Introducing equiaxed grains and texture into Ni-Mn-Ga alloys by hot extrusion for superplasticity. (15th December 2016)

• Record Type: Journal Article
• Authors: Wei, Longsha; Zhang, Xuexi; Qian, Mingfang; Cui, Xiping; Geng, Lin; Sun, Jianfei; Panina, Larissa V.; Peng, Hua-Xin
• Is Part Of: Materials & design. Volume 112(2016)
• Page Start: 339
• Page End: 344
• Publication Date: 2016-12-15
• Subjects: Superplasticity -- Hot extrusion -- Texture -- Dynamic recrystallization -- Ni-Mn-Ga; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2016.09.076
• Languages: English
• ISSNs: 0264-1275

Abstract

Abstract: Ni-Mn-Ga alloys are generally brittle, making it difficult for shaping complex components by conventional plastic deformation. Here we demonstrated that superplastic deformation capability occurred in a Ni47.4 Mn31.5 Ga21.1 alloy prepared by extrusion. The extrusions were carried out at 1273 K and 1323 K with extrusion ratios of 9:1, 12:1 and 16:1, in which equiaxed grains and a 〈111〉 texture were created by the coupled dislocation slip and dynamic recrystallization process. The size of the equiaxed grains, varied from 61.8–75.7 μm, showed a stronger dependence on extrusion temperature than the extrusion ratio. At a strain rate of 10 − 3 s − 1 and temperature of 1073 K, the extruded alloy exhibited a tensile superplastic elongation of 225.0%, much higher than that in the as-cast alloy (57.9%). This shows that the B2 phase exhibits a good superplastic deformation capacity at temperature above the ordering temperature. The mechanism of the superplasticity in the extruded alloys was determined to be the dynamic recrystallization process driven by the accumulated dislocations formed through dislocation slip. Graphical abstract: Highlights: Ni47.4 Mn31.5 Ga21.1 alloy was extruded at temperatures 1273 and 1323 K with maximum extrusion ratio of 16:1. Equiaxed grains with diameters 61.8-75.7 μm and <111> texture were created in the extruded Ni47.4 Mn31.5 Ga21.1 rods. The superplasticity of the extruded alloys with maximum elongation 225 % was demonstrated at 1073 K and 10 – 3 s – 1 . The superplastic deformation mechanism of Ni-Mn-Ga alloys was determined to be dislocation slip and dynamic recrystallization.