Ti6Al4V合金超声深滚层的组织结构特征

采用超声深滚技术对Ti6Al4V合金进行表面机械强化处理,使用扫描电镜、硬度分析、X射线衍射和透射电镜等分析手段研究超声深滚处理Ti6Al4V合金表面层的组织结构特征。结果表明:超声深滚处理后,材料表层组织严重细化,形成了纳米结构层,表面晶粒尺寸小于20nm。晶粒细化层的深度约为0.15mm,在0.15mm深度处,虽然晶界结构保持完整但晶粒内部位错密度增加。分析了组织结构细化对于改善疲劳性能的意义。

Research on Properties of Carbon Fiber/Epoxy Resin Composite Material by Microwave Curing

Microwave irradiation was used to reduce the curing time of carbon fiber/epoxy resin composite material.The properties of carbon fiber/epoxy resin composite material under microwave curing were investigated by thermogravimetry(TG),dynamic mechanical analysis(DMA),impact strength test and scanning electron microscope(SEM).The results show that composite materials patch have high thermal stability after microwave curing.The initial degradation temperature is 330.9℃,the maximum thermal decomposition rate is at 368.1℃.When the layer of composite materials patchis 4 layers,the dynamic mechanical properties are the best after microwave curing.The initial storage modulus is 43.2 GPa,increased 28.3 GPa and 27.1 GPa than 3 layers and 5 layers,the glass transition temperature(Tg)is 67.48℃,increased about 12 ℃than 3 layers and 5 layers.Microwave curing can significantly improve the infiltration capacity of epoxy resin,enhance interfacial bonding,and increase the impact strength of composite patch.Under microwave curing,the impact strength of 3,4,5-layers composite material patches increases 35.9%,6.4% and 15.1%,respectively than heating curing.The SEM analysis of impact fracture surface shows that microwave curing can improve the interface of carbon fiber and epoxy resin.

Preparation of Al-based Amorphous/Nanocrystalline Composite Coating on Mg-based Alloys Precipitated by Arc Spraying Process

The Al-based amorphous and nanocrystalline composite coatings with the composition of Al-Ni-Y-Co and Al-Ni-Mm-Fe were prepared on AZ91 Mg-based alloys by high velocity arc spraying technique(HVAS).The structure character of the coatings indicates that coatings contain the mixture of amorphous phases and crystalline and there are both less than 2%porosity.The electrochemical tests of the coatings and the substrate were studied.The coatings show the passivation ability during polarization,but AZ91 Mg-based alloys show little passivation.The corrosion current density of the coatings is lower than that of AZ91 Mg-based alloys.The results show that the coatings have an excellent corrosion resistance for AZ91 Mg-based alloys in 5 wt%NaCl solution.

Advanced Surface Engineering Technologies for Remanufacturing Forming

Based on the foreign remanufacturing mode,which relies mainly on Part-Replacing Repair Method and Size-Changing Repair Method,China has explored and practiced the new remanufacturing mode,which relies mainly on Surface Repair and Performance Improving Method.The aim of remanufacturing forming is to renew rapidly the original size of the waste components rapidly,and then improve their service performance.The advanced surface engineering technology,especially the high density heat source surface forming technology,is the important technique to carry out rapid forming.Based on the arc heat source,plasma heat source and laser heat source,three kinds of high density heat source remanufacturing forming technologies,such as high speed arc spraying forming technology,micro-arc plasma forming technology,and laser cladding forming technology,have been developed.The benefits of remanufacturing forming based on advanced surface engineering technologies are great.

Remanufacturing Shaping System Based on Pulsed Plasma Arc Welding

Based on the pulsed plasma arc welding(PPAW),a rapid remanufacturing shaping system,including a structured light scanning reverse engineering(RE)system,a robot system and a PPAW source system have been developed.The new rapid remanufacturing shaping system can rapidly and accurately repair the worn parts with different damaged degrees and thus extend their life cycle.In the present paper,the whole process of repairing worn parts is described.Firstly,the scanning model of a worn part is obtained by using RE system based on reconstructing approach.Compared with standard CAD model in the undamaged setting,the surface profile and the extent of damage area are obtained.Secondly,the weld repair path is designed by slicing the point cloud model of damage area.This path consists of multilayer parallel lines that produce parallel overlapped weld beads which cover the damaged area.By off-line programming techniques,the robot executable program as document format is transmitted to the robot controller for repairing worn parts.Finally,the weld repair experiments on worn steel plane plate and damaged column are performed to evaluate the remanufacturing system.

Research of Electrochemical Noise Technology on Corrosion Resistance

This paper is focus on the corrosion resistance property analysis on three electric blasting of the coating-FeAl,FeCrAl,FeCrAlRE by electrochemical noise technology,acceleration of copper acetate salt spray accelerated corrosion test.According to a comparative analysis of three tests coated by the Impedance curve,FeCrAlRE coating power spectral density(SPD)curve and Power curve,FeAl,FeCrAlRE coating has two more notable for the corrosion resistance properties than FeAl,FeCrAl coatings.

