论文部分内容阅读
局部包套压缩大塑性变形能够实现镍钛形状记忆合金的完全非晶化,其中少量残留的纳米晶相分布在非晶基体上。研究非晶镍钛合金在573、723和873 K退火条件下的晶化机制。采用约翰逊-迈尔方程描述非晶镍钛合金的晶化动力学行为。在573和723 K的退火条件下,可以获得具有完全纳米晶相的镍钛形状记忆合金,在该纳米晶镍钛形状记忆合金中,马氏体相变由于晶界的约束而受到了抑制。在873 K的退火条件下,非晶镍钛合金的晶化产生了晶粒粗大的镍钛形状记忆合金样品。在室温条件下的粗晶镍钛样品中,可以观察到马氏体复合孪晶,而且发现马氏体孪晶在晶界优先形核,并且向两个不同的晶粒内部长大。局部包套压缩大塑性变形结合后续退火工艺为制备纳米晶镍钛形状记忆合金提供了一种新的途径。
The local plastic deformation of the enveloping can realize complete amorphization of NiTi shape memory alloy, in which a small amount of residual nanocrystalline phase is distributed on the amorphous matrix. The crystallization mechanism of amorphous nickel-titanium alloy at annealing temperature of 573, 723 and 873 K was studied. Crystallization kinetics of amorphous nickel-titanium alloy was described by Johnson-Meyer equation. Under annealing conditions of 573 and 723 K, a nickel-titanium shape memory alloy with a complete nanocrystalline phase can be obtained in which the martensitic transformation is suppressed due to the grain boundary constraints. Crystallization of the amorphous nickel-titanium alloy resulted in coarse grain NiTi shape memory alloy samples at 873 K annealing conditions. In the coarse-grained nickel-titanium samples at room temperature, martensite twinning was observed, and martensite twins were found to preferentially nucleate at the grain boundaries and grow inside two distinct grains. Local plastic shrinkage compression combined with the subsequent annealing process for the preparation of nanocrystalline NiTi shape memory alloy provides a new way.