hardness

摘要： The effects of multipass friction stir processing(FSP)and Mg powder addition on the different microstructure parts,including the stir zone(SZ),heat-affected zone(HAZ),and thermomechanically affected zone(TMAZ)of Al 1050 alloy were investigated.Microstructural observations revealed that with the increase in the number of FSP passes,the grain size of the SZ decreased in the non-composite and composite samples,whereas that of the TMAZ and HAZ increased in the non-composite sample.Furthermore,the addition of Mg powder resulted in considerable grain refinement,and increasing the number of the FSP passes resulted in a more uniform distribution of Al-Mg intermetallic compounds in the in-situ composite sample.Results of the tensile test showed that the non-composite sample that underwent four passes of FSP exhibited a higher elongation percentage and a ductile fracture in comparison with those of the base metal and the composite sample.However,this sample exhibited a brittle fracture and a higher tensile strength in comparison with the base metal and the non-composite sample.The fabrication of composite samples resulted in a remarkable enhancement in hardness in comparison with the base metal and the non-composite samples that underwent FSP.

摘要： With its high strength and hardness, wear-resistant steel has become an important material in the field of construction machinery manufacturing.Given that quenching technology is a crucial component of wear-resistant steel production, the selection of the cooling method to be used during this process is important.In this study, the feasibility of quenching wear-resistant steel by air-atomized water spray cooling was studied, and the cooling rate, microstructure, and hardness of wear-resistant steel under various cooling device structures were analyzed.The results reveal that the air-atomized water spray cooling method is an effective technique in quenching wear-resistant steel.Furthermore, martensite and uniform hardness were obtained by the air-atomized water spray cooling technique.As the space between the nozzles in each row in the device increased, the cooling rate was reduced during quenching.Meanwhile, the martensite content decreased, and more carbides were observed in the martensitic structure.A mixture comprising self-tempered martensite and bainite was formed at a large distance over a longer period of time.All these factors resulted in lower hardness and worse property uniformity.

摘要： Nitrogen-doped diamond-like carbon(N-DLC)films were synthesized by helicon wave plasma chemical vapor deposition(HWP-CVD).The mechanism of the plasma influence on the N-DLC structure and properties was revealed by the diagnosis of plasma.The effects of nitrogen doping on the mechanical and hydrophobicity properties of DLC films were studied.The change in the ratio of precursor gas flow reduces the concentration of film-forming groups,resulting in a decrease of growth rate with increasing nitrogen flow rate.The morphology and structure of N-DLC films were characterized by scanning probe microscopy,Raman spectroscopy,and X-ray photoemission spectroscopy.The mechanical properties and wettability of N-DLC were analyzed by an ultra-micro hardness tester and JC2000DM system.The results show that the content ratio of N^(+)and N_(2)^(+)is positively correlated with the mechanical properties and wettability of N-DLC films.The enhancement hardness and elastic modulus of N-DLC are attributed to the increase in sp3 carbon–nitrogen bond content in the film,reaching 26.5 GPa and 160 GPa respectively.Water contact measurement shows that the increase in the nitrogen-bond structure in N-DLC gives the film excellent hydrophobic properties,and the optimal water contact angle reaches 111.2°.It is shown that HWP technology has unique advantages in the modulation of functional nanomaterials.

摘要： In this study, the characteristics of Graphite/Epoxy Composites (GECs) are evaluated from mechanical perspectives. Different weight percentages of graphite were used (0 - 7 wt%) for tensile and hardness experiments. Then the findings were discussed to ascertain the optimum mixing ratio of the graphite with the epoxy. The primary finding of this study is that the graphite weight fraction has a substantial impact on the composites’ mechanical performance. At a low percentage (1 wt%), the graphite has little influence on the tensile behaviour. An intermediate weight percentage of the graphite is considered optimum for mechanical performance in the epoxy composites as it slightly reduces the tensile properties and significantly improves the hardness. Micrographs of the fractured surface of specimens showed many signs that clearly explained why fractures had occurred. For instance, when graphite/epoxy composite contained a low proportion of graphite, the cleavage failure was very easy to observe because there was no sign of aggregation or the detachment of fillers.

摘要： TC17 titanium alloy which usually used on the fan and compressor disk were selected.Microstructure and mechanical property of joint were investigated.Microstructure character of different part of joint was analyzed also.Results showed that the joints included three zones,base metal(BM),thermal mechanical affected zone(TMAZ)and weld zone(WZ).The microstructure of joint middle part was equiaxial grains,but the bottom part was the elongated grains.Dynamic recrystallation happened at the weld zone.Tensile test result showed that joint tensile strength equal to that of the TC17 base metal.The average hardness value of the HAZ was 486 HV which was higher than that in the BM and WZ.

摘要： The rapid industrial development calls for alloys that possess higher comprehensive properties. In this study, the effect of microalloying La addition on the precipitation behavior during artificial aging as well as the mechanical properties and electrical conductivity of Al-Mg-Si alloys were investigated by thermal analysis, microstructural characterizations and properties tests.The results demonstrated that micro-alloying La addition does not change the whole precipitation sequence during the artificial aging of Al-Mg-Si alloys as well as the atomic structure of the precipitates. However, the higher La-vacancy binding energy as well as the strong La-Si and La-Mg interactions can decrease the solubility of Si and Mg in the Al matrix and the β″ precipitation activation energy from 89.9 to 76.7 kJ/mol, leading to the improvement of the strength and electrical conductivity of Al-Mg-Si alloys simultaneously. The microstructural features affecting the strength and electrical conductivity were theoretically discussed in terms of the La addition.

