High strength NiTiHf shape memory alloys with tailorable properties
High strength NiTiHf shape memory alloys with tailorable properties
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DOI：
10.1016/j.actamat.2017.05.065
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发表时间：
2017-08
期刊：
影响因子：
9.4
通讯作者：
S. Saghaian;H. Karaca;H. Tobe;A. S. Turabi;S. Saedi;S. Saghaian;Y. Chumlyakov;R. Noebe
中科院分区：
文献类型：
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作者：
S. Saghaian;H. Karaca;H. Tobe;A. S. Turabi;S. Saedi;S. Saghaian;Y. Chumlyakov;R. Noebe
NiTiHf形状记忆合金的微观结构可以设计成具有高强度和在大温度窗下的高应力水平下工作。纳米沉淀是一种众所周知的提高材料强度的方法，但它可以用于NiTiHf合金，从而大大改变其相变特性（马氏体形貌、相变应变、滞后和应力）。富镍ni51.2 ti28.8 hf20在固溶处理（900°C-3h/水淬）和低温时效后的马氏体相变受到严重抑制，而在650°C-3h时效后的马氏体相变温度大于100°C。在450°C和550°C时效3小时后，产生纳米尺寸的析出物（尺寸约为20 nm），提高了材料的强度，在大于1500 MPa的应力水平下，在等压热循环期间具有接近完美的尺寸稳定性，输出功为20 - 30 J cm−3。在450°C-3h时效后的低温（- 20 ~ 40°C）和550°C-3h时效后的高温（120 ~ 160°C）下，均表现出4%可恢复应变的超弹性行为，应力达到2 GPa而未发生塑性变形。热处理、微观结构、力学和形状记忆性能之间的明确关系将被显示出来。
Microstructure of NiTiHf shape memory alloys can be engineered to have high strength and operate at high stress levels for a large temperature window. Nanoprecipitation is well-known method to improve the strength of materials but it can be employed to NiTiHf alloys to substantially alter their phase transformation characteristics (martensite morphology, transformation strain, hysteresis and stress). The martensitic transformation of Ni-rich Ni51.2Ti28.8Hf20was severely suppressed in the solution treated condition (900 °C-3h/water quench) and after aging at low temperatures, while the transformation temperatures were greater than 100 °C after 650 °C-3h aging. Generation of nanosize precipitates (∼20 nm in size) after 3 h aging at 450 °C and 550 °C improved the strength of the material, resulting in a near perfect dimensional stability during isobaric thermal cycling at stress levels of greater than 1500 MPa, with work output of 20–30 J cm−3. Superelastic behavior with 4% recoverable strain was demonstrated at low temperatures (−20 to 40 °C) after aging at 450 °C-3h and at elevated temperatures (120–160 °C) after aging at 550 °C-3h, with stresses reaching 2 GPa without the onset of plastic deformation. A clear relationship between thermal treatments, microstructure, mechanical and shape memory properties will be shown.