Fe-based metallic glasses are distinguished by high mechanical strength, good corrosion resistance and reasonable price, but due to limited ductility cracks often appear during thermal processing ...like laser cladding. This problem is especially visible when several beads are deposited. Therefore, an alloy with increased ductility was selected for tests to check if it can facilitate cladding of defect-free coatings. The alloy was gas atomized and then sieved to desired fraction. The coatings were then deposited with laser cladding. The obtained coatings were fully crystallized with microstructure varied from dendritic to globular one and strong segregation of the phosphorous and molybdenum.
•The (Fe0.9 Co0.1)76Mo4(P0.45C0.2B0.2Si0.15)20 at.% metallic glass was laser cladded onto ARMCO Iron plate.•Fully crystallized coatings were obtained despite the presence of 75% amorphous phase in the powder.•The microstructure varied from dendric to globular depending on the energy input.•The phosphorous segregated strongly in the coating forming a hard phase at the grain boundaries.
The plasma electrolytic oxidation is an innovative method for the surface treatment of titanium and its alloys. This review provides an overview of the historical development of the process and ...summarizes the current state of the art. The chemical as well as the electro- and plasma-chemical basics of the layer forming mechanisms, which comprises the substrate/electrolyte interface before discharge initiation and the different types and stages of plasma electrolytic discharge phenomena are explained within the context of titanium-based materials. How these phenomena can be influenced by the use of suitable electrolytes and controlled by the electrical regime is described. Subsequently, the microstructures and composition of the layers are described in detail, and the properties for specific applications are then discussed. The resistance of a PEO coating to corrosive environments, tribological factors, and alternating mechanical stress is viewed critically, and the extensive functional properties such as physiological compatibility, photocatalytic activity, and decorative properties are revealed. Finally, examples of various practical applications in the medical engineering, aviation, automotive, and environmental technology fields, as well as other branches of industry, are presented.
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Alumina is an important material for thermal spray coating solutions. For improving the coating properties, additions of TiO2 or Cr2O3 are common, but their simultaneous addition has not been studied ...so far. One alumina-rich ternary feedstock powder composition (81 wt% Al2O3−12.5 wt% Cr2O3–6.5 wt% TiO2) was prepared in three different ways: 1) blending of commercial fused and crushed plain oxide powders; 2) blending of two commercial binary jointly fused and crushed feedstock powders (Al2O3–13 wt% TiO2 and Al2O3–25 wt% Cr2O3); 3) preparing an experimental agglomerated and sintered powder. Plain oxide powders and the two binary powders were used for comparison. The feedstock powders were studied by a standard procedure, including particle size distribution by laser diffraction, the morphology and microstructure by SEM and EDS, and phase composition by XRD. Coatings were prepared by APS with an Ar-H2 plasma gas mixture, using a single spray parameter set optimized for the plain Al2O3 powder. The influence of the feedstock powder properties on coating deposition was evaluated by the average thickness per layer and coating roughness. The coating microstructures were studied by optical microscopy and SEM, including the investigation of local compositions by EDS. The phase compositions and lattice parameters of the alumina phases in the powders and coatings were investigated by XRD. The coatings were characterized for their microhardness HV0.3, and tribological (unidirectional dry sliding wear resistance), corrosion (exposure testing against H2SO4) and electrical (resistivity, dielectric breakdown field strength and impedance) properties. Chromia additions, existing as a (Al,Cr)2O3 solid solution in the feedstock powder, were found to have a positive effect on the stabilization of the corundum phase for APS coatings, while titania additions were found to have no influence on the corundum phase stability. The corrosion resistance was found to be positively influenced by the joint addition of chromia and titania compared to plain alumina-
•Feedstock powders of the ternary composition Al2O3–12.5 wt% Cr2O3–6.5 wt% TiO2•Different manufactured feedstock powders were used (blends of plain oxides and binary oxides, agglomeration and sintering)•Strong influence of feedstock powder properties on the coating microstructure and properties•Cr2O3 partially stabilized the corundum phase•High wear and corrosion stability with adaptable DC resistance for ternary composition
Amino-silane coupling agents are used to improve adhesion to polyamide-based composites. This paper aims to study the influence of polyamide 6 moisture content on the interfacial strength between the ...polyamide and amino-silane-coated aluminum. A coupled experimental and simulative approach is applied that enables the interfacial strength to be taken separately from the moisture-dependent mechanical behavior of polyamide 6. Lap joints of polyamide 6 and aluminum, functionalized by 3-(2-aminoethylamino)propyl trimethoxy silane, are tested at three different polyamide moisture conditions. Afterwards, numerical simulations of the lap shear experiments are carried out to identify the parameters for a mechanical model of the interface. Subsequently, the dependence of polymer's properties on the moisture content is investigated by different sets of parameters of an applied inelastic material model. Finally, an analysis of the interfacial parameters proves and characterizes the dependence of the joint strength on polyamide moisture content. It is found that the lower the moisture content of the polyamide, the higher the interfacial strength.
Basic research has been done on diffusion-welded joints with the overall aim of an adjusted interface design. The phase formation of aluminium alloy/magnesium alloy bonds has been revealed by X-ray ...diffraction, energy-dispersive spectroscopy and electron back-scatter diffraction. The presence of Al
12
Mg
17
and Al
3
Mg
2
phases in a bi-layer has been confirmed. The distribution and microstructure of the formed intermetallics and the arrangement of the precipitates originating from the alloys have been determined. Precipitates originating from the alloys agglomerate in the bi-layered welding zone. Their arrangement in combination with the grain boundary evolution of the intermetallics and the change of the aluminium base solid solution in the interface region has a significant influence on the mechanical properties of the joint.
