Investigation On Mechanical And Wear Properties Of Alloy ZL108 Prepared With Electrolytic Low-Titanium Aluminum Base Alloy

Alloy ZL108 is a main brand of cast aluminum alloy used for engine piston materials, it is not needed to contain titanium according to the national standard now. Three kinds of ZL108 alloys were produced under the same technology of melting, heat treatment and machining. One is the normal alloy ZL108 containing no titanium; the second is produced with the electrolytic low-titanium aluminum base alloy (referred as ZL108D); the third is produced with pure aluminum and Al-Ti master alloy (referred as ZL108R). The influences of lower Ti alloying and different titanium alloying methods on the mechanical and wear properties of alloy ZL108 are studied in the comparative tests. At last, the microstructures and wear-surface morphologies are also investigated by contrast methods.The results of room temperature tensile tests show that both methods of electrolytic aluminum alloying and titanium alloying by melting can improve the mechanical properties of ZL108 alloy, while the yield strength and hardness of ZL108D are superior to ZL108R. The microstructure analysis reveals that the grains of alloy ZL108 are refined obviously by titanium. The primary dendrite length and the second dendrite spacing of a(Al) get shorter, and the average diameter of eutectic silicon particles decreases while the roundness increases. And the refining effect of electrolytic titanium alloying method is better than that of melting method.The results of tensile tests at 350℃ show that tensile properties of ZL108 alloy are not improved obviously, probably because grain-boundary strength has declined greatly.The analysis of the wear-surface morphologies shows that abrasive wear and delamination wear are the main wear mechanism under dry friction, and abrasive wear is the main wear mechanism under lubricant friction. The investigation indicates that both electrolytic titanium alloying method and titanium alloying method by melting can improve the wear resistance of alloy ZL108 under dry or lubricant friction, while...