Relationship among grain size, texture and mechanical properties of aluminums with different particle distributions

Abstract

Relationship among grain size, texture and mechanical properties of aluminums with different particle distributions was investigated systematically by microstructure characterization, texture measurement and tensile test in the present study. The results reveal that there is a close relationship among grain size, texture and mechanical properties. For high-purity aluminum without particle, it is easy to result in the increase of grain size. As grain size increases, the initial texture Cube {001}<100> could become strong at first, and then transforms to other stronger texture components {011}<133> and {013}<293>. Furthermore, the strengths and elongation decrease due to the coarse grain structure, the plastic strain ratio r decreases and planar anisotropy Δr (absolute value) increases. For AlMgSiCu alloy with a large number of particles, it is difficult to make the grains grow. With increasing grain size, the texture consisting of Cube_ND {001}<310>, Goss {110}<001> and P {011}<122> orientations is slightly enhanced at first, and then transforms to another texture including Cube_RD {310}<001> and H {001}<110> orientations with a slight change in volume fraction. In addition, the strengths increase at first, and then remain constant, whereas elongation, r and Δr values are almost kept unchanged. In comparison with high-purity aluminum, AlMgSiCu alloy possesses the higher r and lower Δr values. In general, grain size plays an important role in texture development, not depending on whether the aluminum has particles, but particles could retard the texture transformation. Finally, variation of texture with grain size is explained by recrystallization progress.

Introduction

Metals often exhibit crystallographic texture, which is very important to their properties. It has been extensive applied in many fields [[1], [2], [3], [4]] that strong Goss texture {110}<001> is required to decrease the core loss of electrical steels, maximum Cube texture {001}<100> is expected to improve the capacity of high-purity aluminum foil, γ texture {111}<uvw> is beneficial to the deep drawability of automotive aluminum alloys, and a reasonable combination of texture components is preferable to decrease earing of aluminum alloy for packaging applications. In many cases, texture is induced intentionally or controlled by alloy element and processing optimizations to improve the specific properties, since it is greatly affected by some chemical elements, and processing parameters such as rolling parameters and heat treatment parameters [[5], [6], [7], [8]].

Recently, a series of studies [[9], [10], [11], [12]] have shown that texture could be significantly influenced by grain size. Large grain size always tends to strengthen texture. Strong Goss texture can be obtained in electrical steel by accelerating the growth of Goss-oriented grains [9,10]. Mao [11] pointed out that Cube texture could be dominant in high-purity face-centered cubic metals through the growth of Cube-oriented grains, which consume other oriented grains. The previous study [12] revealed that the coarse grain structure in AlMgSiCu alloy could result in the strong texture. However, the variation of texture with the grain size is not clear. In addition, both grain size and texture could influence the mechanical property, but there is no further relationship among grain size, texture and mechanical property in these studies.

It is well known that recrystallization texture is largely dependent on the fundamental recrystallization mechanisms [[13], [14], [15], [16], [17]]. In single-phase aluminum alloys, the recrystallization nucleation sites are always Cube bands, shear bands and grain boundaries, thus, Cube, Q {013}<231> and R {124}<211> orientations could be developed. In multi-phase aluminum alloys containing particles, recrystallization is further influenced by the precipitation state. Large particles with sizes larger than 1 μm can promote recrystallization by particle stimulated nucleation (PSN), thus, the weak Cube_ND {001}<310> and P {011}<122> texture components could be developed. Obviously, the particle distributions can also play a critical role in the development of texture besides grain size. Accordingly, it is difficult to understand whether the effect of grain size on texture could be influenced by particles. Until now, there is still lack of the related systematic work about the effect of grain size on the texture of the aluminums with different particle distributions, which is important for texture controlling. In order to investigate the relationship among grain size, texture and mechanical properties of aluminum alloys comprehensively, a high-purity aluminum without particle, and a AlMgSiCu alloy with a large number of particles were selected as the research object in the present study. The object of this investigation is to establish the relationship among grain size, texture and mechanical property. Hopefully, this work could provide a new insight for texture optimization.