Abstract Heusler alloys demonstrate various effects, such as the ferromagnetic shape memory effect, the magnetocaloric effect, etc. But these alloys are also liable to destruction during multiple cycles of martensitic transformation. In order to increase stability of functional properties of the alloys, thermo-mechanical treatment by various methods is carried out. In this work, a Heusler Ni2.26Mn0.80Ga0.89Si0.05 alloy was subjected to combined deformation processing: multiple isothermal forging and subsequent direct extrusion. The multiple isothermal forging was carried out at 700 °C in 5 upset transitions and a total true degree of deformation of e ≈ 2.42. The extrusion was also carried out at 700 °C with an extrusion ratio of 2:1 (e = 1.39). Analysis of the microstructure shows that, resulting from combined treatment, metallographic and crystallographic textures are formed. The metallographic texture is characterized by coarse grains of approximately 1 mm in length and hundreds of microns in diameter. The coarse grains are in turn surrounded by a layer of fine-grained structure. The crystallographic texture is axial of the 〈1 1 0〉 type. This kind of structure enhances mechanical properties of the alloy. According to the study of thermal expansion anisotropy in the region of martensitic transformation, contribution of the martensitic transformation to the relative change in the length of the extruded sample is 0.13% in the direction, normal to the extrusion axis, and 0.09% - along it. These values are comparable to those observed on Heusler alloys in the as-cast state. Thus, it is found that thermo-mechanical treatment by the combined method allows obtaining a significant amount of thermal expansion anisotropy while remarkably increasing mechanical properties of the material.

中文翻译：

---

Ni2.26Mn0.80Ga0.89Si0.05合金挤压形成的热膨胀各向异性

摘要 赫斯勒合金表现出多种效应，如铁磁形状记忆效应、磁热效应等。但这些合金在多次马氏体相变过程中也容易被破坏。为了增加合金功能性能的稳定性，通过各种方法进行热机械处理。在这项工作中，对 Heusler Ni2.26Mn0.80Ga0.89Si0.05 合金进行了组合变形加工：多次等温锻造和随后的直接挤压。多次等温锻造在 700 °C 下进行 5 次镦锻过渡，总真实变形度 e ≈ 2.42。挤出也在 700 °C 下进行，挤出比为 2:1 (e = 1.39)。微观结构分析表明，由于联合处理，形成金相和晶体结构。金相组织的特征是长约1毫米、直径数百微米的粗晶粒。粗晶粒依次被一层细晶粒结构包围。晶体结构是<1 1 0> 型的轴向结构。这种结构提高了合金的机械性能。根据对马氏体相变区域热膨胀各向异性的研究，马氏体相变对挤压试样长度相对变化的贡献在垂直于挤压轴的方向上为0.13%，沿挤压轴为0.09% . 这些值与在铸态的 Heusler 合金上观察到的值相当。因此，