Shock-induced martensitic transformations in near-equiatomic NiTi alloys
Shock-induced martensitic transformations in near-equiatomic NiTi alloys
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DOI：
10.1007/s11661-997-0207-2
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发表时间：
1997-07
期刊：
影响因子：
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通讯作者：
A. Thakur;N. Thadhani;R. Schwarz
中科院分区：
文献类型：
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作者：
A. Thakur;N. Thadhani;R. Schwarz
利用冲击产生的拉伸应力脉冲诱导两种具有不同马氏体转变起始温度（Ms）的近等原子NiTi合金的b2向单斜马氏体转变。NiTi-I合金（Ms≈+27℃）在室温下以2.0和2.7 GPa的脉冲拉伸应力冲击，呈现针状马氏体形态。这些马氏体针具有含有微孪晶的亚结构，是典型的“应力辅助”马氏体。在2 GPa的拉伸应力脉冲下，NiTi-II合金（Ms≈−45℃）未形成马氏体。当拉伸应力为4.1 GPa时，合金在最大拉伸应力持续时间附近出现了片状萌生。此外，单斜马氏体针在小片区域周围聚集，具有明确的位错亚结构，是典型的“应变诱导”马氏体。该合金温度极低，未形成应力辅助马氏体。本文记录了使用冶金技术产生有限持续时间的大振幅拉伸应力脉冲的结果，用于研究涉及从高密度到低密度状态变化的相变。
Shock-impact generated tensile-stress pulses were used to induce B2-to-monoclinic martensitic transformations in two near-equiatomic NiTi alloys having different martensite transformation start (Ms) temperatures. The NiTi-I alloy (Ms≈+27 °C) impacted at room temperature at 2.0 and 2.7 GPa tensile stress-pulse magnitude, showed acicular martensite morphology. These martensite needles had a substructure containing microtwins, typical of “stress-assisted” martensite. The NiTi-II alloy (Ms≈−45 °C) showed no martensite formation when shocked with tensile-stress pulses of 2 GPa. For tensile stresses of 4.1 GPa, the alloy showed spall initiation near the region of maximum tensile-stress duration. In addition, monoclinic martensite needles, with a well-defined dislocation substructure, typical of “strain-induced” martensite, were seen clustering around the spall region. No stress-assisted martensite was formed in this alloy due to its very lowMstemperature. The present article documents results of the use of a metallurgical technique for generating large-amplitude tensile stress pulses of finite duration for studies of phase transformations involving changes from a high density to a low density state.