Microstructure evolution, texture and laser surface HEACs of Al-Mg-Si alloy for light automobile parts

https://doi.org/10.1016/j.matchar.2019.110093Get rights and content

Highlights

  • Texture-strength of Cube{100}<001> increased with the Ce/Er addition.

  • F{111}<112> texture was varied, the strength of {110}//ND decreased.

  • Higher Cu content in Al-Mg-Si-Cu alloy led more β″ precipitates to be produced and refined.

  • Under hinders of UNs, the amorphous phases were not free to grow up.

Abstract

Effect of the rare earth (RE) elements and Cu on the microstructure performance and texture of the hot-rolled Al-Mg-Si alloys during the solution and artificial aging was investigated in this study. The results showed that Cube{100}〈001〉 and CubeND{001}〈310〉 textures were suppressed in a certain extent with the Ti/Zr addition, leading the Copper{112}〈111〉 and the {110}〈011〉 textures to be formed; the texture strength of Cube{100}<001> increased with Ce/Er-added, also the F{111}〈112〉 texture was varied, the strength of {110}//ND decreased. The orientation density of the hot-rolled T6 Al-Mg-Si-Cu alloys increased with the Ce/Er addition, the nucleation mechanism of the re-crystallization was the Cube texture, also the nucleation mechanism of the Cube texture and PSN were weaken. Then, the mixed powders of FeCoCrAlCu (high-entropy alloy powder)-MoSi2-Mn-Sb were deposited on the produced hot-rolled Ce/Er modified Al-Mg-Si-Cu alloy substrate by mean of a laser melting deposition (LMD) technique to form the high-entropy alloy composites (HEACs) to improve the surface performance of alloy substrate. Identification of the synthetic ultrafine nanocrystals (UNs) in LMD HEACs contributes theoretical/experimental basis to improve the quality of the laser 3D print materials. The research on the texture of the hot-rolled Al-Mg-Si-Cu alloy also the Co3Mo2Si UNs in laser-treated HEACs can provide the essential theoretical/experimental basis to improve the quality of the light alloys for the automobile parts.

Introduction

Heat-treatable Al-Mg-Si alloys are widely used as the body-sheet materials for the automobile parts due to their excellent performance, such as high strength, excellent formability and corrosion resistance [[1], [2], [3], [4], [5]]. Deformation strengthening is a very and practical also common method to improve the mechanical properties of the Al base light alloys. In the recent years, many studies have shown that addition of the appropriate amount of the RE elements led the microstructure to be refined, also texture controlling to be obtained, notably enhancing with the addition of RE, greatly restricting their commercial application in the automotive industries [[6], [7], [8]]. Consequently, lots of the researchers have also developed some Re-free or Re-low alloys' systems, such as the Al-Mg-Si or Al-Mo-Si alloy system, basing on the partial or complete substitution of RE by the other elements, offering an exceptional bond of the mechanical properties. Recently, large quantities of works have been done to apply the AM technology to fabricate the precision aircraft components, which could raise significantly the production efficiency, also save the production cost. Cu is often added to improve the microstructure performance of the Al-Mg-Si alloys, which can significantly increase the precipitation kinetics also the aging hardening response of this kind of alloys [[9], [10], [11]].

Pilot investigations [[12], [13], [14], [15]] indicated that Cu can promote the multi-phase to be produced in the composites during a laser-treated process; the prior studies [[16], [17], [18]] also showed that the texture is a key factor, which could greatly influence the mechanical properties of the alloys or composites. Recently, the preparations and properties of the HEACs on common substrate have attracted wide attention, which could greatly cut the cost of materials, also reveal the excellent performance [19]. Generally, the high-entropy alloys are made up of at least five principal elements, combined to a concentration of 5–35 at.% in to fabricate the high entropies of mixing (1.61R, compared to <0.69R for traditional alloys, where R is the gas constant) [[20], [21], [22]]. Recently, great number of work has been done in order to obtain the laser-treated HEACs with the characteristics of good oxidation/wear/corrosion resistance [23,24] or yield/tensile strength [25,26]. Nevertheless, less studies have been focus on the effects of the laser-induced technologies on the microstructure evolution of the nanocrystalline HEACs on the hot-rolled Al alloys in order to solve the surface wear problem of automobile materials. The concept of the laser-induced nanocrystalline HEACs is proposed, i.e. using the special chemical elements to fabricate the UNs reinforced HEACs on alloys by mean of a LMD technique. Through the experimental work, large quantities of UNs were produced after a LMD process. In this study, the influence of Cu on the microstructure performance and texture of the hot-rolled Al-Mg-Si alloys, also the combined Cube texture/PSN and nucleation mechanisms are discussed in detail. To have a quantitative understanding of the LMD technology and the laser strengthening effects, this paper has provided the laser technology and the related theoretical basis to fabricate the laser induced UNs modified composites on Al alloys. This study provided basic theoretical/experimental information to upgrade the quality of the light alloys for automobile.

Section snippets

Experimental section

The asymmetrical rolling technique can greatly decrease the pressure of rolling, raise the machining efficiency of the hot-rolled sheets, these produced sheets exhibit the good microstructure performance; also the asymmetrical rolling has a deformation behavior, which is able to further improve the microstructure performance of rolled sheets. Thus, the Al-Mg-Si-Cu alloys thin sheets that fabricated by mean of an asymmetrical rolling technique were used. During the Al-Mg-Si-Cu alloys'

Microstructures and crystals' growth

The room temperature tensile test was carried out by a DNS200 universal material tensile testing machine, the drawing speed was 2 mm/min; micro-hardness distribution of the hot-rolled Al-Mg-Si-Cu alloys was measured by MH-5L microsclerometer; microstructure morphologies of these alloys were analyzed by means of a Leica-DMI 3000M microscope, an EBSD, a pole figure (PF), inverse pole figure (IPF) and orientation distribution function (ODF). The microstructures of the hot-rolled Al-Mg-Si-Cu alloys

Conclusions

In summary, the hot-rolled Al-Mg-Si-Cu alloys exhibited the fibrous microstructures under an action of the roll force when degree of the rolling deformation was high enough, also lots of the residual phases were existed. The static recovery/recrystallization occurred in the hot-rolled Al-Mg-Si-Cu alloys sheets during T6, also the hot-rolled fibrous microstructure was disappeared, resulting in the recovery/recrystallization microstructures. In the hot-rolled Al-Mg-Si-Cu alloys sheets after T6,

Declaration of competing interest

The authors declared that they have no conflicts of interest to this work. We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted. The paper has not been published previously, that it is not under consideration for publication elsewhere, and that if accepted it will not be published elsewhere in the same form, in English or in any other language, without the written consent of the publisher

Acknowledgements

This work was financially supported by project ZR2019YQ25 supported by Shandong Provincial Natural Science Foundation, the Taishan Scholars Program of Shandong Province National Natural Science Foundation of China (Grant No. 51505257).

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