【作者】 刘文才；

【导师】 翁永刚；

【作者基本信息】 郑州大学 ， 材料物理与化学， 2006， 硕士

【摘要】 ZL108合金是一种常用的活塞合金，国家标准中并没有要求含钛元素。为系统地研究加钛和不同的加钛方式对ZL108合金疲劳性能和断裂韧性的影响，以电解低钛铝基合金和A1-Ti中间合金为原材料，采用相同的试验条件，分别制备ZL108合金、电解加钛ZL108合金（记作ZL108D）和熔配加钛ZL108合金（记作ZL108R），在MTS810型材料试验机上进行对比试验。 在疲劳裂纹扩展试验中测量了三组合金的疲劳裂纹扩展速率和门槛值。基于同组合金各试样对该合金的da／dN-△K曲线贡献应相等，提出了成组试验数据代表点拟合的新方法，用不同试样的试验数据代表点拟合出该合金Paris公式的单一组参数C和m，以便于不同组合金试验结果的比较。 研究发现，两种加钛方式都提高了ZL108合金的门槛值△K_th，并且ZL108D的门槛值高于ZL108R合金。在不同疲劳裂纹扩展阶段，电解加钛和熔配加钛对扩展速率da／dN的影响有所不同。在近门槛区，两种加钛合金的扩展速率显著低于ZL108合金，ZL108D合金的扩展速率最低；而在Paris区，三种合金的疲劳裂纹扩展速率变化趋势与近门槛值区相同，但差别没有近门槛值区明显。 在断裂韧性试验中测量了三组合金的平面应变断裂韧度K_IC，采用数理统计中显著性检验方法分析试验数据。结果表明，在显著度2％水平，加钛提高了ZL108合金的平面应变断裂韧度K_IC，两种加钛方式相互间没有大的区别。 微观分析表明，向ZL108合金中加入Ti元素，可以细化α（Al）相的尺寸，使一次枝晶变短，二次枝晶间距减小；同时增强了合金中Sr的变质效果，使共晶硅颗粒分布更加均匀，平均直径变小且圆形度提高；并改善Fe相存在形态，从而提高了ZL108合金抗疲劳裂纹扩展能力和断裂韧性。更多还原

【Abstract】 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 ΔK_th of alloy ZL108 is increased in the two titanium alloying methods, and the threshold ΔK_th 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 K_IC of three alloys are measured in fracture toughness test, and the data are analyzed by the statistical significance test. The results更多还原