Microstructure and Mechanical Properties of Magnesium Matrix Composites Interpenetrated by Different Reinforcement

The present work discusses the microstructure and mechanical properties of the as-cast and as-extruded metal matrix composites interpenetrated by stainless steel (Fe⁻18Cr⁻9Ni), titanium alloy (Ti⁻6Al⁻4V), and aluminum alloy (Al⁻5Mg⁻3Zn) three-dimensional network reinforcement materials. The results show that the different reinforcement materials have different degrees of improvement on the microstructures and mechanical properties of the magnesium matrix composites. Among them, magnesium matrix composites interpenetrated by stainless steel reinforcement have maximum tensile strength, yield strength, and elongation, which are 355 MPa, 241 MPa, and 13%, respectively. Compared with the matrix, it increases by 47.9%, 60.7% and 85.7%, respectively. Moreover, compared with the as-cast state, the as-extruded sample has a relatively small grain size and a uniform size distribution. The grain size of the as-cast magnesium matrix composites is mainly concentrated at 200⁻300 μm, whereas the extruded state is mainly concentrated at 10⁻30 μm. The reason is that the coordination deformation of reinforcement and matrix, and the occurrence of dynamic recrystallization, cause grain refinement of magnesium matrix composite during the extrusion process, thereby improving its mechanical properties. Moreover, the improvement is attributed to the effect of the reinforcement itself, and the degree of grain refinement of the metal matrix composites

Tribological Performance of Nanocomposite Carbon Lubricant Additive

In this research, nanocomposite carbon has been found to have excellent tribological properties as a lubricant additive. To reduce high friction and wear in friction pairs, the modified nanocomposite carbon has been prepared for chemical technology. The morphology and microstructure of the modified nanocomposite carbon were investigated via TEM, SEM, EDS, XPS, and Raman. In this study, varying concentrations (1, 3, and 5 wt. %) within the modified nanocomposite carbon were dispersed at 350 SN lubricant for base oil. The suspension stability of lubricating oils with the modified nanocomposite carbon was determined by ultraviolet-visible light (UV-VIS) spectrophotometry. The friction and wear characteristics of lubricants containing materials of the modified nanocomposite carbon were evaluated under reciprocating test conditions to simulate contact. The morphology and microstructure of the friction pair tribofilms produced during frictional contact were investigated via SEM, EDS, and a 3D surface profiler. The results showed that scratches, pits, grooves, and adhesive wear were significantly reduced on the surface of the friction pair which was used with 3% nanocomposite carbon lubricant. Additionally, the modified nanocomposite carbon showed excellent friction reducing and anti-wear performance, with great potential for the application of anti-wear

Investigation of the phase transformations in Ti-22Al-25Nb alloy

In this paper, changes in the morphology and composition of the O, α2 and B2/β phases and the transformation relationship between the three phases of Ti22Al25Nb alloy were systematically investigated by performing a series of short heat treatments. The results showed that the phase transformations can be divided into three stages in the temperature range of 870 °C ~ 1080 °C. In the first stage of 870 °C ~ 930 °C, the O phase started transferring to α2 + B2 first along grain boundaries with lamellar morphology due to short-range diffusion, and the O → α2 + B2 reaction was accompanied by a large amount of Nb segregation. With the increase in temperature, the phase transformation migrated from the boundaries to the inside of the grains, and the α2-phase spheroidized gradually. In the second stage from 960 °C to 1020 °C, granular α2 and B2 phases precipitated directly from the O phase due to long-range diffusion. At 1020 °C, the O → α2 + B2 transition was completed and the granular α2 phase mainly populated along the grain boundaries. In the third stage above 1020 °C, the main phase transformation was α2 → B2, and the aggregation and growth of the α2 phase were observed in α2-rich regions

