In this study, the influences of the grain sizes on the magnesium alloy are investigated to evaluate the friction and wear properties under a dry condition by using a pin-on-disk test machine. Four kinds of ZK60 magnesium alloys with different grain sizes from 6mm to 100mm were used as test specimens and SUJ2 was used for counter materials. It was shown that the wear rate on the small grain size's specimen was increased by the larger plastic deformation near to the worn surface. And, it was also made clear that the coefficient of friction increased due to the influence of adhesive wear in the case of small grain sizes. On the other hand, in the case of large grain size's specimen, the wear-resistance properties increased as compared with the small grain size's specimen because the wear type was an abrasive wear without a plastic deformation. It is appeared that the average coefficient of friction on ZK60 magnesium alloy was about 0.3 in this test condition.
