微型点焊时电极表面熔敷TiC涂层对电极失效的影响

研究了表面处理对微型点焊镀镍钢板和镍板时电极失效的影响.结果表明:微型点焊镀镍钢板和镍板时电极的失效主要是电极头部的塑性变形以及电极和镀镍板之间局部焊接的断裂发生在电极表面而导致的电极磨损;表面涂敷TiC的CuCrZr电极的寿命(1 200点)是CuCrZr电极寿命(600点)的两倍,表面处理能提高电极寿命的主要原因是表面涂敷的TiC颗粒能阻碍电极和镀镍板之间的局部焊接,以及减小电极表面的塑性变形.     

点焊镀锌钢板时电极表面熔敷TiC涂层对电极失效的影响

利用SEM、EDx和XRD等方法分析了在点焊镀锌钢板时电极表面熔敷TiC涂层对电极失效的影响.结果表明:点焊镀锌钢板时电极的失效机制主要是电极和镀锌板之间局部焊接的断裂发生在电极表面而导致的电极磨损,以及电极和镀锌板表面的锌之间的合金化.表面涂敷TiC的CuCrZr电极的寿命(1 200点)是CuCrZr电极寿命(500点)的2.4倍,表面处理能提高电极寿命的主要原因是在点焊镀锌钢板时表面涂敷的TiC层能阻碍电极和镀锌板之间的局部焊接和阻碍电极和镀锌板表面的锌之间的合金化.     

深冷处理对铜铬锆合金点焊电极寿命的影响

对深冷处理与原始未处理的CuCrZn电阻点焊电极进行寿命试验,利用超景深显微镜、光谱仪、XRD等分析测试手段比较深冷处理电极与原始未处理点焊电极寿命,观测点焊过程飞溅现象与焊点宏观形貌,研究失效电极表面塑性变形程度、表面合金层成分与物相,分析电极失效机理。结果表明,深冷处理电极相比原始未处理电极寿命大幅提升,使寿命从原来800点提高到3300点;深冷处理电极较原始未处理电极有较好的抗坑蚀能力,且其硬度提升,减缓电极端部塑性变形进程;深冷处理电极相比于原始未处理电极能够抑制电极表层Cu-Zn合金化进程,这是深冷处理电极寿命高于原始未处理电极的主要原因。     

镀锌钢板电阻点焊涂层电极与普通电极寿命分析

为增加镀锌钢板电阻点焊电极寿命,在普通铬锆铜电极表面沉积镍和金属陶瓷涂层后,研究涂层电极与无涂层普通电极的寿命.结果表明,相同条件下,涂层电极使用寿命大约是普通电极使用寿命的2.5倍;涂层电极抗塑性变形能力明显高于普通电极;普通电极端面有明显坑蚀、裂纹、合金层、自愈合层,而电极表面涂层能有效防止镀锌钢板电阻点焊过程中由...     

镀锌钢板电阻点焊涂层电极研究

文中采用焊点熔核直径标准测定了涂层电极的寿命并分析了点焊过程中电极端面的形貌及成分分布.试验结果表明,镀锌钢板电阻点焊时,在相同条件下,涂层电极抗塑性变形能力明显高于普通电极,涂层电极在焊接过程中所受到的损坏程度要比普通电极小;无涂层电极的使用寿命不少于800点,而涂层电极的使用寿命不少于2 200点,相比无涂层电极,涂层电极的使用寿命提高了2.5倍以上;电极表面的涂层能有效防止镀锌钢板电阻点焊过程中Zn在电极表面的粘连、剥离.     

热镀锌钢板连续点焊时电极损耗对焊接质量的影响

镀锌钢板电阻点焊时由于锌层的影响电极损耗非常严重。以厚0.8mm家电用热镀纯锌钢板DX51D+Z为研究对象,探究在正交试验优化焊接参数后,热镀锌钢连续点焊时焊接接头质量变化的规律和电极损耗的特点。结果表明,当采用I=11 kA、P=2 500 N、T=13 cyc的点焊工艺参数组合可获得力学性能最佳的点焊接头;连续点焊试验初期(150点前)焊点力学强度稳定且焊点成形较好,焊接后期(150～300点)接头力学强度波动大,焊接状况不稳定;电极损耗至失效是接头质量急剧下降的主要原因,电极失效形式为头部塑性变形、端面坑蚀和Cu-Zn合金化,在本试验条件下,Cr-Zr-Cu电极焊至150点后显现不稳定现象,电极寿命约280点;失效电极端面的Cu-Zn合金层约65μm。     

TiB_2-ZrB_2/Ni涂层电极点焊镀锌钢板失效过程分析

目的了解TiB_2-ZrB_2/Ni涂层电极点焊镀锌钢板时的失效机理。方法通过扫描电镜(SEM)、X射线衍射仪(XRD)、显微硬度测试等表征方法,研究TiB_2-ZrB_2/Ni涂层点焊电极点焊镀锌钢板时表面结构、物相及性能的变化。结果 TiB_2-ZrB_2/Ni涂层电极对提高点焊电极寿命有很大帮助,点焊电极寿命可提高5倍左右。涂层使点焊电极表面的硬度得以明显提高,减缓了点焊电极端部塑性变形的进程。ZrB_2-TiB_2/Ni涂层在一定程度上减缓了钢板镀层与点焊电极产生合金化反应的进程。结论 ZrB_2-TiB_2/Ni涂层电极由于具有一定的塑性,点焊过程中涂层不会出现完全脱落现象。涂层作用一直持续至电极失效,电极失效的形式主要表现为塑性变形。     

