Large cyclic deformation of a Ni-Mn-Ga shape memory alloy induced by magnetic fields
Large cyclic deformation of a Ni-Mn-Ga shape memory alloy induced by magnetic fields
复制标题
DOI：
10.1063/1.1513875
复制
发表时间：
2002-11
影响因子：
3.2
通讯作者：
P. Müllner;V. Chernenko;M. Wollgarten;G. Kostorz
中科院分区：
文献类型：
--
作者：
P. Müllner;V. Chernenko;M. Wollgarten;G. Kostorz
对单晶Ni-Mn-Ga铁磁性形状记忆试件进行了马氏体态的单轴压缩变形，总应变为2%。应力-应变曲线显示屈服点在6 Mpa处，然后是急流。在机械变形后，进行了恒强旋转磁场中的磁力试验和变强度恒向磁场中的磁力试验。在磁场旋转的情况下，重复获得1.8%的循环场诱导应变。在恒定场向重复变化的情况下，只有在改变场向后的第一次试验中才会出现较大的场致应变。讨论了磁场对孪生位错的作用力及其产生的磁应力。对于较小的磁场，磁力与外加磁场成正比。在饱和场以上，磁应力是恒定的，等于磁各向异性常数与孪生剪切的比值。提出了一个将大场致应变与孪生位错运动联系起来的微观模型，并将其应用于实验。结果表明，只有改变磁场方向才能获得循环磁场感应应变，因为磁场力不能反转。将单晶Ni-Mn-Ga铁磁形状记忆试件在马氏体态下进行单轴压缩变形，总应变为2%。应力-应变曲线显示屈服点在6 Mpa处，然后是急流。在机械变形后，进行了恒强旋转磁场中的磁力试验和变强度恒向磁场中的磁力试验。在磁场旋转的情况下，重复获得1.8%的循环场诱导应变。在恒定场向重复变化的情况下，只有在改变场向后的第一次试验中才会出现较大的场致应变。讨论了磁场对孪生位错的作用力及其产生的磁应力。对于较小的磁场，磁力与外加磁场成正比。在饱和场以上，磁应力是恒定的，等于磁各向异性常数与孪生剪切的比值。一个微观模型。
A single-crystalline ferromagnetic Ni-Mn-Ga shape memory specimen was deformed in the martensitic state by uniaxial compression to a total strain of 2%. The stress-strain curve displays a yield point at 6 MPa followed by jerky flow. After mechanical deformation, magnetomechanical tests in a rotating magnetic field of constant strength as well as experiments in a magnetic field of variable strength and constant direction were performed. Upon field rotation, a cyclic-field-induced strain of 1.8% is obtained repeatedly. Upon repeated field variation with constant field direction, a large field-induced strain occurs only in the first test after a change of the field direction. The force of a magnetic field on a twinning dislocation and the resulting magnetostress are discussed. For small fields, the magnetic force is proportional to the applied field. Above the saturation field, the magnetic stress is constant and equals the ratio of the magnetic anisotropy constant and the twinning shear. A microscopic model relating large field-induced strain to the motion of twinning dislocations is presented and applied to the experiments. It is concluded that cyclic magnetic-field-induced strain can be obtained only by changing the field direction because the magnetic force cannot be reversed otherwise.A single-crystalline ferromagnetic Ni-Mn-Ga shape memory specimen was deformed in the martensitic state by uniaxial compression to a total strain of 2%. The stress-strain curve displays a yield point at 6 MPa followed by jerky flow. After mechanical deformation, magnetomechanical tests in a rotating magnetic field of constant strength as well as experiments in a magnetic field of variable strength and constant direction were performed. Upon field rotation, a cyclic-field-induced strain of 1.8% is obtained repeatedly. Upon repeated field variation with constant field direction, a large field-induced strain occurs only in the first test after a change of the field direction. The force of a magnetic field on a twinning dislocation and the resulting magnetostress are discussed. For small fields, the magnetic force is proportional to the applied field. Above the saturation field, the magnetic stress is constant and equals the ratio of the magnetic anisotropy constant and the twinning shear. A microscopic model...