Fatigue crack propagation behavior in commercial purity Ti severely deformed by accumulative roll bonding process
Fatigue crack propagation behavior in commercial purity Ti severely deformed by accumulative roll bonding process
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DOI：
10.2320/matertrans.me200716
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发表时间：
2008-01-01
影响因子：
1.2
通讯作者：
Tonda, Hideki
中科院分区：
文献类型：
--
作者：
Kitahara, Hiromoto;Uchikado, Kosuke;Tonda, Hideki
研究了累积叠轧复合（ARB）工艺大变形工业纯钛板的疲劳性能。ARB过程进行了多达6个循环（等效应变，ε（eq）= 4.8）。经2、4和6次循环处理后的板材由细小的等轴晶和拉长的片层晶组成。在6次循环的ARB板材中，细小等轴晶的平均尺寸为89 nm，片层晶的平均厚度为67 nm。拉伸强度随着ARB循环次数的增加而增加。进行疲劳裂纹扩展试验，以阐明疲劳性能，如裂纹扩展速率和裂纹扩展的阈值应力强度因子范围（Δ K-th）。ARB处理的样本的Δ K-th小于起始片材的Δ K-th。Δ K-th随着ARB循环次数的增加而减小，直到4个循环。然而，6次循环试样的Δ K-th大于4次循环试样的Δ K-th。6次循环试样的断裂表面与2次循环和4次循环试样的断裂表面不同。疲劳裂纹扩展行为在4周和6周试样之间变化。另一方面，裂纹扩展速率随着ARB循环次数的增加而减小。
Fatigue properties of commercial purity titanium sheets severely deformed by the accumulative roll bonding (ARB) process were investigated. The ARB process was carried out up to 6 cycles (equivalent strain, epsilon(eq) = 4.8). The sheets ARB processed by 2-, 4- and 6-cycle consist of fine equiaxed grains and elongated lamellar grains. In the sheet ARB processed by 6-cycle, the mean size of fine equiaxed grain was 89 nm, and the mean thickness of the lamellar grains were 67 nm. The tensile strength increased with increasing the number of the ARB cycle. Fatigue crack growth tests were performed to clarify the fatigue properties such as the crack growth rate and threshold stress intensity factor range for crack growth (Delta K-th). The Delta K-th of the ARB processed specimens were smaller than that of the starting sheet. The Delta K-th decreased with increasing the number of the ARB cycle until 4-cycle. However, the Delta K-th of 6-cycle specimen was larger than that of the 4-cycle specimen. Fracture surface of the 6-cycle specimen was different from that of the 2- and 4-cycle specimens. Fatigue crack propagation behavior changes between 4- and 6-cycle specimens. On the other hand, the crack growth rate decreases with increasing the number of the ARB cycle.