Abstract:

          We analyzed early fracture cause for the combination rib in a change wheel of ADC14 aluminium alloy with chemical composition analysis, SEM observation and metallographic examination. Results show that inhomogeneous distribution of thick massive primary silicon, intergranular distribution of massive brittle phase, acicular brittle iron phase and more casting defects of porosities in the matrix can make the plasticity reduction and the brittleness increase, and further cause early brittle fracture of the rib. We therefore present the improved methods for casting technique.

Key words: aluminium alloy, change wheel, shrinkage porosity, brittle phase, early brittle fracture