Effects of electric pulse on microstructure of Al-Si alloy in liquid and solid states

In order to investigate the change in liquid microstructure of Al-Si alloytreated by electric pulse (EP), X-ray diffraction tests with liquid Al-Si alloy and ZL109 alloytreated or not by EP were carried out. The results show that the number of Al-Si atomic clustersdecreases and that of Al-Al and Si-Si atomic clusters increases for the treated samples. The testswith ZL109 alloy indicate that a large amount of primary crystal Si appears in the solidifiedmicrostructure after treated by EP. It is found that EP can change the microstructure of liquidmetal by affecting the probability of electrons appearing in different atoms (Al and Si) in theliquid metal. The combining force of different atoms decreases relatively, and that of the sameatoms increases, which is the main reason of reducing the atomic cluster with different atoms(Al-Si) and increasing the atomic cluster with the same atoms (Al-Al, Si-Si). The increasing of theatomic cluster with the same atom cluster resulted in the increasing of Si activity and the higherpoint of eutectics in the phase diagram. It makes a lot of primary silicon appeared in ZL109 alloy.

Microstructure and corrosion resistance of a Mg2Sn-dispersed Mg alloy subjected to pulsed electron beam treatment

We report that the corrosion resistance of a Mg-Sn-based alloy with MgzSn precipitates can be considerably improved by surface modification using pulsed electron beam treatment.The alloy subjected to a pulse electron beam treatment showed a modified surface layer with a thickness of〜12 μm,appearing more resistant to corrosion attack than the bare surface of the alloy.In 0.6 M NaCl solution,the alloys with and without the surface modification exhibited average corrosion rates of 4.3 and 8.1 mm y^-1,respectively.The improved corrosion resistance was attributed to reduced cathodic activation,resulting from the surficial reduction of relatively noble Mg2Sn precipitates.

Microstructural characterization of Inconel 718 alloy after pulsed laser surface treatment at different powers

An annealed Inconel 718 alloy was surface-treated by pulsed laser at three different powers（100, 50 and 25 W）. Microstructural changes induced by the laser treatments were characterized by use of electron backscatter diffraction and electron channeling contrast imaging techniques. Results show that both annealing twins and strengthening precipitates profusely existing in the as-received specimen are dissolved at elevated temperatures during the laser irradiation. Meanwhile, in the melting zone（MZ）, densities of low angle boundaries（LABs） are greatly increased with a large number of Laves phases preferentially distributed along such LABs. For different specimens, widths and depths of their MZs are found to be gradually reduced with decreasing the laser powers. Orientation analyses reveal that the columnar grains in the MZ of the 100 W specimen could inherit orientations existing in the matrix while lower laser powers promote the formation of more nuclei with scattered orientations to grow to be granular grains in the MZ. Hardness tests reveal that the MZs of all laser-treated specimens are softer than the matrix probably due to both precipitate dissolution and grain coarsening.

Pulse Electromagnetic Effect on Metal Melts

The aim of the work was the study of the effect of NEMP （nanosecond electromagnetic pulses） on steel properties. Steel treatment was performed under the workshop conditions. The mechanical properties and the microstructure of the experimental samples and samples prepared by usual way were analyzed. The treatment of metal melt with nanosecond electromagnetic pulses at the crystallization stage makes it possible to change mechanical properties of metal and its structure.

Effectiveness of pulsed radiofrequency on the medial cervical branches for cervical facet joint pain

