PSI - Issue 21

Nathaniel Mupe et al. / Procedia Structural Integrity 21 (2019) 73–82 Mupe et al./ Structural Integrity Procedia 00 (2019) 000 – 000

81

9

1 pass but varied at 473 K and 523 K. The increase in yield strength at 473 K was as a result of strong texture whose c-axis of the HCP structure settled almost perpendicular to the tensile direction. The decrease of YS and UTS at 523 K was attributed to the alignment of the HCP cells on the basal plane in a manner that triggered slip. The slight improvement in elongation with grain size reduction was also observed by [Xia et al. (2014)]. Table 2 shows a summary of results of equivalent strains, grain size, processing temperatures, hardness, tensile strength and yield strength from various SPD methods on AZ31 alloy. It is evident that NTE was more superiors in grain refinement of extruded AZ31alloy than ECAP and HPT techniques indicated. 5. Conclusions Nonlinear twist extrusion has been conducted on wrought AZ31 alloy as extruded up to 1 pass at temperatures of 373 K, 473 K and 523 K. The following main observations are made from this study:  AZ31 was successfully deformed through NTE for 1 pass at temperatures as low as 373 K without the formation of cracks on specimen surface. Back pressure was not applied. This low temperature deformation is accomplished by uniform deformation of NTE with less strain localization and rigid body rotation which is seen in the conventional TE.  Grain refinement improved as the temperatures increased to 373 K, 473 K and 523 K. NTE was more effective in refining grains compared to the other SPD processes with significant high result of 3.1 µm attained at 523 K. This could be a result of less strain reversal, but more detailed examination is required in the future.  The higher hardness is a result of grain refinement, twinning and strain hardening which occur at lower deformation temperature. The hardness was significantly increased to 104 Hv at 473 K.  NTE was confirmed to be a promising technique for processing AZ31 alloys resulting to significant improvement of materials mechanical properties. References Agnew, S., Horton, J., Lillo, T., & Brown, D. (2004). Enhanced ductility in strongly textured magnesium produced by equal channel angular processing. Scripta Materialia, 50, 377 – 381. Beygelzimer, Y., Orlov, D., & Varyukhin, V. (2002). A new severe plastic deformation method: Twist extrusion. Proceeding of the Second International Symposium on Ultrafine Grained Materials II, TMS, (pp. 297-304). Seattle, Washington, USA. Bryla, K., Dutkiewicz, J., Litynska-Dobrzynska, L., Rokhlin, L., & Kurtyka, P. (2012). Influence of number of ECAP passes on microstructure and mechanical properties of AZ31 magnesium alloy. Archives of Metallurgy and Materials, 57(3), 711-717. Chengpeng, W., Fuguo, L., Bo, C., Zhanwei, Y., &Hongya, L. (2012). Severe Plastic Deformation Techniques for Bulk Ultrafine-grained Materials. Rare metal materials and engineering, 41(6), 941-946. Fatemi-Varzaneh, S., Zarei-Hanzaki, A., Cabrera, J., & Calvillo, P. (2015). EBSD characterization of repetitive grain refinement in AZ31 magnesium alloy. Materials Chemistry and Physics 149-150, 339-343. Galiyev, A., Kaibyshev, R., & Gottstein, G. (2001). Correlation of plastic deformation and dynamic recrystallization in Magnesium alloy ZK60. Acta mater, 49, 1199 – 1207. Gzyl, M., Rosochowski, A., Boczkal, S., & Olejnik, L. (2015). The role of microstructure and texture in controlling mechanical properties of AZ31B magnesium alloy processed by I-ECAP. Materials Science & Engineering A, 638, 20 – 29. Gzyl, M., Rosochowski, A., Pesci, R., Olejnik, L., Yakushina, E., & Wood, P. (2013). Mechanical Properties and Microstructure of AZ31B Magnesium Alloy Processed by I-ECAP. Metallurgical and Materials Transactions A, Springer Verlag/ASM International, 45(3), 1609-1620. Han, T., Huang, G., Wang, Y., Wang, G., Zhao, Y., & Pan, F. (2016). Enhanced mechanical properties of AZ31 magnesium alloy sheets by continuous bending process after V-bending. Progress in Natural Science Materials International, 26(1), 97-102. Hilšer, O., Rusz, S., Maziarz, W., Dutkiewicz, J., Tański, T., Snopiński, P., & Džugan, J. (2017). Structure and Properties o f AZ31 Magnesium Alloy after Combination of Hot Extrusion and ECAP. Acta Metallurgica Slovaca, 23(3), 222-228. Huang, Y., Figueiredo, R. B., Baudin, T., Helbert, A.-L., Brisset, F., & Langdona, T. G. (2013). Microstructure and Texture Evolution in a Magnesium Alloy During Processing by High-Pressure Torsion. Materials Research, 16(3), 577-585. Kim, W. J., & Jeong, H. T. (2005). Grain-Size Strengthening in Equal-Channel-Angular-Pressing Processed AZ31 Mg Alloys with a Constant Texture. Materials Transactions, 46(2), 251-258.