Al-Mg alloys are normally prone to lose part of their yield and tensile strength at high temperatures due to insufficient thermal stability of the microstructure. Here, we present a Ca-modified Al-Mg-Sc alloy demonstrating high strength at elevated temperatures. The microstructure contains Al 4 Ca phases distributed as a network along the grain boundary and Al 3 (Sc,Zr) nano-particles dispersed within the grains. The microstructure evolution and age-hardening analysis indicate that the combination of an Al 4 Ca network and Sc-rich nano-particles leads to excellent thermal stability even upon aging at 300 °C. The tensile strength of the alloy for temperatures up to 250 °C is significantly improved by an aging treatment and is comparable with the commercial heat-resistant aluminum alloys, i.e., A356 and A319. At a high temperature of 300 °C, the tensile strength is superior to the above-mentioned commercial alloys, even more so when expressed as the specific strength due to the low density of Ca-modified Al-Mg-Sc alloy. The excellent high-temperature strength results from a synergistic effect of solid solution strengthening, grain boundary strengthening and nanoparticle order strengthening.
Stealth technology is critical for the existence and the employment of the modern combat weapons systems. Electrochromic materials, which are known as a kind of novel intelligent stealth materials with multi-coloring effect under dynamic control, shows reversible color and emittance change under applied electric filed. Current emerging EC technologies utilizing electrochromism being widely used in intelligent stealth to produce more enhanced effects than traditional static options. This review mainly discusses recent advancement in the electrochromic materials with focus on its applications in the intelligent stealth technologies. Firstly, the principle and classification of electrochromic materials are presented along with summary of recent developments in electrochromism. Secondly, the potential applications of inorganic and organic electrochromism in visible and infrared stealth bands are highlighted. Finally, the challenges and further development approaches are emphasized; it will be intended to underline the future perspectives in realizing intelligent stealth for different applications.
The mechanical properties are strongly associated with the heat treatment applied in the Al–Cu–Mg alloys. The peak aging treatment is normally employed following solution treatment to achieve a peak aging hardening effect. However, herein, it is shown that the creep resistance is improved at under‐aged (UA) conditions, where the material is transiently weaker than that at peak condition. Under the creep condition of 185 °C and 150 MPa, the creep fracture time of the UA (4 h) alloy is the longest at 146.5 h, followed by 128 h of the peak‐aged alloy and 72 h of the over‐aged alloy. The stress exponents are about 4, which indicates that the creep deformation mechanism of the alloy is mainly due to fracture caused by dislocation slip and grain boundary (GB) migration. Combined with the first‐principles calculation, the reason for the longer creep fracture time of the UA alloy is that the solutes Cu and Mg retained in the UA alloy interact with GBs and dislocations during creep.
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