Abstract: The effect of quenching temperature on the two internal friction peaks in a Cu-11.9Al-2.5Mn (wt%) shape memory alloy during heating was studied by using a low frequency inverted torsion pendulum internal friction instrument.It was demonstrated that the high-temperature peak aroise from the reversible martensitic transformation while the low-temperature peak from the refinement of twins.The low-temperature peak rose with increasing quench temperature because relatively high quench temperature produced relatively coarse twins whith were favorable for the sliding motion of the twins.The high-temperature peak reached its maximium at 700 ℃ and thereafter it declined as the quench temperature increased due to quench induced defect population.