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The Al-Si-Cu-Mg-Ni alloy is a commonly used piston alloy. In this work, different amounts of phosphorus modifier and Al-2P (Al-2%P) master alloy modifier were added to the original alloy. The ultra...

The effect of diamond surface pretreatment and content on the microstructure and mechanical properties of NiAl/Fe–x diamond (x=0,5,10,15,and 20 wt.%) alloys was investigated after mechanical alloying with subsequent hot-pressing sintering. The results showed that after the surface pretreatment, a complete transition layer containing W existed on the outer surface of the diamond grains, which improved the interfacial bonding strength of the diamond grains and NiAl/Fe matrix to an excellent level. As the diamond content increased, the compressive strength of the NiAl/Fe-based alloys declined, but the alloy with 10 wt.% diamond had a higher value than that of the other NiAl/Fe-based alloys. Short cracks and transgranular fracture were observed in the fracture surface of all materials. For the material with 20 wt.% diamond, intergranular fracture was obvious, and many diamond particles appeared along the fracture direction, which caused the compressive strength to be the lowest of the samples considered in this study. After the addition of diamond, the oxidation resistance of NiAl/Fe-based alloys decreased due to a loose oxidation layer and diamond graphitization. The thermal conductivity of the alloy first increased and then decreased with increasing diamond content. A NiAl/Fe-based alloy with 15 wt.% diamond demonstrated the maximum thermal conductivity of 53.2 W/(m·k) at 600°C among the samples in this study.

A Ti40Zr40Ni20 quasicrystal (QCs) rod and ribbons were prepared by conventional casting and rapid solidification. The X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and differential scanning calorimeter (DSC) techniques were used to investigate the microtissue, phase composition, and solidification features of the samples, the nano-indentation test was carried out at room temperature. The results show that a mixture of the α-Ti(Zr) phase and the icosahedral quasicrystal (I-phase) was formed in the Ti40Zr40Ni20 rod, the microstructure of Ti40Zr40Ni20 ribbons mainly consisted of the I-phase. The solidification mechanism of the I-phase was different in the two alloys. The I-phase in the quasicrystalline rod was formed by packet reaction while in the ribbons it was generated directly from the liquid. At room temperature, both samples had relatively high hardness and elastic modulus, the elastic modulus of the ribbons is 76 GPa, higher than the 45 GPa of the rod. The hardness of the ribbons was more than twice that of the rod.

Generally, well wear resistance corresponds to low friction coefficient. While, well wear resistance and high friction coefficient are needed in brakes for short braking distance and long serving life. Ceramics possess high hardness which correspond well wear resistance. Cobalt is often used as bond phase of tungsten carbide ceramic, which will increase the toughness of tungsten carbide. While, the stiffness of WC-Co will decrease after cobalt is introduced into tungsten carbide, which will lead to the decrease of friction coefficient. To increase the stiffness and the friction coefficient of WC-Co, nano WC particles were introduced into cobalt binder phase which formed WC-(nano WC-Co). In this work, WC-(nano WC-Co) coatings were prepared through high velocity oxygen fuel (HVOF) spray on the vermicular iron substrate in order to increase friction coefficient and wear resistance simultaneously. The microstructure, mechanical property and wear performance of the coating were investigated. It was found that the microhardness of WC-(nano WC-Co) coatings had the highest hardness of 1393 ± 13 HV with 50% nano WC-10Co-4Cr. Meanwhile, its friction coefficient was obviously increased to 0.7, which was three times higher than that of the vermicular cast iron and higher than both of the micro-sized and nano sized WC-Co. Its wear mass loss of WC-(nano WC-Co) coating was much lower than that of the vermicular cast iron and lower than both of the micro-sized and nano sized WC-Co. The friction coefficient and wear resistance of WC-(nano WC-Co) were increased simultaneously.

Al 7075 alloy, 15 wt.% VN/7075 composites, and 20 wt.% TiB2-TiCx/7075 composites were prepared by ball milling with subsequent hot-pressing sintering. The microstructure, hardness, and wear properties at room temperature to 200 °C of Al 7075-based composites with different reinforcement phases were discussed. The grain uniformity degree values of 15 wt.% VN/7075 composites and 20 wt.% TiB2-TiCx/7075 composites were 0.25 and 0.13, respectively. The reinforcement phase was uniformly distributed in 15 wt.% VN/7075 composites and 20 wt.% TiB2-TiCx/7075 composites, almost no agglomeration occurred. The order of hardness was 20 wt.% TiB2-TiCx/7075 composites (270.2 HV) &gt, 15 wt.% VN/7075 composites (119.5 HV) &gt, Al 7075 (81.8 HV). At the same temperature, the friction coefficient of 15 wt.% VN/7075 composites was the lowest, while the volume wear rate of 20 wt.% TiB2-TiCx/7075 composites was the lowest. With the increase of temperature, the wear mechanism of Al 7075 changed from spalling wear to oxidation wear and adhesion wear. However, the wear mechanisms of 15 wt.% VN/7075 and 20 wt.% TiB2-TiCx/7075 composites changed from abrasive wear at room temperature to wear mechanism (oxidation wear, abrasive wear, and adhesive wear) at medium and low temperature. Comprehensive wear test results indicated that 20 wt.% TiB2-TiCx/7075 composites had excellent tribological properties at medium and low temperature.

