【正文】 ination of high strength and ductility could be achieved in precipitation hardening alloys through severe plastic deformation followed by annealing/ ageing treatments. In the present work, the solutionised plates of an AlMgSi alloy (modified AA6061 alloy)were subjected to severe cold rolling at room and liquid nitrogen temperatures to a true strain ? . The rolled sheets were aged to induce precipitation. The equilibrium second phase distribution for the above alloy was calculated using CALPHAD. The rolled and aged samples were analysed using differential scanning calorimetry (DSC), Xray diffraction (XRD), transmission electron microscopy (TEM), hardness and tensile tests. The stored energy obtained from DSC measurements was found to be independent of the rolling temperature. The volume fraction of S {123} ＜634＞ orientation is predominant (? 40%) in both the rolling conditions. The strength and ductility were simultaneously improved following ageing of the cryorolled (CR) and room temperature rolled (RT) samples. Transmission electron microscopy analysis revealed dislocation cell structures in the CR and RT conditions. Analysis of second phases revealed fine spherical Mn rich precipitates (most likely Al6Mn) following ageing. 1 IntroductionAluminum alloys are widely used for fabricating high strength and light weight structures in automotive and aerospace applications. 6XXX alloys (AlMgSi based) have been studied extensively because of their high strength, good formability, weldability and corrosion resistance. In the last decade, severe plastic deformation (SPD) techniques such as equal channel angular pressing (ECAP), accumulative roll bonding (ARB), multiple pression and high pressure torsion (HPT) have been extensively researched to achieve grain refinement in polycrystalline materials . The SPD processes however, require large amount of plastic deformation and special experimental procedures. Recently, deformation (rolling) at cryogenic (liquid nitrogen) temperature and low temperature annealing has also been shown to produce ultrafine grained (ufg) microstructures in Cu, Al, AA5083, AA2219 and Ni . Suppression of dynamic recovery during cryogenic deformation results in high defect density, which in turn leads to increased nucleation sites during annealing resulting in a finer grain structure . However, achieving a reasonable ductility in these materials is still a challenge. Recent results have shown that the bination of high strength and ductility could be achieved in precipitation hardening alloys through severe plastic deformation followed by annealing/ageing treatments. The precipitation sequence during ageing of Al alloys is plex and goes through many intermediate stages before the formation of equilibrium precipitates. In AlMgSi alloys, the sequence of precipitation from the supersaturated solid solution is generally believed to be zones→β″→β′→β(Mg2Si, equilibrium). For a given ageing temperature, the sequence and type of phases that form are strongly position dependent. These in turn are determined by the equilibrium phases that may eventually form in these alloys. Evolution of equilibrium phases for any given position and temperature can be calculated using the CALPHAD procedure . It is well known that crystallographic texture controls the formability of the Al alloys. Crystallographic texture develops in metals and alloys when subjected to large deformation and/or annealing. Rolling/deformation textures in Al alloys are characterized by the β fiber running from copper orientation {112} ＜111＞over the S orientation {123} ＜634＞ to the brass orientation {011} ＜211＞. The recrystallization texture ponent is dominated by strong cube orientation {001}＜100＞ and Goss orientation {110} ＜001＞[21].In this work, a modified version of age hardening AA6061 alloy (designated as 6061M) was subjected to rolling at liquid nitrogen 09215093/ temperature (77K) (here after referred to as CR) and at room temperature (here after referred to as RT). We present the microstructure, texture and mechanical properties of the alloy 6061M in the rolled (CR and RT) and in the rolled and aged conditions. The differences between the conventional AA6061 and 6061Mare explained on the basis of phase fraction calculations for the alloys using CALPHAD procedure.2. Experimental procedureThe 6061M alloy was procured in the form of plates of thickness. These plates were solutionised at 535 ℃ for 1 h and quenched in water and subsequently rolled (at room temperature and at liquid nitrogen temperature) from to in multiple passes with about 10% reduction per pass. For rolling at liquid nitrogen temperature, the solutionised plates were dipped in liquid nitrogen for 15min and after each pass the plate was immersed in liquid nitrogen for 2 min before further reduction. Differential scanning calorimetry (DSC) was used to identify the recovery and recrystallization temperatures of the alloy. To study the age hardening behaviour, the CR and RT rolled samples were subjected to ageing at 100, 125 and 150 ?C for varying times (1–36 h) in a tubular furnace. Vickers hardness was measured using 100 g load on rolled and aged samples. Xray diffraction was done on CR, RT rolled and annealed samples using the CuK radiation. Pure Al powder annealed at 300 C in Ar atmosphere was used as reference in XRD peak broadening for microstrain calculation. Uniaxial tensile tests were conducted at an initial strain rate of 310?3 s?1 on specimens that were machined as per ASTM E8 subsize specifications. For Xray texture analysis {200}, {111}, {110} and {113} pole figures were measured (on the surface of samples) on a Phillips Xray texture goniometer using CuK radiation. From inplete pole figure data, orientation distribution function (ODF) and quantitative texture ponents are calculated using LABOTEX software . Microstructural characterization was carried out using Philips CM12 transmission electron microscope (TEM) op