Search

Over the past few years, researchers have developed the alloy Al-Mg-Zn(-Cu), a new aluminum alloy based on the technique of ‘crossover alloying’. The main strengthening phase of this novel alloy is T-Mg32(Al, X)49(X is Zn and Cu) after ageing and hardening. This alloy system has exceptional strength and corrosion resistance, making it a promising candidate for applications in fields like automotive, marine, aerospace, and many others. In this work, the research progress of the Al-Mg-Zn(-Cu) alloy based on microstructure control, composition, design, and properties has been reviewed. Future directions for the research of this alloy are highlighted, too. In this work, crossover alloys are presented as a potential novel class of Al alloys implicating a pioneering design approach, with particular emphasis on the aeronautical and aerospace field in which radiation resistance results are one hundred times higher than traditional precipitation hardening alloys.

Modern industrial development has put forward higher demands on the performance of metallic structural materials, especially in terms of light weight, high strength and corrosion resistance. All of these characteristics are of particular importance in transportation fields. As one of the most representative structural materials, aluminum and alloys have exhibited significant advantages in light weight. Most of the alloys are prominently featured in one specific aspect. The overall performance still needs to be improved. In recent years, researchers have developed Al-Mg-Zn(-Cu) alloy, a new wrought aluminum alloy, whose design strategy is known as “crossover alloying”. This novel alloy is an age-hardened Al-Mg alloy with a T-Mg32(Al, X)49 (X is Zn, Cu) phase as the main strengthening phase. This system of alloys exhibits excellent properties in terms of strength and corrosion resistance, which makes it promising for applications in automotive, marine, aerospace and other fields. This paper summarizes the research progress of Al-Mg-Zn(-Cu) alloy, and analyzes the basic methods of microstructural control in terms of composition design and property research. Finally, the future directions of this alloy are proposed.

A growing demand for resources has led to the expansion of agricultural areas worldwide. However, land conversion associated with poor soil management might lead to soil physical degradation. We investigated the effects of land conversion on soil physical properties in the Brazilian Cerrado region, under native Cerrado vegetation (NV)—pasture (PA) and NV—cropland (CL) conversion scenarios. Soil physical properties related to compaction, pore size distribution, and structure stability were assessed up to a 30 cm depth. Additionally, carbon levels of soil organic matter fractions (particulate and mineral-associated organic matter) were determined. Our results indicate that the compaction process equivalently reduced the soil porosity in PA and CL. However, soil penetration resistance was higher in PA (~2.5 MPa) than in CL (~1.5 MPa), as well as the stable mean weight diameter of soil aggregates. The highest total and labile organic carbon levels were observed in CL, while the lowest levels of total and labile organic carbon occurred in PA (smaller than in CL). These results suggest that the higher structural stability found in PA was mediated by the predominance of stabilized carbon (a decrease in the proportion of soil labile carbon), causing the gaining of soil strength under negligible soil volume variation (in comparison with CL). Our results suggest that the reduction in the soil porosity by compaction due to PA and CL uses can equivalently reduce macropore space and soil hydraulic functioning, and that soil carbon quality alterations (i.e., labile vs. stabilized fractions) are responsible for the gain in soil strength in long-term degraded PA areas. Future research should focus on understanding the magnitude in which soil organic matter controls soil physical attributes, such as soil strength in these expansion areas, and whether this gain in soil strength limits plant development and compromises productivity in the long term.

Two types of nanoclusters, Cluster (1) and Cluster (2), formed at around room temperature and 100 °C, respectively, affect the age-hardening behavior in Al-Mg-Si alloys. Formation of Cluster (1) during natural aging (NA) is more accelerated in the high-Mg (9M10S) alloy than in the low-Mg (3M10S) alloy. Hardness at the early stage of two-step aging at 170 °C is not increased for the natural aging samples. On the other hand, hardness is directly increased for the pre-aged (PA) specimens. Furthermore, the formation of Cluster (1) during natural aging is suppressed by the formation of Cluster (2) during pre-aging at 100 °C. To understand the effects of heat treatment histories and Mg contents on the microstructure, transmission electron microscopy (TEM) was utilized. All the images were obtained at (001) plane, and peak aged samples with different heat treatments were used. Lower number density of precipitates is confirmed for the natural aging samples compared with the single-aged and pre-aged specimens. A higher number density of precipitates is confirmed for 9M10S in comparison to 3M10S. Hardness results correspond well to the TEM images.

The age-hardening behaviour and microstructure development of high strength Ni-based superalloys ABD-D2, D4, and D6 with varying Nb/Ti ratios have been studied. The studied alloys have large volume fractions and multimodal size distributions of the γ′ precipitates, making them sensitive to cooling conditions following solution heat treatment. Differential scanning calorimetry was conducted with a thermal cycle that replicated a processing heat treatment. The hardness of these alloys was subsequently evaluated by nanoindentation. The Nb/Ti ratio was not observed to influence the size and distribution of primary and secondary γ′ precipitates; however, the difference in those of tertiary γ′ and precipitate morphology were observed. The nanoindentation hardness for all alloys reduces once they have been solution-heat-treated. The alloys exhibited specific peak hardness. The alloy with the greatest Nb content was found to have the best increase in hardness among the alloys studied due to its large tertiary γ′ precipitate.