Aiming at the problem of unstable mechanical properties of the differential pressure casting aluminum alloy long arm parts

the origination was analyzed through the observation of the microstructure and the fracture morphology of the tensile specimen. The results reveal that after refining

modification and grain refinement treatments

the A356 alloy for aluminum alloy long arm parts shows normal microstructure with refined grains

few blowholes and a small amount of oxide inclusions

which have little effect on its instability of mechanical properties. However

with non-proper mold temperature

the porosities are the main cause for the unstable mechanical properties

which appear when the aluminum alloy liquid is solidified and crystallized under absence of feeding pressure at the thicker part of the outermost end of the aluminum alloy long arm.