Multi-principle element alloys have enormous potential, but their exploration suffers from the tremendously large range of configurations. In the last decade such alloys have been designed with a focus on random solid solutions. Here we apply an experimentally verified, combined thermodynamic and first-principles design strategy to reverse the traditional approach and to generate a new type of hcp Al-Hf-Sc-Ti-Zr high entropy alloy with a hitherto unique structure. A phase diagram analysis narrows down the large compositional space to a well-defined set of candidates. First-principles calculations demonstrate the energetic preference of an ordered superstructure over the competing disordered solid solutions. The chief ingredient is the Al concentration, which can be tuned to achieve a D0₁₉ ordering on the hexagonal lattice. The computationally designed D0₁₉ superstructure is experimentally confirmed by transmission electron microscopy and X-ray studies. Our scheme enables the exploration of a new class of high entropy alloys.

Four different compositions of high entropy alloys based on Al–Co–Cr–Fe and Al–Co–Cr–Fe–Ni systems were prepared using mechanical alloying and consolidation by spark plasma sintering. The chemical compositions of the studied alloys were experimentally selected to obtain a BCC solid solution and mixtures of BCC with FCC. The microstructure of the Al25Co25Cr25Fe25 (all in at%) high entropy alloy consisted of a matrix with a high concentration of Al, Co and Fe, in which spherical grains (50–200 nm) enriched in Cr were embedded. Both the matrix and grains had body centered cubic structures. The addition of nickel to a four-element system led to the formation of a multiphase composition. The microstructure of the Al20Co20Cr20Fe20Ni20, Al10Co30Cr20Fe35Ni5 and Al15Co30Cr15Fe40Ni5 HEAs consisted of fine grains measuring 50–500 nm composed of: AlNi-B2, BCC phase, FCC or BCC solid solutions and σ-sigma phase, respectively. The complex structure of the studied samples resulted in changeable mechanical properties. The highest compression strength of 3920 MPa was accompanied by an increased yield strength of 3500 MPa, and a low strain of 0.7%, for the Al25Co25Cr25Fe25 alloy. The addition of Ni led to the formation of plastic FCC phases responsible for a decrease in strength with increases in ductility, which, in the new non-equiatomic Al10Co30Cr20Fe35Ni5 high entropy alloy reached 6.3% at a yield strength of 1890 MPa and compression strength of 2230 MPa. The conducted abrasion studies revealed that non-equilibrium high entropy alloys have the highest abrasion resistance.

Semi-solid metal processing (SSM) is a modern metal forming technology offering net-shape metal components of complex geometry in a one-step operation. The process relies on the thixotropic behaviour of metals with non-dendritic microstructures in a wide semi-solid temperature range. The beneficial effects are currently exploited in aluminium and magnesium alloys. This alternative manufacturing route to casting and forging has generated high expectations regarding high melting alloys, although no conclusive results have been achieved so far. Current studies focus on a deep understanding of the fundamental basics of alloys in the semi-solid range, e.g. rheology, microstructural evolution, and the consequences of forming, e.g. relations between process parameters, microstructure, and properties. This critical assessment aims at defining the important needs for further development of SSM, and assessing current knowledge.

Magnesium is particularly challenging material, when formed from liquid phase because of high flammability risk. An alternative process for casting, which eliminates above mentioned disadvantage, is thixoforming, which involves a lower temperature of process and operation in the partially solidified state. Influence of semi-solid metal processing on EZ33A magnesium alloy (Mg–Zn–RE–Zr) microstructure and mechanical properties was studied. Ingot microstructure revealed globular grains with coarse eutectic mixture consisting of Mg₇Zn₃RE, T-phase – RE(Mg,Zn)₁₁ and α(Mg). Heterogeneous nucleation of magnesium solid solution allowed obtaining structure appropriate for thixoforming. Using differential scanning calorimetry, temperature of process was determined to be 622 °C, which corresponded to about 30% of the liquid phase. Thixo-cast microstructure consisted of α(Mg) globular grains with a size of 76 ± 1.1 surrounded by fine eutectic mixture in a volume of 35%. T6 heat treatment (solution at 500 °C for 6 h and ageing at 190 °C for 33 h) caused increase of grain size to 92 μm and the precipitation of two kinds of phases within the α(Mg): ${{\beta }^{\prime }}_1$ and ${{\beta }^{\prime }}_2$ responsible for the increase of yield strength to 135 MPa, compression strength to 383 MPa and hardness to 73 HV₅.

The electron beam additive manufacturing process with wire is a part of global trend to find fast and efficient methods for producing complex shapes elements from costly metal alloys such as stainless steels, nickel alloys, titanium alloys etc. whose production by other conventional technologies is unprofitable or technically impossible. Demand for additive manufacturing is linked to the development of new technologies in the automotive, aerospace and machinery industries. The aim of the presented work was to carried out research on electron beam additive manufacturing with a wire as a deposited (filler) material. The scope of the work was to investigate the influence of selected technological parameters such as: wire feed rate, beam current, travelling speed, acceleration voltage on stability of the deposition process and geometric dimensions of the padding welds. The research revealed that, at low beam currents, the deposition process is unstable. The padding weld reinforcement is non-uniform. Irregularity of the width, height and straightness of the padding welds can be observed. At too high acceleration voltage and beam current, burn-through of plate and excess penetration weld can be revealed. The achieved results and gained knowledge allowed to produce, based on EBAM with wire process, whole structure from stainless steel.