Dear Readers, Welcome to the first issue of Advanced Engineering Materials in 2015. Times are changing and so does the field of engineering materials. However, one trend remains the same-we receive more and more submissions each year. Over the last three years the number of submissions has increased by 75%. Such an enormous growth in submissions means thatweare forced tobecome even more selective,sothe rejectionrateisincreasing accordingly. At the sametimeweaim at providing decisions as fast as possible and have reduced the average time it takes to receive an initial decision to below 30 days Since January 2014 AEM is published online only. One year later we can say that this change is seen very positive throughout the community. Especially the fact that color reproduction of figures is now free has been welcomed by our authors. Advanced Engineering Materials publishes manuscripts from a variety of fields, such as metal foams, bulk metallic glasses, advanced ceramics, alloys, metals, and polymers for a diversity of possible applications. Our authors discuss novel design concepts and new ways to analyze materials properties, including both experimental and modeling approaches. This broad range of topics is also reflected in the list of the most accessed articles in 2014 given in Table 1. Finally, it is my pleasure to welcome the following high-ranking scientists to the advisory board:

High-entropy alloys (HEAs) are alloys with five or more principal elements. Due to the distinct design concept, these alloys often exhibit unusual properties. Thus, there has been significant interest in these materials, leading to an emerging yet exciting new field. This paper briefly reviews some critical aspects of HEAs, including core effects, phases and crystal structures, mechanical properties, high-temperature properties, structural stabilities, and corrosion behaviors. Current challenges and important future directions are also pointed out.

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A new approach for the design of alloy systems with multiprincipal elements is presented in this research. The Al x CoCrCuFeNi alloys with different aluminum contents (i.e., x values in molar ratio, x ϭ 0 to 3.0) were synthesized using a well-developed arc-melting and casting method. These alloys possessed simple fcc/bcc structures, and their phase diagram was predicted by microstructure characterization and differential thermal analyses. With little aluminum addition, the alloys were composed of a simple fcc solid-solution structure. As the aluminum content reached x ϭ 0.8, a bcc structure appeared and constructed with mixed fcc and bcc eutectic phases. Spinodal decomposition occurred further on when the aluminum contents were higher than x ϭ 1.0, leading to the formation of modulated plate structures. A single ordered bcc structure was obtained for aluminum contents larger than x ϭ 2.8. The effects of high mixing entropy and sluggish cooperative diffusion enhance the formation of simple solid-solution phases and submicronic structures with nanoprecipitates in the alloys with multiprincipal elements rather than intermetallic compounds.

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Crystalline solid solutions are typically formed in conventional alloys based on one or two host elements. Here, in this research, four alloys containing multiprincipal metallic elements (Ն5 elements) were prepared by casting, splat quenching, and sputtering. Their microstructures and crystal structures were investigated. It was interestingly found that solid solutions with simple fcc or bcc crystal structure were also practically formed in these alloys with multiprincipal elements. All different atoms are regarded as solutes and expected to randomly distribute in the crystal lattices without any matrix element defined.An ideal crystal structure is regarded as a superposition of a basis (an atom, or a group of atoms or ions) on a periodical framework, called a Bravais lattice. [1][2][3][4][5][6] Even though real crystals have point defects, such as vacancies and solute atoms, the phases of metallic alloys are known to have crystal structures, consistent with Bravais lattices, excluding quasi-crystals with fivefold symmetry. [3][4][5][6][7][8][9] Table I lists examples of metallic elements. [3,4,5] Their crystal structures normally fall into three main categories-fcc, bcc, and hcp. Most conventional alloys of crystalline solid solutions studied to date are based on one or two host elements, [10,11,12] raising the question of whether other crystalline solid-solution alloys with multiprincipal elements (more than the lattice points per unit cell) exist. Based on the general understanding of physical metallurgy and phase diagrams, abundant formation of intermetallic compounds or ordered phases is anticipated when multiprincipal elements are added into the alloys. [12] The complexity of such microstructures is expected not only to be responsible for their brittleness, but also for difficulties in processing and analysis. This fact has discouraged the design of new alloys with multiprincipal elements.However, solid solutions with multiprincipal elements tend to be thermodynamically stable because of their high mixing entropies. [13,14] Determining whether the alloys with multiprincipal elements could also crystallize into a simple Bravais structure would also be of interest. Some studies have developed a new approach to design alloys with multiprincipal metallic elements (Ͼ5 elements) in equimolar or near-equimolar ratios to exploit fully the high mixing entropy of the solid-solution state. [15][16][17][18] In this investigation, four alloys of multiprincipal metallic elements were prepared by different methods; solid solutions with simple fcc or bcc structures were also formed in alloys without detectable intermetallic compounds or ordered phases. No "matrix or host" element is defined, and all atoms are regarded as solutes, expected to be randomly distributed in the crystal lattices, according to a statistical average probability of occupancy.Four alloys that contain multiprincipal metallic elements were prepared by three methods-conventional casting, rapid solidification, and vacuum sputtering. Bulk CuCoNiCrFe, CuCo...