In this study, Fe-25Mn-xAl-8Ni-C alloys (x = 10 wt.%, 11 wt.%, 12 wt.%, 13 wt.%) were prepared by a vacuum arc melting method, and the microstructure of this series of alloys and the in situ tensile deformation behavior were studied. The results showed that Fe-25Mn-xAl-8Ni-C alloys mainly contained austenite phase with a small amount of NiAl compound. With the content of Al increasing, the amount of austenite decreased while the amount of NiAl compound increased. When the Al content increased to 12 wt.%, the interface between austenite and NiAl compound and austenitic internal started to precipitate k-carbide phase. In situ tensile results also showed that as the content of Al increased, the alloy elongation decreased gradually, and the tensile strength first increased and then decreased. When the Al content was up to 11 wt.%, the elongation and tensile strength were 2.6% and 702.5 MPa, respectively; the results of in situ tensile dynamic observations show that during the process of stretching, austenite deformed first, and crack initiation mainly occurred at the interface between austenite and NiAl compound, and propagated along the interface, resulting in fracture of the alloy.

The multi-arc ion plating technology is used to prepare CrN coating on the valve seat material surface. Results show that the surface grains gradually increase in size and becomes less uniform with the increase of the Cr target current. At different Cr target currents, the main phases of the CrN coating are Cr, CrN, and Cr2N. The critical load of the coating and matrix is 49.2 N. When the Cr target current is 65 A, the nano-hardness is maximum (18.84 GPa), and Young ’s modulus is 255.41 GPa. The CrN coating can reduce the friction coefficient of the valve seat material from 0.62 to 0.48, thereby improving the wear-resistance behavior. The main wear mechanism is abrasive wear.

T6 heat treated piston aluminium alloy (Al-13Si-4Cu-2Ni-1Mg-0.25Mn) were further aged at 350 °C and 420 °C, respectively, for various time (0–1000 h). The microstructures of the re-aged alloy were analyzed using optical microscope (OM, Nicon300) and transmission electron microscope (TEM, JEM-2010). The tensile strengths at room and 350 °C, as well as high cycle bending fatigue of the alloy were tested. The results show that the Al11Cu5Mn3 nanoparticles will precipitate during the elevated re-aging process. The volume fraction formed during re-aging at 420 °C is higher than that formed at 350 °C. Both room temperature (RT) and 350 °C tensile strengths, as well as the high cycle fatigue life of the alloy after being re-aged at 420 °C are higher than those of re-aged at 350 °C due to the notable precipitation strengthening effect of nano particles Al11Cu5Mn3.

In the present work, ribbon and 2-mm rod samples of Mg–Zn–Ca–Mn alloys were prepared by melt-spinning and copper mold injection methods, respectively. Effects of Mn doping on glass-forming ability and corrosion performance in simulated body fluid of Mg65Zn30Ca5 alloy were studied through X-ray diffraction, scanning electron microscopy, differential scanning calorimeter, and electrochemical and immersion tests. Results show that with the Mn addition increasing, all the ribbon samples are completely in amorphous state. However, the microstructure of 2-mm rod samples transfers from fully amorphous for the Mn-free alloy to almost polycrystalline state with precipitated Mg, Mn, and MgZn phases. Glass-forming ability of Mg65Zn30Ca5 alloy is decreased by Mn addition. Results of electrochemical and immersion tests demonstrate that the Mn-doped samples exhibit more negative corrosion potential and larger corrosion current density, suggesting that the corrosion resistance decreases with doping amount of Mn element increasing.

