The mechanical properties and fracture mechanisms of wrought low carbon arc cast (LCAC), molybdenum-0.5pct titanium-0.1pct zirconium (TZM), and oxide dispersion strengthened (ODS) molybdenum flat products
The mechanical properties and fracture mechanisms of wrought low carbon arc cast (LCAC), molybdenum-0.5pct titanium-0.1pct zirconium (TZM), and oxide dispersion strengthened (ODS) molybdenum flat products
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DOI：
10.1016/j.msea.2005.11.030
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发表时间：
2006-02-25
期刊：
影响因子：
6.4
通讯作者：
Cockeram, BV
中科院分区：
文献类型：
--
作者：
Cockeram, BV
钼合金如低碳电弧铸造（LCAC）非合金钼、氧化物弥散强化（ODS）钼和钼-0.5%钛-0.1%锆（TZM）钼对于高温下的结构应用是令人感兴趣的，但是这些合金在缺口存在下的断裂韧性和韧脆转变温度（DBTT）方面的特征很差。在DBTT以上的温度下对这些平轧钼合金进行拉伸和断裂韧性测试，显示出产生韧性层压断裂机制，其中裂纹沿三轴应力区域中的晶界沿着开始，以留下片状晶粒的韧带，其以高度的塑性拉伸至失效。由韧性测试确定的DBTT比由拉伸测试确定的DBTT高50-200 ℃，这显示了缺口的约束效果。J积分试验方法的使用提供了一个更一致和准确的测量断裂韧性值在DBTT以上的温度下观察到大量的塑性。在低于DBTT的温度下，观察到从5.8和29.6 MPa根m之间的韧性值到LCAC的45和175 MPa根m之间的韧性值、TZM的40-215 MPa根m和ODS的53-205 MPa根m之间的韧性值的过渡。在温度> DBTT的断裂韧性值的变化示出与韧性层压特征的尺寸和数量密度相关，其中高断裂韧性值由精细层压间距产生。由于更细的晶粒尺寸导致更小的层压尺寸，因此可以根据韧性层压失效模式来理解细晶粒ODS钼的DBTT较低。(c)2005 Elsevier B. V.保留所有权利。
Molybdenum alloys such as low carbon arc cast (LCAC) unalloyed molybdenum, oxide dispersion strengthened (ODS) molybdenum, and molybdenum-0.5pct titanium-0.1pct zirconium (TZM) molybdenum are of interest for structural applications at high temperatures, but these alloys are poorly characterized with respect to fracture toughness and the ductile to brittle transition temperature (DBTT) in the presence of a notch. Both tensile and fracture toughness testing of these flat rolled molybdenum alloys at temperatures above the DBTT are shown to produce a ductile laminate fracture mechanism, where cracks initiate along grain boundaries in the region of triaxial stresses to leave ligaments of sheet-like grains that are stretched to failure with a high degree of plasticity. The DBTT determined from toughness testing is 50-200 degrees C higher than determined from tensile testing, which shows the constraining effect of the notch. Use of the J-integral test method provided a more consistent and accurate measure of fracture toughness values at temperatures above the DBTT where large amounts of plasticity are observed. A transition was observed from toughness values between 5.8 and 29.6 MPa root m at temperatures below the DBTT to toughness values between 45 and 175 MPa root m for LCAC, 40-215 MPa root m for TZM, and 53-205 MPa root m for ODS. The variation in fracture toughness values at temperatures > DBTT is shown to correlate with size and number density of the ductile laminate features, where high fracture toughness values result from a fine laminate spacing. Since a finer grain size results in a smaller laminate size, the lower DBTT observed for fine grained ODS molybdenum can be understood in terms of the ductile laminate failure mode. (c) 2005 Elsevier B.V. All rights reserved.