Effect of pre-deformation thermomechanical processing on the development of ultrafine grain structure during equal channel angular extrusion

Abstract Two different microstructures, i.e., fine-grained solute depleted (FGSD) and coarse-grained solute enriched (CGSE), are prepared by thermomechanical processing. The samples are subjected to six pass equal channel angular pressing (ECAP). EBSD indicates formation of an ultrafine grained (UFG) structure within a size range of 632 nm in FGSD in comparison to 727 nm in CGSE which is attributed to more significant grain fragmentation in the FGSD sample with higher surface area of boundaries. In both as-annealed and -deformed conditions, hardness, yield strength (YS) and ultimate tensile strength (UTS) of the CGSE samples are higher than those of FGSD which is attributed to more significant solute enrichment. Elongation is found to reduce by the initial passes of ECAP and gradually improve by further processing. At a similar deformation history, the uniform elongation of the deformed CGSE samples is higher than those of the deformed FGSD samples which is attributed to more significant solute enrichment and work hardening causing a delayed necking and larger uniform elongation. However, the elongation to failure of FGSD samples after 2, 4 or 6 pass ECAP is larger than the CGSE sample with a similar deformation history which may be due to the high capacity of boundaries to accommodate dislocations and postpone fracture.

[1]  R. Kaibyshev,et al.  Effect of second phase particles on grain refinement during equal-channel angular pressing of an Al–Mg–Mn alloy , 2012 .

[2]  Patrick B. Berbon,et al.  OBSERVATIONS OF HIGH STRAIN RATE SUPERPLASTICITY IN COMMERCIAL ALUMINUM ALLOYS WITH ULTRAFINE GRAIN SIZES , 1997 .

[3]  N. Gao,et al.  PREDICTING GRAIN REFINEMENT BY COLD SEVERE PLASTIC DEFORMATION IN ALLOYS USING VOLUME AVERAGED DISLOCATION GENERATION , 2009 .

[4]  S. Ringer,et al.  Microstructural evolution of Fe-rich particles in an Al-Zn-Mg-Cu Alloy during equal-channel angular pressing , 2010 .

[5]  J. P. Fuertes,et al.  Design and mechanical property analysis of AA1050 turbine blades manufactured by equal channel angular extrusion and isothermal forging , 2013 .

[6]  E. El-Danaf.  Mechanical properties, microstructure and texture of single pass equal channel angular pressed 1050, 5083, 6082 and 7010 aluminum alloys with different dies , 2011 .

[7]  Y. Estrin,et al.  Extreme grain refinement by severe plastic deformation: A wealth of challenging science , 2013 .

[8]  F. J. Humphreys,et al.  Recrystallization and Related Annealing Phenomena , 1995 .

[9]  R. Valiev,et al.  Principles of equal-channel angular pressing as a processing tool for grain refinement , 2006 .

[10]  Ruslan Z. Valiev,et al.  Deformation behavior of nanostructured aluminum alloy processed by severe plastic deformation , 2001 .

[11]  A. Taheri,et al.  A new method for estimating strain in equal channel angular extrusion , 2007 .

[12]  A. Taheri,et al.  Modeling age hardening kinetics of an Al-Mg-Si-Cu aluminum alloy , 2008 .

[13]  M. Fu,et al.  Fabrication of bulk ultrafine grained titanium alloy via equal channel angular pressing based thermomechanical treatment , 2013 .

[14]  U. Mallik,et al.  Evaluation of grain refinement and variation in mechanical properties of equal-channel angular pressed 2014 aluminum alloy , 2009 .

[15]  A. Zarei‐Hanzaki,et al.  The second phase particles and mechanical properties of 2124 aluminum alloy processed by accumulative back extrusion , 2014 .

[16]  Y. Birol.  Precipitation during homogenization cooling in AlMgSi alloys , 2013 .

[17]  M. I. A. E. Aal,et al.  Influence of the pre-homogenization treatment on the microstructure evolution and the mechanical properties of Al-Cu alloys processed by ECAP , 2011 .

[18]  Seyed Masoud Ashrafizadeh,et al.  Correlative evolution of microstructure, particle dissolution, hardness and strength of ultrafine grained AA6063 alloy during annealing , 2015 .

[19]  R. Valiev,et al.  Bulk nanostructured materials from severe plastic deformation , 2000 .

[20]  K. T. Ramesh,et al.  Deformation behavior and plastic instabilities of ultrafine-grained titanium , 2001 .

[21]  R. Valiev,et al.  Achieving Exceptional Grain Refinement through Severe Plastic Deformation: New Approaches for Improving the Processing Technology , 2011 .

[22]  R. Lapovok,et al.  The role of back-pressure in equal channel angular extrusion , 2005 .

[23]  H. Vehoff,et al.  Plastic deformation mechanism of ultra-fine-grained AA6063 processed by equal-channel angular pressing , 2010 .

[24]  B. Mirzakhani,et al.  Combination of sever plastic deformation and precipitation hardening processes affecting the mechanical properties in Al–Mg–Si alloy , 2015 .

[25]  V. Segal.  Materials processing by simple shear , 1995 .

[26]  Mohsen A. Hassan,et al.  The application of equal channel angular pressing to join dissimilar metals, aluminium alloy and steel, using an Ag-Cu-Sn interlayer , 2015 .

[27]  Joong-Keun Park,et al.  Microstructure and mechanical properties of Al-7075 alloy processed by equal channel angular pressing combined with aging treatment , 2014 .

[28]  P. Venugopal,et al.  Analysis of forming loads, microstructure development and mechanical property evolution during equal channel angular extrusion of a commercial grade aluminum alloy , 2003 .