Anticorrosion Properties of Zn–Al Composite Coating Prepared by Cold Spraying

In order to slow down the corrosion and wear of offshore equipment, the Zn–Al composite coating was prepared on Q345 substrate by cold spray technique. The mass fraction of Zn and Al in the raw material was 2:3. The microstructure of the original coating was observed by scanning electron microscopy (SEM) and was characterized by energy dispersive spectrometer (EDS). From the composite alloy coating obtained by cold spraying, it was observed that the Zn and Al particles were uniformly distributed without oxidation product, and the powder particles were significantly plastically deformed. The microstructure of the composite coating is very dense and has strong adhesion to the substrate. Neutral salt spray test (NSS) and electrochemical accelerated corrosion test results showed that Zn–Al composite coating can effectively provide corrosion protection

Effect of 0.8 at.% H on the Mechanical Properties and Microstructure Evolution of a Ti–45Al–9Nb Alloy Under Uniaxial Tension at High Temperature

To investigate the effect of hydrogen on the high-temperature deformation behaviors of TiAl-based alloys, the high-temperature tensile experiment was carried out on a Ti–45Al–9Nb (at.%) alloy with the H content of 0 and 0.8 at.%, respectively. Then, the effect of hydrogen on the high-temperature mechanical properties of the as-cast alloy was studied, the constitutive relations among stress, temperature, and strain rate were established, and the microstructure was analyzed. The results indicated that, compared with the unhydrogenated alloy, the flow stress of the hydrogenated alloy was significantly reduced, and the peak stress of the hydrogenated alloy decreased by (16.28 ± 0.17)% deformed at 1150 °C/0.0004 s−1. Due to the presence of hydride (TiAl)Hx in the alloy, the elongation showed a decline trend with increasing strain rate at the same deformation temperature. Compared with the unhydrogenated alloy, the elongation of the hydrogenated alloy reduced by (26.05 ± 0.45)% (0.0004 s−1), (23.49 ± 0.38)% (0.001 s−1), and (14.23 ± 0.19)% (0.0025 s−1), respectively, indicating that 0.8 at.% H softened the Ti–45Al–9Nb alloy and reduced the high-temperature plastic deformability. Under the same deformation condition, the deformation extent of the hydrogenated alloy was less than that of the unhydrogenated alloy. There were more residual lamellae in the hydrogenated alloy, and the extent of dynamic recrystallization was lower than that of the unhydrogenated alloy

Study on Corrosion Resistance and Wear Resistance of Zn–Al–Mg/ZnO Composite Coating Prepared by Cold Spraying

Two composite coatings, Zn65Al15Mg5ZnO15 and Zn45Al35Mg5ZnO15, were prepared by the cold spray technique and were found to be compact, with no pits or cracks, based on scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS) investigations. The results of the neutral salt spray (NSS) and electrochemical tests showed that the two composite coatings possess a suitable corrosion performance. However, the Zn45Al35Mg5ZnO15 composite coatings were more corrosion resistant and allowed a better long-term stability. In addition, they were found to exhibit the best wear resistance and photocatalytic degradation efficiency

Protective Performance of Zn-Al-Mg-TiO₂ Coating Prepared by Cold Spraying on Marine Steel Equipment

According to research, we have learned that zinc has excellent cathodic protection performance, that the corrosion products of aluminum and magnesium can form dense and stable passivation films to protect internal materials of coatings, and that TiO2 has excellent photocatalytic self-cleaning performance which will form a physical adsorption film on the surface to isolate the external corrosion solution. In this paper, a Zn-Al-Mg-TiO2 pseudo alloy coating was prepared by cold spray technique on a Q235 substrate. The protective performance of Zn-Al-Mg-TiO2 for marine metal equipment was studied using dynamic salt water corrosion testing, electrochemical testing, and friction and wear testing. The microstructure, composition, and wear marks of coatings were observed using a scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and white-light interferometer. The results show that the Zn-Al-Mg-TiO2 coating has excellent corrosion and wear resistance, which can provide long-term and stable protection for the substrate