BACKGROUND Cervical facet joint pain(CFP)is one of the most common causes of neck pain and headache.Persistent CFP deteriorates the quality of life of patients and reduces their productivity at work.AIM To investigate the effectiveness of pulsed radiofrequency(PRF)stimulation of cervical medial branches in patients with chronic CFP.METHODS We retrospectively included 21 consecutive patients(age=50.9±15.3 years,range 26-79 years;male:female=8:13;pain duration=7.7±5.0 mo)with chronic CFP,defined as≥4 on the numeric rating scale(NRS).We performed PRF stimulation on the cervical medial branches.The outcomes of the PRF procedure were evaluated by comparing the NRS scores for CFP before treatment and 1 and 3 mo after treatment.Successful pain relief was defined as a≥50%reduction in the NRS score at 3 mo when compared with the pretreatment NRS score.RESULTS No patient had immediate or late adverse effects following PRF.The average NRS score for CFP decreased from 5.3±1.1 at pre-treatment to 2.4±0.6 at the 1 mo follow-up,and 3.1±1.1 at the 3 mo follow-up.Compared to the NRS scores before PRF stimulation,those at 1 and 3 mo after PRF stimulation had significantly decreased.Eleven of the 21 patients(52.4%)reported successful pain relief 3 mo after the PRF procedure.PRF stimulation on cervical medial branches may be a useful therapeutic option to control chronic CFP.CONCLUSION PRF stimulation of the cervical medial branches may be used as an alternative treatment method in patients with CFP.PRF can effectively alleviate CFP,and is safe to perform.

Nanosecond Pulse Treatment on Water and Water Solutions

The experiment results of the nanosecond electromagnetic pulses action on water and water solutions containing radionuclides are described. An activity decrease of radionuclides solution is observed in many experiments. The results may be useful to create water purification devices from heavy metals and radionuclides.

Interface strengthening for thermal sprayed WC-10Co4Cr coating subjected to pulsed magnetic treatment

The reliability of the coated industry components demands ideal fatigue properties of the coating,and it is mainly determined by the performance of the interfaces.In this study,pulsed magnetic treatment(PMT)was applied to the thermal sprayed WC-10Co4Cr coating,and the fatigue lifetime of the coated bolt increased by 219.82%under an imitation of the operating mode condition.Scratch tests further proved that both the adhesion and cohesion strength were improved after PMT,and they benefit from the interface strengthening effects.The formation of coherent WC/Co interfaces was characterized by in-situ transmission electron microscopy(TEM),and the molecular dynamic simulations indicate that the work of separation of these interfaces is much higher than the original disordered ones.Residual stress was relaxed and distributed more homogeneously after PMT,and it mainly contributes to the coating/substrate strengthening.This work provides a new post-treatment method focusing on the interfaces in the WC-based coating and gives insight into its mechanism so that it is hopeful to be applied to other kinds of coatings.

Mechanism and application of mechanical property improvements in engineering materials by pulsed magnetic treatment:A review

Pulsed magnetic treatment(PMT)has been adopted as an effective strengthening method for engineering materials and components in recent years,and the development of its application depends on the comprehensive understanding of the nature of PMT.The deep mechanism was thought initially to be the magnetostrictive effect,while further investigation found that the magnetic field could lead to the change of the defect states in the crystal,which is called the magnetoplastic effect.Due to the complexity of the engineering materials,manifestations of the magnetoplastic effect become more diverse,and they were reviewed in the form of microstructure homogenization and interfacial stabilization.Further,the mechanism of the magnetoplastic effect was discussed,focusing on the changes in the spin states under the external magnetic field.Microstructure modifications could also alter material performances,especially the residual stress,plasticity,and fatigue properties.Therefore,PMT with specific parameters can be utilized to obtain an ideal combination of microstructure,residual stress,and mechanical properties for better service performance of different mechanical parts,and its applications on machining tools and bearings are perfect examples.This work reviews the effect of PMT on the microstructure and properties of different materials and the mechanism,and it also summarizes the fundamental applications of PMT on essential mechanical parts.

Combination of eddy current and heat treatment for crack healing and mechanical-property improvement in magnesium alloy tube

The continuous eddy current pulse treatment(ECPT)combined with heat treatment was employed to heal the microcracks in spin formed Mg alloy tubes and improve their mechanical properties in this study.The results show that all the microcracks in different tube specimens were almost healed after different continuous ECPT schemes up to 15 cycles.The schemes with less cooling intervals exhibited better healing effect and increased the strength and elongation of Mg alloy tubes more obviously.After aging treatment,the strength improvement of the specimens with ECPT was more remarkable than that of the specimens without ECPT,and the elongation decrease of the specimens with ECPT was less evident than that of specimens without ECPT due to the segregation of RE elements on the crack surface.Besides,after solution treatment,the strength reduction and ductility improvement of the specimens with ECPT were more pronounced than that of the specimens without ECPT owing to the notable decrease of dislocation density of the specimens with ECPT.Both narrowed cracks induced by ECPT and the segregation of precipitates in the vicinity of microcrack surface during aging treatment contributed to the maximum strength in the as-spun specimens with ECPT followed by aging treatment.

