Abstract: Due to their high strength, high toughness, and corrosion resistance, high-strength aluminum alloys have attracted great scientific and technological attention in the fields of aerospace, navigation, high-speed railways, and automobiles. However, the fracture toughness and impact Toughness of high-strength aluminum alloys decrease when their strength increases.
In order to solve the above contradiction, there are currently three main control strategies: adjusting the alloying elements, developing new heat treatment processes, and using different deformation methods. This paper first analyses the existing problems in the preparation of high-strength aluminum alloys, summarizes the strengthening and toughening mechanisms in high-strength aluminum alloys, and analyses the feasibility of matching high-strength aluminum alloys in strength and toughness.
Then, this paper summarizes the research progress towards adjusting the technology of high-strength aluminum alloys based on theoretical analysis and experimental verification, including the adjustment of process parameters and the resulting mechanical properties, as well as new ideas for research on high-strength aluminum alloys. Finally, the main unsolved problems, challenges, and future research directions for the strengthening and toughening of high-strength aluminum alloys are systematically emphasized.
It is expected that this work could provide feasible new ideas for the development of high-strength and high-toughness aluminum alloys with high reliability and long service life.
New Ideas for Strengthening and Toughening High-Strength Aluminum Alloys
(1) Interest in the study of the strength and toughness of HSAA continues to grow at Home and abroad. To explore new ideas for the strengthening and toughening of HSAA, The latest strengthening and toughening strategy of alloy can be discussed.
(2) Pre-Aged Hardening Warm Forming (PHF) Process L. Hua proposed a new forming technique, called the pre-aged hardening warm Forming (PHF) process, for heat-treatable aluminum alloys. Figure 2 shows the PHF Process route and rationale. In this technology, the used alloy is heat-treated and pre-aged as a billet, and then the pre-aged billet is heated to a lower temperature and soaked for a Short time, subsequently transferring the load to be heat treated.
(3) The pre-aged Blanks are provided by sheet metal suppliers, and these pressing procedures can be finished in minutes, resulting in short production cycles and low costs. The results suggested that the elongation of the pre-aged alloy was 5% to 16% greater than that of the O-temper of 200 _C. The tensile strength results showed that the stamping parts reached S/s 0.2 = 566 MPa, which exceeds the strength of the 7075 alloy. The influences of phase Transformation and plastic deformation during the PHF process improved the impact Resistance of these parts.
Conclusions and Prospects
At present, HSAA are developing towards higher strength, higher toughness, corrosion Resistance, and higher specifications. Research on improving the strength and Toughness of HSAA mainly focuses on adjusting the alloy composition (such as by adding New alloy elements) and developing new processing and manufacturing technologies.
Although HSAA are used in various frontier fields, and researchers have achieved many Promising results, efforts still need to be made in the following aspects:
(1) In the HSAA matrix, there are grain boundary precipitates, micron-scale crystallization Precipitates, sub-micron high-temperature precipitates, and even Nano-scale Intragranular aging precipitates. The mechanisms by which the morphology, size, Quantity, and distribution of these phases influence the mechanical properties and Corrosion resistance of HSAA need to be further studied.
(2) In terms of alloying elements, the influences of the ratio of Zn, Mg, and Cu, the Contents of trace elements, and the contents of rare earth elements on the optimization Of comprehensive mechanical properties of HSAA are still controversial. The coordination Of element content is an urgent problem to be relieved. Further reductions In the content of Fe, Si and other impurities, improvement in the purity of alloys, And improvements in the strength, fracture toughness, fatigue resistance and stress Corrosion cracking resistance of high-strength aluminum alloys are needed. When the Contents of Fe and Si are less than 0.1%, the above properties will be greatly improved.
(3) Heat treatment optimizes the mechanical properties by adjusting the size and number Of grains, along with the mechanism by which the size and distribution of the second Phase particles at the grain boundaries influence the corrosion resistance, which Are issues worthy of study? First, it is necessary to continue to optimize the aging Treatment process to obtain the best combination of strength, toughness and corrosion Resistance of alloys; second, optimized two-stage or multi-stage aging is still in the Primary application stage, and the application of existing achievements should be Accelerated.
(4) New deformation methods can significantly refine grains, inhibit segregation, make Precipitates evenly distributed and improve the super saturation of various elements. Therefore, the research and development of new deformation methods is also crucial For future breakthroughs. It is necessary to adopt and study various advanced and Special processing methods, such as superplastic forming, precision die forging, Isothermal die forging, semi-solidification die forging, isothermal extrusion, and thick Plate forging and rolling, to improve the comprehensive and special properties of Alloys.
Reference link https://pubmed.ncbi.nlm.nih.gov/35806849/
