| Alloy ZL108 is used for piston materials widely; it is not needed to contain titanium for ZL108 according to the national standard now. In order to study the effects of element titanium and different titanium alloying methods on the fatigue properties and fracture toughness of alloy ZL108 systematically, the electrolytic low titanium alloying ZL108 (referred as ZL108D) and the low titanium alloying ZL108 by melting (refer as ZL108R) are made from electrolytic low-titanium aluminum base alloy and Al-Ti master alloy respectively, which are undergone the same test conditions. Together with the alloy ZL108 containing no titanium, these three kinds of alloy ZL108 specimens are tested for comparison on the MTS810 material test system.Parameters of the fatigue crack growth rate and the threshold AK,h are measured in the fatigue crack growth test. It is convinced that every specimen of the same group should contribute equally to its da/dN-ΔK curve. A new data processing method, named as the representative points simulating method for group data of different specimens, is proposed for getting the single group parameters C and m of Paris formula.The test results show that the threshold ΔKth of alloy ZL108 is increased in the two titanium alloying methods, and the threshold ΔKth of ZL108D is higher than that of ZL108R. The effects of the two titanium alloying methods on fatigue crack growth rate are different in different test procedure. Near the threshold, fatigue crack growth rates of two alloys containing titanium are lower than that of ZL108 alloy apparently, and the rate of alloy ZL108D is the least. The variation trend of fatigue crack growth rates of three alloys in Paris zone is similar to that in threshold zone, but is not as obvious as near threshold zone.The plane-strain fracture toughness KIC of three alloys are measured in fracture toughness test, and the data are analyzed by the statistical significance test. The results...
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