Progress of Nondestructive Detection Technology on Remanufacturing Coatings

The defects of remanufacturing coatings,such as micro-cracks,micro-pores,oxide inclusion,and fatigue cracks producing in the service process have great influence on the qualities and lives of remanufacturing coatings.This paper summarizes several methods used for detecting coating defects,including ray method,ultrasonic method,eddy method,magnetic memory method,acoustic emission method.The advantages and limitations of the above methods are also discussed.The detection results by ray method are visualized,and it is easy to achieve qualitative,quantitative and locating detection,but this method has incipient fault and low detecting sensitivity.Ultrasonic detection can exactly locate defects,and it is sensitive to plane defects,but the detection has dead zones,and it is inconvenient to perform qualitative and quantitative measurement.Eddy method detects fast,but it only can detect conductive materials,and is difficult to achieve qualitative,quantitative and locating detection.Magnetic memory method is sensitive to ferromagnetic materials,but it can not detect nonferromagnetic materials and is difficult to attain quantitative measurement.Acoustic emission method has an extensive detection range and high sensitivity,but it has big noise interference,and is hard to achieve qualitative detection.In conclusion,it describes the application prospect of each method for detecting coating.

Research on Tribological Characteristics and Worn Surface Self-Repairing Performance of Nano Attapulgite Powders Used in Lubricant Oil as Addictive

As a kind of natural nanometer materials,the attapulgite has been widely used in industry,agriculture,environment,food substance,medicament and many other fields.Few researches about attapulgite used in lubricant oil as additive were made,and those were only at a preliminary stage of exploration.The tribological characteristics of attapulgite powders with the different contents added to CD 15W/40 lubricant oil were researched through"plane-on-plane"configuration friction and wear tester,and the self-repairing performance of 45#steel worn surface was examined via ring-on-block configuration test.XRD,SEM,EDS,TEM were employed to analyze the surface morphologies and elementary composition of the samples'worn surface.Furthermore,wear self-repairing mechanism of attapulgite additive to lubricant oil was explored.The results showed that:the optimal content of attapulgite powders in oil CD 15W/40 was 0.5 wt%,and the stable friction coefficient can be reduced to 0.02,then the friction reduction performance can be enhanced by 82.5%;Smooth worn surface were formed of the chemical reaction film containing elements O,Si,Fe;Friction reduction and self-repairing mechanism had a relation with the crystal structure of attapulgite.

Fretting Corrosion Behavior of Zn-Al-Mg-RE Coating under Dry Friction and NaCl Solution

The fretting behavior of Zn-Al-Mg-RE coating prepared by high velocity arc spraying was studied for the first time in this paper.All specimens were fretted in air and 3.5%NaCl solution independently.The worn surfaces of the coating were investigated by scanning electron microscopy and X-ray energy dispersive spectroscopy.Fretting tests have shown that friction coefficient in 3.5%NaCl solution was similar to dry condition for Zn-Al-Mg-RE coating.Study of worn surfaces revealed the main mechanism in dry friction was the oxidative wear;while in 3.5%NaCl solution,the main mechanisms were delamination process and abrasive wear.

Metallurgy Failure Analysis for an Early Fracture Engine Intake Valve Made of 85Cr18Mo2V

By means of analysis technique such as scanning electron microscopy(SEM)equipped with energy dispersive spectroscopy(EDS),and transmission electron microscopy(TEM),deep metallurgy failure analysis for an early fracture engine intake valve made of the martensite material of 85Cr18Mo2V was performed through macroscopical and microcosmic as well as chemical composition angles.According to the result of SEM,this valve belonged to fatigue fracture.The crack sources of dense micro-holes near the surface of intake valve and SiO2 impurity are the direct reasons to cause the valve failure.The EDS analysis for the fatigue source region approved that superfluous Si,O and Al impurity existed.The TEM observation of the slice cut from the region closing to the fracture surface showed that deep areas near the surface of valve were oxidized severely.The material structure got brittle due to the generation of Fe3O4.Cracks will be produced in these oxidation areas under high cycle fatigue loading.Consequently,the synthetical action of various factors finally caused the fracture of valve.

High Velocity Arc Spraying for Automotive Industry

A diesel engine crankshaft is failed in journal and the dominant failure mechanism is wear.A 6R robot-based automatic high velocity arc spraying system was developed in this study.The remanufacturing process of engine crankshaft was designed based on the newly developed automatic spraying system and the FeAlNbB cored wire.The two spraying way planning were designed.The results of industrial application in miniature show that,both of the main shaft journal and the crank journal of the crankshaft can be deposited of coating in only one procedure using the developed automatic spraying technology,and a reliable quality remanufactured part was obtained.A comparative evaluation shows that the improvement process offers several benefits.Such as,the coating bond strength and spray rates are all highly increased;the remanufactured cost and time are decreased.Furthermore,this technology has several advantages such as energy and material saving,and environmental protecting,a wide application foreground for this technology is therefore performed.

Influence of AAO Treatment Parameters on Characterizations of Surface Pores on 316L Stainless Steel

Recently a new kind stent,porous drug-eluting stent,has been developed to overcome the problems of bare metal stent(BMS)and drug-eluting stent(DES),and the clinic results reveal that it combined the advantage of BMS and DES.In this paper,a new method to fabricate surface pores on 316L stainless steel stent using anodic oxidation of aluminum mask film deposited by magnetron sputtering on 316L substrate was reported.The effect of experimental parameters,such as anodization time,anodization voltage,anodization solution and anodization temperature,on the pores'size distribution and density are investigated using SEM.It is found that the pores characterizations strongly depend on anodization time and pores expanding rate through AAO films and on stainless steel surface.