Microstructure gradient after hot torsion deformation of powder metallurgical 6061 Al alloy

Abstract

Abstract:The microstructure and the texture of extruded 6061 Al alloy processed by powder metallurgy (PM), using three different initial powder particle sizes, have been studied after torsion deformation at 300 • C at strain rate of 6 s −1 . The initial extruded microstructure of the three alloys consisted of elongated grains confining substructure with a typical 1 1 1 + 1 0 0 fiber texture. After torsion deformation, the torque ( ) as a function of the equivalent strain (ε eq ) showed softening and the microstructure exhibited a gradient across the section so that the inner and outer zones contained sheared-elongated and small-equiaxed subgrains, respectively. It was observed that the equivalent strain to failure for the material processed using powder particles size of less than 45 m was of about ε eq ∼ 12, compared to ε eq ∼ 1 for material processed using powder particles size of less than 25 m. The microstructural changes during hot torsion deformation of PM 6061 Al alloy should involve continuous dynamic processes.

Students’ project for instrumentation and automation of a manually operated torsion testing machine with educational purposes

“…16,15,14,17 The dynamical recovery and recrystallization during the rolling can be verified using torsion tests, which allow to replicate strain steps on a laboratory scale to assess the material susceptibility in cold processes or the dynamical recrystallization in hot processes. 16,15,18,17,19,20 In this context, this equipment has been used to develop Bachelor, Master, and Doctoral projects in the Undergraduate and Postgraduate Metallurgical Engineering programs of the Federal University of Ouro Preto.…”

“…Considering high plastic strain rates due to a predominantly shear stress field, the torsion test is important to develop models of constitutive phenomena of solid microstructures and to verify hardening characteristics of structures submitted to rotating efforts, which allows the reproduction of metallurgical effects for different strain levels and to replicate conditions similar to metallurgical processes of drawing and rolling on a laboratory scale. 16,15,14,17 The dynamical recovery and recrystallization during the rolling can be verified using torsion tests, which allow to replicate strain steps on a laboratory scale to assess the material susceptibility in cold processes or the dynamical recrystallization in hot processes. 16,15,18,17,19,20 In this context, this equipment has been used to develop Bachelor, Master, and Doctoral projects in the Undergraduate and Postgraduate Metallurgical Engineering programs of the Federal University of Ouro Preto.…”

A new preparation technology of structural-gradient materials without a brittle transition zone in a Mn-Si-Cr-B bainitic cast steel

“…Chemical composition of tested steel is listed in Table 1. The Ac 1 and Ac 3 temperatures were calculated to be 759 °C and 883 °C, respectively, according to the following equations [11] : (1) (2)…”

Texture and microstructural changes after thermal cycling of 6061Al-20vol%SiCw metal matrix composite: The role of microscopic internal stresses

“…In contrast, and despite the above studies on the thermal cycling creep behavior of MMCs, it is surprising that analyses from the point of view of the crystallographic texture changes are still scarce and incomplete [21,22]. Texture evolution has shown itself to be a powerful tool for investigating not only microstructural changes of materials undergoing different thermomechanical treatments, but also the underlying mechanisms responsible for them [23][24][25]. The texture/microstructure changes observed in the present work will be explained within the framework of the microscopic internal stress fields generated as a consequence of the large difference in the coefficient of the thermal expansion (CTE) between the matrix and the reinforcement (of about 6:1 in this composite).…”