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采用对比试验方法,研究加钛和加钛方式对活塞合金ZL108疲劳裂纹扩展性能的影响。分别以电解低钛铝基合金和Al-5.3%Ti中间合金为基,熔配与ZL108合金成分基本相同的两种加钛的ZL108合金,分别记为ZL108D和ZL108R,测试三种合金的疲劳裂纹扩展速率da/dN和门槛值ΔKth。运用数据代表点拟合的新方法处理同组试样的疲劳裂纹扩展试验数据,结果表明:相对ZL108合金而言,ZL108D和ZL108R合金具有更高的抗疲劳裂纹扩展能力。两种加钛合金抗疲劳裂纹扩展性能有所提高的主要原因在于钛的细化作用,使α(Al)晶粒二次枝晶间距变小,硅颗粒分布更加均匀,圆形度提高且平均直径变小,微观上增加了疲劳裂纹扩展的阻力。而两种加钛方式的影响则差别不大。
The effects of titanium and titanium addition on the fatigue crack propagation of ZL108 piston were studied by comparative test. Two kinds of titanium-added ZL108 alloys with the same composition as ZL108 alloy were respectively melted by electrolysis of low-titanium aluminum alloy and Al-5.3% Ti master alloy respectively and recorded as ZL108D and ZL108R respectively. The fatigue cracks of the three alloys were tested Expansion rate da / dN and threshold ΔKth. Fatigue crack growth test data of the same group of samples were processed by a new method of data representative point fitting. The results show that ZL108D and ZL108R alloys have higher fatigue crack propagation resistance than ZL108 alloy. The main reason for the increase of fatigue crack growth resistance of the two kinds of titanium alloys is that the thinning effect of titanium reduces the secondary dendritic spacing of α (Al) grains, the distribution of silicon particles is more uniform, the circularity is improved and the average The smaller the diameter, the microscopic increase the fatigue crack growth resistance. The effect of the two plus titanium method is not very different.