce a layer with residual compressive stresses.

Part will also require quenching to achieve a hardened surface.

Part are soaked in a carbon rich environment at elevated temperatures for a significant amount of time to allow the carbon to seep into the surface resulting in the surface regions with a higher carbon concentration.

Case hardening will only be effective if the entire part is made of medium or high carbon steel.

Mild steel/Low carbon steel is the preferred cost effective option for case hardened parts.

Annealed the material. i.e. heat till around 500"C~650"C and hold for several hours until the crystal reform and grow, forming large crystals.

Cold working or work hardening the material by introducing permanent deformation at room temperature.

Heat up workpiece till forging temperature (950"C~1250"C) and hold long enough till material converts to austenite and then quench (cool rapidly) in oil or water.

Decrease the crystal grain size via forging or hot rolling.

Age  the material by storing in a cool dry cellar for several months.