The creep behavior accompanying oxidation of a compacted graphite cast iron (CGI) containing Cu, Mo and Sn elements was studied at temperatures ranging from 350 °C to 550 °C and creep loads ranging from 40 MPa to 150 MPa. The creep damage was observed using both optical and scanning electron microscopy (SEM). The results showed that obvious creep deformation occurred when T / T m ＞0.5 ( T is testing temperature, T m is melting temperature of the CGI) and the load is higher than 150 MPa. The creep deformation in specimen was accounted from three parts: (I) deformation of matrix, (II) initiation and propagation of creep cavities and (III) debonding between graphite and matrix. In addition, two models of crack were observed during creep deformation: (I) cracks propagated preferentially in ferrite phase and combined with debonding between graphite and matrix and (II) creep microcracks caused by creep cavities in the grain boundary. These two types of crack are usually accompanied with oxidation and the former one is more harmful than the latter one because of high crack propagation rate accelerated by interfacial debonding indirectly. Finally, the mechanism of creep deformation and fracture was discussed.

The pore structure is of significance to both thermal barrier performance and compliance of plasma-sprayed thermal barrier coatings (TBCs). In order to tune the pore structure of plasma-sprayed TBCs, the heredity and variation of the hollow structure from hollow spherical powders (HOSP) to coatings were investigated. Different plasma arc powers were selected for spraying the ceramic coatings. The recollected powders sprayed into water were examined to reveal the microstructure of the powders after arc heating. The results showed that the HOSP structure of spray powder could be retained after heating in plasma arc. Therefore, these hollow structures could be retained into the coating. As a result, four types of pores were formed in the coating. The porosities of the coatings were decreased with the increase in the arc power. Therefore, low arc powers were more suitable to retain the HOSP structure into the coating.

A triphase composite ceramic coating, Al2O3–ZrO2 together with a small amount of SiO2 was successfully grown on a cast Al–12Si system piston alloy by a novel plasma electrolytic oxidation process with different zirconia sol additions in sodium silicate electrolyte. It was found that the compactness of the coating increased significantly and the hindrance of Si element on plasma electrolytic oxidation process was weakened effectively, and then the growth rate of the coating was improved substantially with zirconia sol addition. Meanwhile, Zr element was gradient distribution in the inner layer. Both the content of c-ZrO2 and the heat-insulating property of the coating increased significantly. After 1000 cycles of thermal shock, there is no cracking in the coating surface, which indicates that the plasma electrolytic oxidation coating with zirconia sol additions possessed a good thermal shock resistance.

Black microarc oxidation (MAO) ceramic coatings were prepared on TA2 pure titanium by adding the colorant [Cu(NH3)4]2+ to a Na2SiO3 base solution. The microstructures of the MAO coatings were characterized by scanning electron microscopy, energy dispersive X-ray spectrometry, and X-ray photoelectron spectroscopy. The corrosion resistance and wear resistance of the coatings were evaluated through potentiodynamic polarization and friction tests. [Cu(NH3)4]2+ was absorbed into the pores of the microarc discharge to form black copper oxide under high temperature and pressure. Cu content in the MAO coating increased with [Cu(NH3)4]2+ concentration. The wear resistance and hardness of the prepared black ceramic coatings were remarkably improved in terms of self-sealing microstructure. However, the corrosion resistance of the black coatings was approximately one or two orders of magnitude lower than that of the MAO coating without Cu doping. This study shows that the proposed method is a promising method for preparing decorative coating or absorbing light coating on a titanium surface.

In view of the failure of bearing bush due to their serious friction and wear and in order to improve deposition rate, Cp/AlSn self-lubricate coatings were prepared by magnetron sputtering/multi-arc ion plating. The coatings are uniform and Al, Sn and C elements are evenly mixed. With increasing of carbon target current, the grain sizes become smaller and smaller. The particles on the coating surface are “cobblestone-like”. The roughness decreases first and then increases with the increase of the carbon target current. The coating is composed of three layers. The working layer is equiaxed crystal mixed columnar crystal structure. The polycrystalline diffraction rings with Al and Sn elements have diffraction plane indexes of Sn Al (220) and Al (311), Sn (200) and Sn (211), respectively. The coating is of amorphous characteristic. Al and Sn elements exist in simple substance, and C element exists as graphite-like state with SP2 hybridization to form transfer film, improving the friction and wear performance. When the carbon current is 1.1 A, the bonding strength is 59 N, and the friction coefficient is 0.10. The Cp/AlSn coatings can improve the friction and wear performance of bearing bush.

