The local structures of mechanically alloyed Cu-Sn mixtures have been investigated by X-ray absorption fine structure (XAFS) technique. The result indicates that the bond length of the Cu-Cu first shell slightly increases and the coordination number of the Cu-Sn first shell largely increases with the milling times for the Cu-Sn alloys. This means that the inter-diffusion between Cu and Sn grains

driven by mechanical alloying

results in forming Cu-Sn alloy. After milling 4h

the coordination number and the bond length of the Cu-Cu first shell change from 12 to 7.4 and from 2.55 ?to 2.60 ?for the Cu-Sn alloys

respectively. After 12h milling

the coordination number of the Cu-Cu first shell decreases to 6.4 while that of the Cu-Sn first shell increases to 5.1 and its bond length is about 2.80 for the Cu-Sn alloy. Furthermore

the XAFS result for the Cu-Sn alloy milled for 72 h is similar to that for 12 h. This implies that the inter-diffusion between Cu and Sn grains has nearly reached the equilibrium and an amorphous Cu-Sn alloy of Cu6Sn5-like is formed.