摘要： In the present work, titanium alloy with a composition of Ti-6.5Al-3Mo-1.9Nb-2.2Sn-2.2Zr-1.5Cr (TC21) was subjected to plastic deformation and aging processes. A Plastic deformation at room temperature with 2%, 3% and 4% stroke strain was applied on the studied samples. Then, the samples aged at 575°C for 4 hr. By applying different plastic deformation ratios, the structure revealed an elongated and thin β-phase embedded in an α-phase. Secondary α-platelets were precipitated in the residual β-phase. Maximum hardness (HV440) was obtained for 4% deformed + aged samples. Minimum hardness (HV320) was recorded for the as-cast samples without deformation. The highest ultimate tensile strength of 1311 MPa was obtained for 4% deformed + aged samples due to presence of high amount of dislocation density as well as precipitation of secondary α-platelets in the residual β-phase. The lowest ultimate tensile strength of 1020 MPa was reported for as-cast samples. Maximum elongation of 14% was registered for 4% deformed + aged samples and minimum one of 3% was obtained for as-cast samples. Hence, strain hardening + aging can enhance considerably the elongation of TC21 Ti-alloy up to 366% and 133% in case of applying 4% deformation + aged compared to as-cast and aged samples without applying plastic deformation, respectively.

摘要： The objective of this study was to evaluate the effect of heat treatment on decorative properties including glossiness,color coordinates including lightness(L),blue-yellow(b^(*))and red-green(a^(*)),hardness(shore-D)morphological characterization and thermal properties of some exotic wood species.Heat treatment of anigre(Aningeria altissima),cedrorana(Cedrelinga catenaeformis),cemara(Casuarina sumatrana)and coronilla(Scutia buxifolia)wood materials were performed in an oven with a programmable controller at 210°C for 3 h.The obtained samples were conditioned in a climate cabin and the decorative properties,morphological characterization with scanning electron microscopy(SEM)and thermal properties with thermogravimetric analyzer(TGA)of the obtained samples were determined.The test results showed that color got darker with heat treatment,specifically L and b^(*)decreased,and a^(*)increased for anigre and cedrorana but a^(*)decreased for cemara and coronilla.The glossiness for all samples generally increased from 20°to 85°but heat treatment decreased the glossiness.The density generally decreased with heat treatment and decrease ratio in the density was found to be in range from 5.6%to 10.6%.According to the SEM analysis,some cracks,pit aspiration and layer decomposition in the micro level of the wood structure were detected.TGA showed that heat treatment makes thermally more stable wood.As a result,it can be said that heat treatment improved the decorative properties of the exotic wood.

摘要： From the mechanistic point of view,magnesium alloys are lightweight materials and are receiving increasing attention in the past several years in various fields.Prof.Liang Zhen from Harbin Institute of Technology,China and the United State military are showing keen interest in the development of magnesium alloys as ballistic resistant material.However,their use is still limited owing to low ductility,low formability,and average mechanical properties.The magnesium alloys components must withstand the shockwave under hypervelocity ballistic impact.The ballistic testing can produce gradient variations of the strain and stress-energy away from the crater,and useful for the development of these alloys in the military and aerospace industry.Therefore,the present review article shed light on the post deformation analysis of the Mg alloys subjected to the different projectiles under ballistic impact,and the underlying mechanisms were discussed.In the end,some important issues regarding the ballistic impact and further studies in this field were proposed.

摘要： fields such as lightning strike susceptibility,electromagnetic energy from radar,airborne radio frequency transmitter.To provide high-intensity radiated field protection(HIRFP)for the electric and electronic aircraft system and defied the EMI effect on it,metal matrix composite was conquered.To provide the dynamic everincreasing requirement of industries,it is necessary that Al6061 metal matrix composite assisted with AL2O3 and fly ash is used to construct the aircraft to provide HIRFP.The thickness of the material can be maintained as low as possible to use it as a coating material for the aircraft surface.X-band for oblique incidence is used to measure electromagnetic and mechanical safeguarding properties of composites.Design/methodology/approach-Day by day,the applications of aerospace are becoming digital and automated.Proper shielding techniques are required to operate digital electronic devices without electromagnetic interference.It leads to a rapid rise in temperature,thermal ablation,delamination,and adverse effects on the electric and electronic aircraft system.Fly ash,a metal matrix material composite AL6061 with different percentages of reinforcement of Al_(2)O_(3),was contemplated and experimented with for mechanical properties like tensile strength,density and hardness.Findings-The obtained results compared with adjusted values and an improvement of 0.19,0.18,0.14 g/cm3 for density of MMC-1,MMC-2,MMC-3.31,11 MPa for tensile strength of MMC-1,MMC-2.24,27,23 BHN for hardness of MMC-1,MMC-2,MMC-3.With regard to the shielding effectiveness the results compared with adjusted values and obtained 11.36,14.56,19.47 dB better value than it.According to the above results,fabricated MMC’s provide superior results for a defined application like HIRFP(Surface material of aircraft).Practical implications-It can be used to protect electronic devices under a high-intensity radiated field,mainly in aircraft design to protect from lightning effect.Originality/value-For a better approximation of the signal toward the practical case,the oblique incidence was considered with a different combination of Al_(2)O_(3)and fly ash,reinforced to pure AL6061 to get better shielding and mechanical properties.