The effects of cooling rate 0.15, 1.5, 15, 150, and 1.5 &times, 105 &deg, C/s on the microstructures and mechanical properties of Al-13Si-4Cu-1Mg-2Ni cast piston alloy were investigated. The results show that with an increase of solidification cooling rate, the secondary dendrite arm spacing (SDAS) of this model alloy can be calculated using the formula D = 47.126v &minus, 1/3. The phases formed during the solidification with lower cooling rates primarily consist of eutectic silicon, M-Mg2Si phase, &gamma, Al7Cu4Ni phase, &delta, Al3CuNi phase, &epsilon, Al3Ni phase, and Q-Al5Cu2Mg8Si6 phase. With the increase in the solidification cooling rate from 0.15 to 15 &deg, C/s, the hardness increased from 80.9 to 125.7 HB, the room temperature tensile strength enhanced from 189.3 to 282.5 MPa, and the elongation at break increased from 1.6% to 2.8%. The &epsilon, Al3Ni phase disappears in the alloy and the Q phase emerges. The &delta, phase and the &gamma, phase change from large-sized meshes and clusters to smaller meshes and Chinese script patterns. Further increase in the cooling rate leads to the micro hardness increasing gradually from 131.2 to 195.6 HV and the alloy solidifying into a uniform structure and forming nanocrystals.

The microstructure, texture and mechanical properties of extruded Mg–5Al–2Nd–0.2Mn alloy were investigated in the present work. The extruded alloy demonstrated a near-completely recrystallized grain structure with average grain size of about 20 μm. Intermetallic phases Al 11 Nd 3 and Al 2 Nd were fragmented to small particles and a small amount of Mg 17 Al 12 phase was precipitated during extrusion, which promoted grain refinement during dynamic recrystallization. A strong basal texture was formed with the basal plane parallel to the extrusion direction (ED) of the plate. The tensile strength was obviously improved after extrusion, and the difference in tensile strength of the extruded alloy in ED and transverse direction (TD) was obscure. However, the elongation in ED was higher than that in TD at both room temperature and 150 °C. It was resulted from the distribution of secondary phases along ED and basal plane texture tilting toward ED in the extruded alloy. The significant improvement in strength of the extruded alloy, compared with that of the as-cast alloy, was due to the grain refinement, the fragment of Al–Nd intermetallics, the increased interaction between the Al–Nd intermetallics and grain boundaries as well as dislocations, solid solution strengthening and texture strengthening.

The microstructure evolution of Mg–6 wt% Gd–2 wt% Y alloy (denoted as GW62) during solid solution and aging process were investigated by optical microscope, scanning electron microscope, energy dispersive spectroscopy, X-ray diffraction and high resolution transmission electron microscopy. The microstructure of as-cast GW62 alloy is comprised of isometric α(Mg) crystals, equilibrium phase Mg 5 (Gd,Y), and non-equilibrium phase Mg 2 (Gd,Y). With the increase of solution treatment time, the sizes of the semicontinuous Mg 5 (Gd,Y) phases gradually decrease until dissolved. Rare-earth-rich phases (Mg(Gd,Y) 2 ) with fcc structures a =0.56 nm were newly generated in the alloy at grain boundaries and inside grains after solution treatment, which could hinder the growth of isometric α(Mg) crystals in the solution process. The maximum hardness of the GW62 alloy is significantly different for different aging temperatures. The age-hardening effect is most apparent at 175 °C. The microstructural evolution of the alloy after aging at 175 °C was as follows: the β″ phase precipitated from α(Mg) during the under-aging stage (4–32 h); next, the β′ phase precipitated from α(Mg) up until peak aging was reached (32–100 h); as aging time progressed, the hardening reached its maximum at 100 h. At this stage, the precipitated phases were the β′ and β″ phases; finally, during over-aging (>100 h), the size of β′ phase continually increased while transforming into the β 1 and β phases.

In this paper, diamond-like carbon (DLC) films doped with CrN nano-crystalline were prepared on 316L stainless steel using a hybrid beam deposition system (including a linear ion source (LIS) and a DC magnetron sputtering of Cr target). The microstructure and composition of the films were studied using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Mechanical and tribological properties were investigated using nano-indentation and tribological tester. The results showed that an N doping could significantly influence the microstructure and properties of the as-deposited films. On one hand, the N atoms doped in the film tended to form Cr–N, –C N–H and C–N bonding, which would enhance the binding strength. On the other hand, the formation of CrN/CrC nano-crystalline due to N doping dispersed in the amorphous DLC matrix could play an important role and increase its hardness. In addition, the (Cr:N)-DLC showed low friction coefficient and wear rate compared with the Cr-DLC film.

