Abstract
The texture evolution during hot compression of extruded ZK60A-T5 magnesium alloy plate loaded along the extrusion direction (ED) and the normal direction (ND) has been examined with the help of pole figures obtained on specimens deformed in the ranges of 200 °C to 500 °C and 0.0003 s−1 to 10 s−1. The results are interpreted in terms of the operating slip systems and mechanisms identified based on processing maps developed for the above two initial specimen orientations. The processing map for the initial ED orientation exhibited three domains. In Domains 1 and 3, first-order pyramidal slip {10 1 ¯ l} <11 2 ¯ 0> occurs, while in Domain 2, second-order pyramidal slip {11 2 ¯ 2} <11 2 ¯ 3> occurs. The pole figures obtained on specimens deformed in Domains 1 and 3 are strikingly similar, indicating that the operating slip system controls the texture evolution. Compression in Domains 1 and 3 nearly randomizes the intense basal texture in the as-received specimens, while a new texture is generated in Domain 2 with basal poles at 45° to ND or transverse direction (TD). This new texture will promote basal slip when loaded in a transverse direction. When loaded in the normal direction (ND), the processing map exhibited four domains. In Domains 1 and 4, {10 1 ¯ l} <11 2 ¯ 3> slip occurs, while {11 2 ¯ 2} <11 2 ¯ 3> slip occurs in Domains 2 and 3. The pole figures obtained from specimens deformed in Domains 1 and 4 have similar features, while those deformed in Domains 2 and 3 exhibited similar features to one another, confirming that the operating slip systems control the texture development since they are the same in each pair. The compression along ND produces strong basal textures with the basal planes normal to the ED. The texture gets intensified with increased temperature of deformation and causes strong anisotropy in mechanical properties.
Highlights
Given the availability of a limited number of slip systems in Mg at room temperature, thermomechanical processing is usually carried out at elevated temperatures to take advantage of the plasticity offered by the non-basal slip systems [1,2,3]
For deformation in normal direction (ND), less flow anisotropy is observed during the deformation at higher temperatures and lower strain rates, whereas more elliptical shapes evolved for the compression tests performed at higher strain rates of 10 and 1 s−1
The development of textures during hot compression of ZK60A-T5 magnesium alloy plate loaded along the extrusion direction (ED) and the direction normal to the extruded plane (ND) has been examined with the help of pole figures obtained on the deformed specimens
Summary
Given the availability of a limited number of slip systems in Mg at room temperature, thermomechanical processing is usually carried out at elevated temperatures to take advantage of the plasticity offered by the non-basal slip systems [1,2,3]. Hot deformation behavior of extruded (but not aged) ZK60 alloy was investigated by compression tests along the extrusion direction in the temperature range of 250–400 ◦ C and strain rate range of 0.001–1 s−1 [19], and its processing map revealed a domain of superplasticity and flow instability regions. The role of initial texture on the hot deformation behavior of extruded ZK60 alloy plate in T5 treated condition along extrusion direction and normal direction at a wide range of temperatures (200–500 ◦ C) and strain rates (0.0003–10 s−1 ) has not been documented. To serve as a ready reference for correlation, a brief summary of the results on processing maps published earlier [24] for ZK60 plate will be recalled first, which will be followed by the texture characterization of deformed specimens
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