Abstract :
The metal foundry industry is growing along with the development of
casting techniques and methods as well as various models of cast products that are
flooding the domestic market. Cast products are widely used in daily life from
household furniture, automotive parts, ships, to airplanes.
This casting uses aluminum alloys derived from used aluminum-based
propellers. With high variations of sprue used are: 50 mm, 100 mm, and 150 mm.
This test aims to determine the effect of high sprue variation on tensile strength,
hardness, and micro structure. Cast aluminum is tensile tested according to ASTM E8
/ E8M-09 standard and hardness values using Vickers hard test apparatus with
diamond pyramid indentors weighing 150 Kg.
The test results showed that the largest tensile strength was 21.86 Kgf /
mm2 on a high sprue variation of 150 mm and the lowest tensile strength was 18.15
Kgf / mm2 on a high sprue variation of 100 mm. Meanwhile, the cast product on
aluminum alloy based propeller used has the greatest hardness of 82.2 HV on high
sprue variation of 150 mm and the lowest hardness is 71,10 HV without using sprue
height. The analysis is supplemented by microstructural observations. In the
observation results obtained the conclusion that the higher the sprue the more solid
precipitate and soft particles.