Superior Strength and Ductility of In Situ Nano TiB2/Al–Cu–Mg Composites by Cold Rolling and Post-Aging Treatment

Junhui Tang,Jiwei Geng,Cunjuan Xia,Dong Chen,Haowei Wang,Mingliang Wang

doi:10.3390/ma12213626

Abstract

In this work, the combination of cold rolling with post-aging treatment is developed to achieve the optimal strength–ductility for the in situ nano TiB2/Al–Cu–Mg composite. The microstructure and mechanical properties of the composite subjected to 20% thickness reduction of cold rolling at room temperature and their evolutions upon post-aging at different temperatures were investigated by means of a tensile test, differential scanning calorimetry, scanning electron microscopy, and transmission electron microscopy. It was found that the TiB2 particles were effective in dislocation pinning and accumulation during the cold-rolling process. The tensile tests indicated that both the yield and ultimate tensile strengths of the cold-rolling sample increased a lot due to the dislocation strengthening and precipitation strengthening generated by dynamic precipitation during cold rolling in comparison with the conventional T6 sample. After aging at 100 °C/12 h, the elongation to failure reached ~8.4%, which was higher than the conventional T6 sample. Meanwhile, there was also a dramatic increase of strength. The yield and ultimate tensile strengths are ~644 MPa and ~726 MPa, respectively. This remarkable strength–ductility combination was due to the modified microstructure caused prior to artificial aging by the cold-rolling method and the formation of nanosized Guinier–Preston–Bagaryatsky (GPB) zones. The underlying mechanisms related to the superior strength–ductility combination were discussed regarding the microstructural characteristics in the composite.

Highlights

Strength and ductility are two of the most important mechanical properties for structural materials.they are often in conflict with each other
The more difficult it is for dislocations to appear and to move, the stronger but more brittle and less ductile any crystalline material is [1]
The in situ 6 wt.% TiB2/2024 composite with a major composition of Al–4.63Cu–1.77Mg–0.71Mn in matrix alloy was fabricated by the addition of a pre-weighted mixture of K2 TiF6 and KBF4 in matrix alloy was fabricated by the addition of a pre-weighted mixture of K2TiF6 and KBF4 salts into the 2024 alloy melt at 850 ◦ C through an exothermic reaction

Summary

Introduction

Strength and ductility are two of the most important mechanical properties for structural materials. They are often in conflict with each other. The more difficult it is for dislocations to appear and to move, the stronger but more brittle and less ductile any crystalline material is [1]. There is a strong push to improve the strength–ductility combination of Al-based materials for aerospace and automobile applications. The Al–Cu–Mg alloy is one of the most commonly used aerospace Al alloys due to their attractive mechanical properties [2,3,4]. A number of methods have been developed to improve its strengths.

Methods

Results

Conclusion