The present work was planned to investigate the microstructural evolution and mechanical properties of a metastable β-type titanium alloy composing of Ti–27.96Nb–11.97Ta–5.02Zr %wt (so-called TNTZ ...alloy), after applying a predetermined low-temperature thermomechanical processing (LTMP) cycle. The room temperature uniaxial tensile testing was utilized to evaluate the processed material flow behavior. To this end, the occurrence of any phase transformation and twinning-induced elasto-plasticity effects along with the work hardening behavior of the experimental TNTZ alloy were thoroughly studied. A double yielding phenomenon was realized in the specimens subjected to cold rolling and subsequent short time annealing. The XRD analysis confirmed an increase in volume fraction of α″ martensite as a result of deformation-induced martensite transformation in the microstructure. Electron backscatter diffraction (EBSD) analysis revealed that low angle boundaries would form within grains holding near (001) texture and might well act as a preferred nucleation site to develop deformation-induced martensite. The intersections of α″ martensite and the contribution of dynamic Hall-Petch effect could result in spectacular work hardening behavior in comparison to other β-type titanium alloys. The presence of sub-sized grains in the microstructure was related to the martensite reversion; this could further increase the strain hardening rate in the experimental alloy.
The strain-controlled fatigue and near-threshold fatigue crack growth behavior of an ultrafine-grained (UFG), age-hardening aluminum alloy after severe plastic deformation by equal-channel angular ...pressing (ECAP) are discussed. The main question addressed is how different precipitate morphologies affect low-cycle fatigue (LCF) and fatigue crack growth. An AlMg0.5Si0.4 alloy is subjected to two and eight passes of ECAP to obtain different degrees of grain refinement and fragmentation of the initially semi-coherent precipitates. Furthermore, a thermally recovered condition with newly formed, small coherent precipitates, which is obtained by aging after two ECAP passes, is considered. Strain-controlled fatigue tests and Delta K-controlled crack growth measurements are conducted and microstructural evolution during cycling and fracture surfaces are carefully analyzed using scanning and transmission electron microscopy. Most importantly, the results of this study show that newly formed, coherent precipitates in the thermally recovered condition directly contribute to a more planar slip behavior, to slip localization and to early failure during LCF loading. It is clearly demonstrated that precipitate morphology also affects fatigue crack propagation, and that this is closely related to slip reversibility, even in the UFG regime.
The austenitic stainless steel 316L is used for numerous components due to its excellent corrosion resistance. However, forming of components influences the microstructure and can thus change the ...corrosion resistance of the steel. In this context, the corrosion rate of the steel 316L is determined for the case of uniform corrosion of various cold-rolled conditions by ageing tests in 0.5 M H
2
SO
4
. The microstrain, the martensite fraction, and the residual stress state are quantified using X-ray diffraction. The surface roughness is measured by laser scanning microscopy. Three different model equations are derived by means of multiple regression to predict the corrosion rate as a function of the specimen properties. The analysis shows that a particularly simple model equation, which predicts the corrosion rate only via the plastic strain, shows insufficiently large deviations from the experimentally determined corrosion rates. However, a low divergence to the experimental results with a mean deviation of less than 4% is achieved by using a model equation that takes microstructural parameters and the surface ratio into account. Within this model equation, an increased corrosion rate is achieved with higher microstrain and residual compressive stress of the austenite phase as well as a higher surface-area ratio. A higher fraction of martensite is found to lower the corrosion rate.
Quenching and partitioning (Q&P) treatments result in promising mechanical properties of advanced high-strength steels. However, recent studies indicate that Q&P steels are very susceptible to ...hydrogen embrittlement (HE). Using slow strain-rate tests, the effects of hydrogen charging in different media without and with recombination poison were investigated for Fe-0.38C-1.92Si-0.66Mn-1.39Cr in quenched and tempered as well as Q&P conditions. In addition, corrosion tests and Zn electroplating of tensile specimens were performed. In both heat-treatment states, it was found that the intensified hydrogen-charging conditions using a recombination poison strongly impact the result of HE investigations: HE only occurs when a recombination poison is present. In addition, the negative influence of hydrogen formed during Zn electroplating can be limited by using proper electrolytes and electrical parameters. This allows keeping the HE susceptibility of the Q&P steel low in practical applications when recombination poisons are absent.
Selective laser melting (SLM) is one of the promising techniques for producing metallic glass components with unlimited geometries and dimensions. In the case of iron-based metallic glasses, the ...appearance of cracks remains a problem. In this work, two alloys Fe
48
Mo
14
Cr
15
Y
2
C
15
B
6
and (Fe
0.9
Co
0.1
)
76
Mo
4
(P
0.45
C
0.2
B
0.2
Si
0.15
)
20
, differing in their plasticity, were printed with a double stage scanning strategy. Both alloys were characterized by a fully amorphous structure and a crack grid that coincided with the hatch distance in the first scan. Segregations of metalloids were observed in the vicinity of the cracks. Fe
48
Mo
14
Cr
15
Y
2
C
15
B
6
samples were characterized by a high compression strength of 1298 ± 11 MPa and zero plasticity. The compression strength of the (Fe
0.9
Co
0.1
)
76
Mo
4
(P
0.45
C
0.2
B
0.2
Si
0.15
)
20
samples was 142 ± 22 MPa. The results obtained suggest that further development of scanning strategies and research on the influence of alloying elements is needed.
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