Advanced Engineering Materials

The cover illustrates a new synthetic strategy to prepare biobased engineering elastomer (BEE), which might be a substitute for some traditional synthetic rubber, from renewable biomass feedstock, and a reduced cost approach to fabricate the BEE nanocomposites as well as some final products made from BEE. Further details can be found in the article by P. Coates et. al. on page 112.

Self-assembled nanoparticle aggregates with spherical shape using inkjet printing (colorized SEM image by digital image processing). Further details can be found in the article by E. Sowade et. al. on page 98.

Solid state refrigeration requires improvements of magneto-, elasto-, baro-, and electro-caloric materials. In this paper we sketch the potential and challenges for introducing the giant entropy changes associated with ferroelastic phase transformations in practical cooling applications: energy efficiency, effect size, and fatigue behavior. The figure exemplarily sketches a barocaloric cooling cycle.

Composites consisting of magnetic shape memory particles and a polymer matrix combine the advantages of both material classes: the high achievable magnetic field induced strain (MFIS) of Ni-Mn-Ga with a ductile matrix. We investigate important parameters like the stiffness of the polymer matrix as well as the particle-matrix interface. In Ni_50.9Mn_27.1Ga_22.0 epoxy composites, a MFIS of 0.1% is observed and is resettable by rotating the magnetic field by 90°.

Magnesium alloys based on AZ91 or ZEK200 together with samarium–cobalt are investigated. An Mg alloy with magnetic characteristics and satisfactory mechanical properties, which can be utilized as a lightweight sensor material, is produced by die casting. Inverse magnetostriction is exploited in order to verify the instantaneous operating forces in structural components made from magnetic Mg.

Plastic deformation of Al–3Mg alloy after three ARB-cycles at RT is investigated in temperature range from 0.5 to 295 K. Potrevin–Le Chatelier effect occurs at RT and with decreasing temperature from 77 to 20 K, the deformation curves begin to be smooth. Nevertheless, the low-temperature serrated deformation (LTSD) is found at 4.2 and 0.5 K.

A way to manufacture aluminum sheets of commercial purity with a strong Cube texture is to partially recrystallize and slightly roll the alloy before final recrystallization. After 10% cold-rolling, the microstructure recovery is studied using FEG/EBSD in situ heating. Cube nucleation occurs by sub-grain growth and Cube growth is enhanced thanks to the difference of stored deformation energy between these Cube nuclei and their non-Cube neighbors as observed by TEM.

This work presents a novel in situ reaction approach to produce Al matrix composites from a powder mixture of Al/5 wt% Fe₂O₃ by using selective laser melting (SLM). The SLM process is able to produce three-dimensional parts besides activating in situ reaction in the powder mixture, creating hard particles to reinforce Al matrix. These particles are distributed uniformly with good particle/matrix interface.

New experimental results using different prestrains and different recovery durations highlight an efficient metallurgical route to produce single phase steels with high combination between yield stress and strain-hardening. This is achieved by exploiting the thermal stability of mechanically induced twins in a high manganese austenitic Twining Induced Plasticity alloys.

Square cell honeycomb structures with TRIP-steel/MgO partially stabilized zirconia composite material have been produced by extrusion technique. Compressive deformation tests with low strain rate have been performed to evaluate the influence of mixture on mechanical properties. The microstructure and phase evolution under load are studied by SEM and EBSD.

The thermo-mechanical behavior of a novel Fe–Mn–Si–Cr–Ni–VC shape memory alloy produced using standard air casting facilities is characterized as well as in the hot forged and cold rolled state. Beside a certain pseudoelasticity, the alloy shows good shape recovery properties and remarkably high shape memory stresses after heating to temperatures of only 160°C, making the alloy interesting for applications that make use of the shape memory effect.

A series of Mg-Zn-Al-RE magnesium alloys with different combinations of Zn and Al contents were prepared by high pressure die casting. The HTS and mechanical properties have been investigated by incorporating the work on Mg-4Al-4RE and Mg-Zn-Al alloys. This paper suggests the relationships between alloy composition, HTS and tensile properties of Mg-Zn-Al-RE alloys.

The absorption of nitrogen in Al-alloy composites during cryomilling and the mechanism invoke great research interest. The results from the molecular dynamics simulation function in Materials Studio® software indicate that Mg solute atoms in the matrix tend to segregate to Al/Al₂O₃ interfaces, creating vacancies in the Al lattice and subsequently enhancing the absorption of nitrogen into the Al lattice.

The formation of Ti₂SnC MAX phase by pressureless infiltration of Sn melt into TiC0.5 is shown. The carbide is prepared by mechanical synthesis at RT. Due to mechanical activation the synthesis temperature of MAX phase formation is reduced compared to results reported on elemental mixtures.

A distinctive difference in phase morphology and texture of the microstructure is noticed between the selective laser molten (SLM) and vacuum arc remelted (VAR) Ti6Al4V. The fine acicular martensite phase of the SLM-Ti results in more brittle behavior and inferior fracture toughness. On the other hand, the fine grained microstructure leads to a large number of grain boundaries acting as obstacle points for crack propagation, leading to acceptable crack growth rates.

This paper demonstrates a novel process for the fabrication of three-dimensional, highly symmetric aggregates consisting of a variety of nanospheres. The manufacturing process is based on inkjet printing with an adapted control signal. It enables the formation of spherical aggregates in a dry environment and independent of the substrate surface properties.

Two silver complexes are evaluated as lubricant additives by friction and wear measurements. Thermo-elastohydrodynamic simulations provide guidelines for test parameters to promote thermal decomposition of these silver complexes. These two complexes undergo thermolysis to produce surface metallic silver coatings in the wear region, thus significantly reducing wear.

In this study, we describe the fabrication of micrometer concentric ring structures on polymer substrate using an axicon and high power pulsed ultra violet laser radiation. The fabrication method consists on producing a periodic intensity distribution over the polymer's surface with a Bessel beam shape. This simple optical arrangement can be used to fabricate such periodic structures over several square millimetres.

Large-scaled monomers derived from biomass feedstock are chosen to generate the first synthetic bio-based engineering elastomer (BEE) and BEE nanocomposites. Because of BEE's polarity and the existence of hydrogen bonds, silica nanoparticles disperse well in the BEE matrix to achieve significant strengthening and environmental stability. Further chemical crosslinks effectively suppress the crystallization, and increase the elasticity along with physical and mechanical properties. Thus, BEE nanocomposties exhibits excellent comprehensive thermomechanical properties.

Tuning elastic properties of open-cell foam-like structures without changing the solid volume fraction is a challenge for material science, of particular relevance for the design of rapid-prototyped artificial bone scaffolds. We present a method, based on randomizing vertex connectivity, which allows to tune mechanical stiffness of a network structure over a substantial range with only marginal changes in solid volume fraction or pore geometry.