A grain-size gradient NiTi ribbon with multiple-step shape transition was papered by means of melt-spinning. The ribbons contain coarse and fine grains in the free surface side and copper roller surface side, respectively. The grain-size gradient microstructure induces a two-stage phase transformation behavior in the ribbons during heating or cooling. After tensile deformation pre-treatment, the ribbons exhibit a back-and-forth shape change (shape A→B→A) upon a single heating or cooling process, resulting from the sequential phase transformation through the thickness of the ribbon as dictated by gradient grain size. The activating performance of the ribbons, i.e. shape transition amplitude and speed, can be customized by controlling the pre-deformation strain. This work offers a new opportunity for innovative designs to reach a novel shape memory behavior in NiTi alloys conveniently and efficiently.

通过熔融纺丝对具有多步形状转变的粒度梯度NiTi带进行了纸化。这些带分别在自由表面侧和铜辊表面侧包含粗大颗粒和细小颗粒。晶粒尺寸梯度微结构在加热或冷却过程中引起带中的两阶段相变行为。经过拉伸变形预处理后，碳带在一次加热或冷却过程中会出现来回的形状变化（形状A→B→A），这是由梯度决定的碳带厚度的相继相变导致的晶粒尺寸。可以通过控制预变形应变来定制带的激活性能，即形状过渡幅度和速度。