The effects of silicon particle content and testing temperature on friction and wear properties of casting in-situ silicon particle reinforced ZA27 composites were investigated.The wear mechanisms were mainly discussed by observations of both worn surfaces and their side views.The results indicated that the variations of wear resistance with increasing of silicon particle content,at all of the testing temperatures applied,showed a similar tendency with a manner of non-monotonous change.It was surprised that the wear resistance decreased with the increase of silicon particle content from 2 vol.%to 5 vol.%,while it increased when the content was less than 2 vol.%or more than 5 vol.%.Similarly,the friction coefficient also did not change monotonously.The dominative wear mechanism changed from a relatively severe regime of plastic deformation accompanied by adhesion wear to a mild regime of smear,then to a very severe regime of severe plastic deformation induced wear,and finally again to a relatively mild regime of smear accompanied by abrasive wear as the silicon content increased.The wear resistance always decreased with elevating testing temperature,but the decrease ranges were different for the composites with different silicon contents.The friction coefficients changed irregularly for the different composites with the increase of testing temperature.Correspondingly,the wear mechanism alternated from a mild regime of smear accompanied by abrasive wear to a severe regime of plastic deformation accompanied by adhesion wear. The effects of silicon particle content and testing temperature on friction and wear properties of casting in-situ silicon particle reinforced ZA27 composites were investigated. The wear mechanisms were mainly discussed by observations of both worn surfaces and their side views. The results indicated that the variations of wear resistance with increasing of silicon particle content, at all of the testing temperatures applied, showed a similar tendency with a manner of non-monotonous change. It was surprised that the wear resistance decreased with the increase of silicon particle content from 2 vol. % to 5 vol.%, while it increased when the content was less than 2 vol.% or more than 5 vol.%. Similarly, the friction coefficient also did not change monotonously.The dominative wear mechanism changed from a relatively severe regime of plastic deformation accompanied by adhesion wear to a mild regime of smear, then to a very severe regime of severe plastic deformation induced wear, and finally again to a relatively mild regime of smear accompanied by abrasive wear as the silicon content increased. wear resistance always decreased with elevating testing temperature, but the decrease ranges were different for the composites with different silicon contents. the friction coefficients changed irregularly for the different composites with the increase of testing temperature. Correspondingly, the wear mechanism alternated from a mild regime of smear accompanied by abrasive wear to a severe regime of plastic deformation accompanied by adhesion wear.