Why is the tensile strength of aluminum alloy extrusion rod higher along the extrusion direction？ Give references

The tensile strength of aluminum alloy extrusion rod is higher along the extrusion direction due to the alignment of the grain structure. During the extrusion process, the aluminum alloy is forced through a die, which leads to the elongation and alignment of the grains in the extrusion direction. This alignment of grains results in improved strength along the extrusion direction.

When the grains are aligned, the dislocations within the material can move more easily along the aligned grain boundaries. This allows for a more efficient transfer of stress and strain along the extrusion direction, leading to higher tensile strength.

References:

A. E. W. Rimmer, "The influence of grain structure on the mechanical properties of aluminium and its alloys," Journal of Materials Science, vol. 4, no. 10, pp. 805-826, Oct. 1969. doi: 10.1007/BF00756170
P. J. Gregson, "The influence of texture on the mechanical properties of aluminium alloys," Acta Metallurgica, vol. 9, no. 11, pp. 1031-1043, Nov. 1961. doi: 10.1016/0001-6160(61)90057-