Pulsation Treatment on the Modification of Crystal with Cold Simulation

Since the separation of crystal of KCl saturated aqueous is similar to the crystallization of liquid metals, the melts nucleation can be simulated by the experiment of the crystal of salt aqueous solution. In this experiment pulsation treatment was imposed on KCl saturated aqueous in order to study the effect of pulsation treatment on crystallization in the salt solution, and the influence of different pulsation treating time, super-heating and bine of prescription were investigated. The results show that it is possible to modify the crystallization over satured solution temperature and the degree of under-cooling for salt crystal separation was reduced by applying pulse treating on KCl saturated aqueous solution. In addition, this technology may generate embryos for nucleation even at the temperature over melting point or satured solubility.

Non-Invasive Treatment to Grade 1 Essential Hypertension by Percutaneous Laser and Electric Pulse to Acupoint with Music:A Randomized Controlled Trial

Objective： To study a non-drug therapy for hypertension disease by combining percutaneous laser and electric pulse stimulation to acupoint with music, and to test the efficiency of the combining treatment to grade 1 essential hypertension. Methods： A total of 174 patients with grade 1 essential hypertension were randomly assigned to 3 groups with a random number table after Chinese medicine（CM） syndrome differentiation： the photoelectric and musical treatment group（Group 1, with a self-developed multi-mode audio frequency pulse photoelectric therapeutic apparatus）, acupuncture group（Group 2）, and oral placebo group（Group 3）, 58 cases per group. The curative effect of each group was evaluated by the changes of blood pressure and CM syndrome integral before and after treatment. Results： Compared with Group 3, there were significant decrease of blood pressure and CM syndrome integral in Group 1 and Group 2（P〈0.01）. Compared with Group 2, Group 1 showed the highest decrease in systolic pressure（P〈0.017）. The total effective rate of anti-hypertension in Group 1（91.38%, 53/58） was significantly higher than that in Group 2（74.13%, 43/58） and Group 3（18.97%, 11/58, P〈0.05 or P〈0.01）; and that in Group 2 was also significantly higher than that in Group 3（P〈0.01）. There were significant difference in the total effective rate of CM syndrome integral in both Group 1（93.10%, 54/58） and Group 2（84.48%, 49/58） as compared with Group 3（17.24%, 10/58, P〈0.01）, while there was no significant difference between Group 1 and Group 2（P〉0.05）. Conclusions： The multi-mode audio frequency pulse photoelectric therapeutic apparatus, combining music, laser and electric pulse stimulation, is clinically useful for grade 1 essential hypertension. This ＂three in one＂ therapy method is non-invasive, easy and simple to handle. It is expected to be popularized as a new alternative treatment.

Effect of grain refinement on cutting force of difficult-to-cut metals in ultra-precision machining

The nickel-based superalloy Inconel 718 is treated with Coupled Ultrasonic and Electric Pulse Treatment(CUEPT),and the surface grain is refined from the average size of 9550.0 nm to287.9,216.3,150.5,126.3,25.8 nm by different effective treatment currents,respectively.The ultraprecision turning experiments are carried out on the processed workpiece after CUEPT.The experimental results show that the average cutting force increases with the decrease of surface grain size.Moreover,a mathematical model that can describe the relationship between grain size and cutting force is established,and the calculated results match the experimental results well.The calculated results also indicate that the variation of cutting force caused by the same variation of grain size decreases as the degree of grain refinement increases.Finally,the influence mechanism of grain refinement on cutting force is analyzed.The improvement of stability of grain boundaries and the increase of number of grain boundaries cause the increase of cutting force after grain refinement.