Effects of temperature and pass number on mechanical properties, microstructure, and texture evolution in pure magnesium processed via a geometrically optimized TCAP method

• Geometrical Optimization of TCAP: • Through the optimized design of trapezoidal channel parameters, the process force was significantly reduced, enabling the successful processing of 1 mm thick magnesium tubes using the TCAP method for the first time. This achievement was accomplished without any tearing or punch buckling, marking a breakthrough in thin-walled tube manufacturing. • Effect of Process Temperature: • The TCAP process at 200°C, 250°C, and 300°C markedly improved ultimate tensile strength (UTS) and elongation (%) compared to the initial sample. • A maximum UTS increase of 32% was achieved at 250°C, while higher temperatures (350°C) led to decreased UTS and hardness. • Effect of TCAP Pass Number: • Increasing the number of TCAP passes at 200°C refined the grain size from 200 µm to 3 µm, improving hardness from 30 Vickers to 40 Vickers. • The second pass showed the highest improvements in UTS and elongation, reaching 1.26 and 1.3 times the initial values, respectively. The third pass, however, introduced microcracks, reducing strength and elongation • Texture Evolution: • At 200°C, a strong basal texture formed due to dominant basal slip. At 250°C, prismatic slip became more active, causing grain reorientation and a weaker basal texture. • At 350°C, static recrystallization (SRX) dominated, producing strain-free recrystallized grains and a more uniform texture distribution. • The first pass resulted in a split basal texture, weakened in the second pass due to dynamic recrystallization (DRX). The third pass enhanced basal texture intensity through selective recrystallization, stabilizing grain orientation. In this study, by optimizing the geometric parameters of the trapezoidal channel, the processing force in the Tubular Channel Angular Pressing (TCAP) process was reduced, and for the first time, 1 mm-thick magnesium tubes were processed using this method. At the beginning of the research, the process was simulated in ABAQUS software using a finite element model, and the effects of geometric parameters on processing force, equivalent strain, and strain inhomogeneity index were investigated. To study the effect of temperature and the number of passes on the improvement of mechanical properties, microstructure, and texture evolution, thin-walled magnesium tubes were processed at 200°C for three passes and at 250°C and 350°C for one pass. With an increasing number of passes, the grain size continuously decreased from the initial 200 µm to 3 µm, and the hardness increased from the initial 30 Vickers to 40 Vickers in the third pass. However, the greatest increase in strength and elongation occurred in the second pass, reaching 1.26 and 1.3 times the initial values, respectively. By increasing the temperature to 250°C, the ultimate tensile strength rose from the initial 73 MPa to 97 MPa, while increasing the temperature to 350°C resulted in a decrease in strength to 91 MPa. The observed mechanical properties were closely linked to texture evolution. At 200°C, a split basal texture formed due to dominant basal slip, while at 250°C, increased prismatic slip led to grain reorientation and weakening of the basal texture. At 350°C, static recrystallization (SRX) became the dominant mechanism, promoting grain growth and altering texture distribution. Additionally, dynamic recrystallization (DRX) initially weakened the basal texture, but subsequent recrystallization stabilized grain orientation, enhancing texture sharpening. Overall, the interplay between deformation mechanisms and recrystallization processes determined the final texture evolution, significantly influencing the mechanical properties of TCAP-processed tubes.