Evolution in microstructure and properties during non-isothermal annealing of a cold-rolled Al–Mn–Fe–Si alloy with different microchemistry states

Abstract

The softening behaviour during non-isothermal annealing of a cold-rolled Al-Mn-Fe-Si model alloy was studied as a function of the state of microchemistry, in terms of the solute level of Mn, size and spatial distribution of the Mn-bearing dispersoids, as well as their temporal evolution. Microchemistry significantly affects the recrystallization microstructure, crystallographic texture as well as the mechanical property of the investigated alloy after non-isothermal annealing. The nucleation and growth of grains with different orientations are strongly dependent on both annealing temperature and microchemistry, in that pre-existing dispersoids have a less profound effect on retarding recrystallization than dispersoids forming concurrently during back-annealing. Strong concurrent precipitation suppresses nucleation and retards recrystallization, which finally leads to a coarse and pan-cake shaped grain structure, accompanied by strong P {011}<566> and/or M {113}<110> texture components and a relatively weaker ND-rotated cube {001}<310> component. A refined grain structure with medium strength P and cube {001}<100> components is obtained when the pre-existing dispersoids are coarser and fewer, and concurrent precipitation is limited. Porientated grains are less affected by second phase particles and experience a growth advantage at low annealing temperatures (<350°C), while M-orientated grains appear at higher temperatures. The intensity of the P texture does not necessarily increase with increasing supersaturation of Mn as observed during isothermal annealing, whereas the level of supersaturated Mn promotes the strength of the M texture. The mechanisms behind are discussed.

Effect of heterogeneously distributed pre-existing dispersoids on the recrystallization behavior of a cold-rolled Al–Mn–Fe–Si alloy

“…It is generally accepted that the presence of both the P-texture and ND-rotated cube is related to non-deformable constitutive particles and particle stimulated nucleation (PSN) of recrystallization, and it has been demonstrated experimentally by EBSD [8,13,14,17,18] and TEM [19,20] that P and ND-rotated cube oriented grains/sub-grains already are present within the deformation zone around constituent particles after deformation, from which they grow into the surrounding matrix. This fact has further been confirmed by numerical simulations of the texture evolution within the deformation zone of second-phase particles [21,22].…”

“…Nucleation at grain boundaries is thus largely suppressed, and only a few orientations (P-, M-oriented grains) can grow out of the deformation zone near the constituent particles, which finally leads to strong M or P texture components. The reason is their special boundary characteristics/orientation relationships with respect to the surrounding deformed matrix (with a typical rolling texture) making them less affected by concurrent precipitation [7,8], and moreover that they have an advantageous orientation relationship for growth [13]. The strength of the M texture component is stronger than that of the P texture component when recrystallization occurs at 350°C, see Fig.…”

“…As shown by their backscattered electron (BSE) micrographs, no significant precipitation occurred during these annealing experiments, however, if any, it should preferably be along grain/subgrain boundaries. However, for initial conditions of a super saturated solid solution, significant amounts of concurrent precipitation take place during low temperature annealing, preferentially at highangle grain boundaries and subsequently as well on low-angle grain boundaries before the onset of recrystallization [5,8,13], thus providing a condition of considerable amount of strongly heterogeneously distributed pre-existing dispersoids.…”

“…2b. A more comprehensive study on the recrystallization behavior of these conditions can be found in Refs [13,16].…”

“…The precipitation of dispersoids in the course of an annealing treatment can hinder or even totally suppress recrystallization [5,8,9]. Except the pancakeshaped coarse grain structures, specific texture components like P {011} b566N, M {113} b110N and ND-rotated cube {001} b310N are often observed when precipitation occurs concurrently with recrystallization [4][5][6]8,[10][11][12][13]. It is reported by Zeng et al [10] that the concurrent precipitation effect was not the sole reason responsible for the formation of the P texture component, fine pre-existing particles also give rise to the formation of the P orientation.…”