Study On Martensitic Transformation And Mechanical Properties And Magnetic Properties Of Ni-Mn-Sn-Gd Alloy

Ni50Mn36Sn14-x Gdx(x = 0, 0.1, 0.2, 0.5, 1, 2 at %) magnetic shape memory alloy were prepared by vacuum arc melting method. The microstructures,martensitic transformations, mechanical, magnetic properties, and their influences on Ni-Mn-Sn magnetic shape memory alloys have been investigated by means of SEM, XRD, compressive tests and so on.The experimental results show that the crystal grains of Ni-Mn-Sn alloys can be apparently refined by increasing Gd content,and with the increase of Gd content,the grain size decreases. Ni-Mn-Sn-Gd alloys consists of the Ni-Mn-Sn matrix and the second phase. With the increase of Gd content, the second-phase grows and its volume fraction increases gradually, and mainly along the grain boundaries.The magnetic measurement illustrates that Ni-Mn-Sn-Gd alloys undergo one-step thermoelastic martensitic transformation during the process of cooling and heating. Martensitic transformation temperatures of Ni-Mn-Sn-Gd alloys increase with the increase of Gd content, which is mainly due to the presence of the Gd(Ni,Mn)4Sn precipitate, resulting in the increase of Mn content in the matrix. Gd addition improves the mechanical properties of Ni-Mn-Sn-Gd alloys without damage of the magnetic properties.Compression tests show that an appropriate amount of Gd addition has significantly improved the mechanical properties of Ni-Mn-Sn alloy. Both the compressive strength and strain have a strong dependence upon the Gd content.When the Gd content is 1at.%. With the increase of Gd content, the hardness of matrix increased gradually, and the hardness of second-phase is higher than the matrix. The compressive strength and strain reach the maximum value. Thefracture type of Ni-Mn-Sn alloy changes from intergranular fracture of Ni-Mn-Sn alloy to transgranular cleavage fracture with increasing Gd content.