The relationship between the nucleation process and thermal hysteresis width in reversible thermoelastic martensitic transformations remains unclear, particularly as the volume of transforming material decreases. Understanding the number density and nature of defects which serve as nucleation sites in this class of materials requires a quantitative analysis of nucleation site potency distributions in different classes of materials with different intrinsic barriers to nucleation. Here, we investigate the size dependence of hysteresis in microscale ${\mathrm{Ni}}_{43}{\mathrm{Co}}_7{\mathrm{Mn}}_{39}{\mathrm{Sn}}_{11}$ alloy particles (radius $4.4\text{–}19.0\mu \mathrm{m}$) during reversible martensitic transformations by collecting temperature-dependent magnetization of 126 individual alloy particles. Size-dependent hysteresis is quantified by a power law model and attributed to friction-induced energy dissipation. In samples with ideal nucleation-limited transformations, martensitic transformation temperatures on cooling decreased with decreasing particle volume due to the low probability of including relatively sparse high-energy nucleation sites. Nucleation site potency distributions are quantified as a function of thermodynamic driving force and compared against potency distributions for thermoelastic martensitic transformations in other classes of materials and for burst martensitic transformations. Across different classes of materials, as the energy barrier associated with the martensitic transformation increases, number densities of defects with sufficient potency to nucleate the transformation decrease dramatically. This finding suggests that very different kinds of defects may be responsible for nucleation of martensitic phase transformations in different material systems.

中文翻译：

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Ni43Co7Mn39Sn11粒子在热弹性马氏体相变中的形核位点势分布

可逆热弹性马氏体转变中成核过程与热滞宽度之间的关系仍然不清楚，特别是随着转变材料体积的减少。要了解这类材料中作为成核位点的缺陷的数量密度和性质，需要对具有不同固有成核壁垒的不同材料类别中的成核位点电位分布进行定量分析。在这里，我们研究磁滞的大小依赖性${你}_{43}{\mathrm{有限公司}}_7{锰}_{39}{锡}_{11}$ 合金颗粒（半径 $4.4\text{–}19.0\mu \mathrm{米}$）在可逆马氏体相变过程中，通过收集126个合金颗粒的温度相关磁化强度。尺寸相关的磁滞通过幂律模型量化，并归因于摩擦引起的能量耗散。在具有理想成核限制相变的样品中，由于包含相对稀疏的高能成核位点的可能性较低，冷却时马氏体相变温度随颗粒体积的减小而降低。将成核位点势能分布作为热力学驱动力的函数进行量化，并与其他类型材料中的热弹性马氏体相变和爆裂马氏体相变的能效分布进行比较。在不同类别的材料中，随着与马氏体相变相关的能垒的增加，具有足以使相变成核的能力的缺陷的数量密度急剧下降。这一发现表明，非常不同种类的缺陷可能是导致不同材料系统中马氏体相变成核的原因。