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:

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.

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...

The Al x CoCrCuFeNi alloys with multiprincipal elements (x ϭ the aluminum content in molar ratio, from 0 to 3.0) were synthesized using a well-developed arc-melting and casting method, and their mechanical properties were investigated. These alloys exhibited promising mechanical properties, including excellent elevated-temperature strength and good wear resistance. With the addition of aluminum from x ϭ 0 to 3.0, the hardness of the alloys increased from HV 133 to 655, mainly attributed to the increased portion of strong bcc phase to ductile fcc phase, both of which were strengthened by the solid solution of aluminum atoms and the precipitation of nanophases. The alloys exhibited superior high-temperature strengths up to 800 °C, among which the Al 0.5 CoCrCuFeNi alloy, especially, had enhanced plasticity and a large strain-hardening capacity. Moreover, the wear resistance of these alloys was similar to that of ferrous alloys at the same hardness level, while the alloys with lower hardness exhibited relatively higher resistance because of their large strain-hardening capacity.

Thermal-spray technology is commonly used for structural components by building up a protective coating layer on their surfaces. Choosing a suitable sprayed metal can improve corrosion resistance, [1,2] oxidation resistance, [3±5] wear resistance [6] and/or heat insulation, and thus extend the life of protected components.Three methods have been developed to give a protective coating to resist oxidation: glass-ceramic coating, [7±11] aluminiding the surface by reaction between Al and metal substrates, [12±15] and over-layer coating such as MCrAlY (M=Fe, Co, Ni) superalloys. [16±21] Glass-ceramic or aluminide layers are hard and brittle at low temperatures, and easily delaminated from the substrate due to the mismatch of the coefficient of thermal expansion. Over-layer coating of MCrAlY alloys is the favorite one for industry to protect structural components from oxidation at high temperatures. However, its lower hardness, about HRC 20~30, renders them poor in wear resistance when particulates or counterparts are involved in the environment. Thus, traditional coating materials can not provide an ideal coating both for oxidation resistance and wear resistance. In this study, a new alloy design concept ª;multi-principle-element alloysº, was explored to create alloys with excellent combinations of properties for some critical applications such as dies, molds and turbine blades. Processing, microstructure and properties were investigated to evaluate such multi-principle-element alloys as AlSiTiCrFeCoNiMo 0.5 (designated as 8E) and AlSiTiCrFeNiMo 0.5 (designated as 7E).As-cast microstructure and properties: Figure 1 shows the XRD patterns of as-cast 8E and 7E alloys. It reveals that their microstructures consist primarily of an ordered BCC phase and two FCC phases. The ordered BCC phase of 8E alloy had a lattice constant a = 2.87 , and the two FCC phases had a = 3.52 and 4.14 , respectively. 7E alloy had the phases with nearly the same constants as 8E alloy. It is indeed a surprise to see that these alloys did not to have many complex phase constituents since many possibilities of binary or ternary phases might be expected for such a large number of principle elements. Figure 2 shows the SEM pictures of the as-cast microstructures of 8E and 7E alloys. They were of a typical dendritic cast structure. EDS analysis indicates that Si, Ti, Cr, Fe, and Co and Mo were the main elements in the dendrite whereas Ni and Al were the main elements in the interdendrite regions. It is interesting to see that Co played as a neutral element and partitioned almost equally in both regions. The dendrite phase corresponded to the BCC phase shown in the XRD pattern and the interdendrite one was related with the FCC phases since the former was rich in Mo and Cr elements both of which have the BCC structure and are the first two elements highest in melting point. COMMUNICATIONS 74