In order to improve the room temperature ductility and high temperature strength of Fe-25Al alloys, in situ 20 wt.%Al2O3/Fe-25Al composites with 0, 1, 2, 3, 4, and 5 at.% Cr element contents (0-6.70 wt.%) were prepared by mechanical alloying inducing self-propagating reaction with subsequent plasma-activated sintering. Microstructures, room temperature hardness, flexural strength, fracture toughness, and compression property and wear behavior at mid-high temperatures of the sintered samples were tested and analyzed. The results showed that all the composites with Cr element addition had good microstructure with fine grain size and high relative density. The flexural strength and fracture toughness increased first and then decreased with increasing content of Cr. Especially, the composites with 3 at.% Cr had the highest flexural strength, highest fracture toughness, and best compressive properties during 298-1073 K, and the main fracture mechanism changed from brittle fracture at room temperature to plastic deformation and pullout of the second phase at 673 K. With Cr content increasing, the friction coefficients decreased and the wear rates increased because of decreasing hardness. The composites with 3 at.% Cr had excellent wear properties with lower friction coefficient and wear rate.

ZrO2-Y2O3 ceramic coating was produced by plasma electrolytic oxidation (PEO) on ZAlSil2Cu3Ni2 alloy. The microstructure and phase composition of the coating were investigated by SEM and XRD. The results show that adding an appropriate amount of yttrium ion can improve the growing rate of ceramic coating at different oxidation stages and decrease arc voltage. The thickness of ZrO2-Y2O3 coating is 16 μm thicker than that of ZrO2 coating and the maximum oxidation rate improves by 0.6 μm/min. In addition, the arc voltage decreases from 227 to 172 V. It can be seen that the rate of oxidation firstly increases to some extent and then decreases with the content of yttrium ion increasing. The growth rate reaches the maximum while the content of yttrium ion is 0.05 g·L−1. The maximum thickness is 90 μm.Compared to ZrO2 coating, the micropores of ZrO2-Y2O3 coating are less and the ceramic layer is repeatedly deposited by ZrO2 and Y2O3 ceramic particles. Meanwhile, the binding force between coating and substrate is better and the coating is uniform and compact. The ceramic layer is mainly composed of c-Y0.15Zr0.85O1.93□0.07, m-ZrO2, α-Al2O3, γ-Al2O3 and Y2O3. It is indicated that ZrO2 has been fully stabilized by yttrium ion through the formation of solid solution.

A top electrophoresis coating was deposited on the surface microarc oxidation (MAO) modified ceramic coating on AZ31 magnesium alloy. Microstructure and corrosion resistance of this composite coating were studied by SEM, electrochemical potentiodynamic polarization, and acid corrosion test. The results showed that the composite coating with a top electrophoresis coating on the surface of ceramic coating exhibited a better corrosion resistance compared with the coating formed by chemical conversion film combined with electrophoresis process. Corrosive ions could permeate into the substrate with corrosion time, and the composite coating was firstly destroyed around the scratch. The formation of composite coating with a higher adhesive force due to the porosity of the ceramic coating contributed to the improved corrosion resistance property.

Microstructure characterization, corrosion behavior, and electrochemical properties of magnesium anode materials containing 1–3 wt.% Sn in AZ61 alloy were studied by optical microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS), constant current method, potential polarization, and drainage. The results showed that amount of Mg2Sn phase increased, and recrystallization ratio of Sn-contained Mg alloys during rolling process was improved with increasing of Sn content. This resulted in uniform and refined grains. The results also demonstrated that discharge potential was improved and hydrogen release rate was reduced with the addition of Sn. As the current density increased, the release hydrogen rate was rising, owing to negative variance effect of magnesium alloys. The current efficiency gets to 87% at 20 mA/cm2. The main components of the corrosion products are easy-to-peel-off MgO and Al2O3 that can lead to more negative and stable work potential and accelerate battery reaction continuously.

In the present paper, the microstructures of three kinds of in-situ reinforcements Al-Ti-C, Al-Ti-B, and Al-Ti-B-C-Ce were deeply investigated using a combination of scanning electron microscopy, X-ray diffraction spectroscopy, and transmission electron microscopy. The effect of in-situ reinforcements on the room temperature and elevated temperature (350 &deg, C) tensile strengths of Al-13Si-4Cu-1Mg-2Ni alloy were analyzed. It is found that doping with trace amounts of B and Ce, the size of the Al3Ti phase in the in-situ reinforced alloy changed from 80 &micro, m (un-reinforced) to about 10 &micro, m, with the simultaneous formation of the AlTiCe phase. The Al-Ti-B-C-Ce reinforcement which is rapid solidified, was more effective and superior to enhance the tensile strengths of the Al-13Si-4Cu-1Mg-2Ni alloy, both at room and high temperatures than those of addition other reinforcements. The room temperature (RT) strength increased by 19.0%, and the 350 &deg, C-strength increased by 18.4%.