Effect of Forging Ratio and Grain Size on Tensile and Fatigue Strength of Pure Titanium Forgings
Effect of Forging Ratio and Grain Size on Tensile and Fatigue Strength of Pure Titanium Forgings
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DOI：
10.2472/jsms.54.66
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
Yuki Kobayashi;Yoshiteru Tanaka;K. Matsuoka;K. Kinoshita;Y. Miyamoto;H. Murata
中科院分区：
文献类型：
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作者：
Yuki Kobayashi;Yoshiteru Tanaka;K. Matsuoka;K. Kinoshita;Y. Miyamoto;H. Murata
纯钛具有耐腐蚀、比强度高、可降低拆船成本、可回收等优点，有望在高速船舶上得到应用。钛制舵锻件是舵板和舵柄的整体组合，已用于高速船舶。舵柄上经常观察到疲劳断裂。在这些断裂的背景下，使用锻造比为2和4、不同晶粒尺寸的锻件进行了拉伸和疲劳试验。得到的典型结果总结如下：(1)拉伸试验中0.2%的证明应力符合Hall-Petch方程；(2)其斜率与低碳钢近似相等；(3) S-N曲线表明，锻造比为4的锻件的疲劳强度明显优于锻造比为2的锻件；(4)在大晶粒之间的晶界处观察到疲劳裂纹萌生，表明疲劳强度的降低是由非均匀组织引起的；(5)锻造比对疲劳强度的影响明显，对拉伸性能的影响较小。
Pure titanium is expected to be used in high-speed ships in light of its corrosion resistance, high specific strength, ability to reduce ship-dismantling costs, and recyclability. Titanium rudder forgings, each of which is an integrated combination of a rudder plate and a rudder stock, have been used for high-speed ships. Fatigue fractures have often been observed in the rudder stocks. In the context of these fractures, tensile and fatigue tests were performed using forgings with forging ratios of 2 and 4 and different grain sizes. Typical results obtained are summarized as follows : (1) 0.2% proof stresses in the tensile test agreed with the Hall-Petch equation; (2) their slope was approximately equal to that for low-carbon steels ; (3) S-N curves showed that forgings with a forging ratio of 4 were obviously superior in fatigue strength to those with a forging ratio of 2 ; (4) fatigue crack initiation was observed at grain boundaries between large grains, indicating that the decrease in fatigue strength is caused by an inhomogeneous microstructure; and (5) the forging ratio had an obvious effect on fatigue strength rather than on tensile properties.