表面渗钛的镀锌钢板点焊电极寿命试验研究

对Cr-Zr-Cu合金的镀锌钢板点焊电极进行了表面渗钛处理，通过点焊电极寿命试验观测了表面渗钛处理前后镀锌钢板点焊的表面质量和电极端面状况。试验结果表明，采用表面渗钛可以提高镀锌钢板点焊电极的耐磨性和热稳定性，从而延长了电极的寿命。     

Al2O3弥散强化铜电极点焊镀铝钢板的行为研究

研究了含0．8％A12O3，的弥散强化铜电极材料在点焊镀铝钢板时的作用机理、失效形式及成因。结果表明，A12O3弥散强化铜电极在高温点焊条件下具有较高的强度、优良的传热性和抗蠕变性，其失效形式主要是塑性变形和表面合金化。电极上有少量粘附，但未发现再结晶。电极平均点焊寿命可达7200点，是一种较好的点焊电极材料。     

用电流波形控制法提高镀锌钢板点焊电极的寿命

作者通过分析镀锌钢板点焊电极寿命降低的原因，提出了提高镀锌钢板点焊电极寿命的电流波形控制法。采用该方法进行了点焊电极寿命试验，研究了工件表面飞溅率和电极寿命随焊前电流脉冲的幅值、焊前电流通电时间的变化规律。试验结果表明：采用电流滤形控制法可将镀锌钢板点焊电极的寿命由原来的400点以980点；工件表面的飞溅率及电极寿命与焊前电泳脉冲幅值、焊前电流通电时间有关。     

Effect of various kinds of severe plastic deformation on the structure and electromechanical properties of precipitation-strengthened CuCrZr alloy

The effect of various kinds of severe plastic deformation (equal-channel angular pressing and quasi-hydrostatic extrusion at 77 and 300 K) on the structural formation of precipitation-strengthened CuCrZr alloy has been studied. A combination of experimental methods has been used. Sputtering by deuterium ions was used as the tool for the layer-by-layer study of the alloy structure. The difference between the sputtering yields of the matrix (copper) and precipitates (Cr and Zr) allowed us to visualize the alloy structure to a total depth of 0.5?1 μm. The effect of severe plastic deformation on the precipitate distribution is considered. It has been shown that the main peculiarity of the microstructure is related to the high density of precipitates enriched in chromium, which completely determine the surface roughness. Their distribution is not related to the grain size. The combination of equal-channel angular pressing and quasi-hydrostatic extrusion was shown to lead to the increase in the microhardness of the CuCrZr alloy to 2300 MPa in the case of low-temperature quasi-hydrostatic extrusion (at 77 K) and to the retained high conductivity. It has been proved that the high anisotropy of precipitate shape, microhardness, and sputtering yield of the CuCrZr alloy is determined by equal-channel angular pressing.     

Electrode degradation mechanism during resistance spot welding of zinc coated steel using Cu-TiB2 electrodes

1 INTRODUCTIONResistance spot welding(RSW) is the mostcommonly used method for joining steel sheets inthe automotive industry . In RSW, a weld isformed between two workpieces through meltingand coalescence of a small volume of the material atthe faying surfaces due to the resistance heatcaused by the passage of electric current when theworkpieces are held together under a large elec-trode force[1 ,2]. Over the past decade ,the require-ment of i mproved corrosion resistance in automo-bil…     

点焊电极表面电火花沉积TiB_2涂层的特征

在CuCrZr电极表面通过电火花振动沉积制备了TiB_2功能涂层,测试了功能涂层的显微形貌、物相、硬度以及界面元素分布.试验表明,TiB_2涂层电极具有典型的电火花涂层结构,存在明显的元素互扩散,表明功能层与基体之间为冶金结合.但TiB_2涂层结构不致密,存在裂纹和孔洞,硬度较低.随着电火花电容和电压的增加.涂层的硬度降低.元素扩散和涂层氧化的加剧,是导致涂层硬度降低的主要原因.由于基体Cu的气化、脆性剥落和熔敷棒的切削作用,沉积TiB_2后基体质量反而降低.高电压下电火花沉积以及预涂敷Ni,都会导致基体质量降低更多.     

喷丸工艺对TC4钛合金梯度纳米晶结构的作用规律

目的通过改变喷丸的压力或时间,在钛合金表面制备出剧烈塑性变形(SPD)层较厚、硬度较高的梯度纳米晶结构。方法改变喷丸压力(0.3~0.6 MPa)或喷丸时间(15~60 min),调控TC4钛合金表面梯度纳米晶结构的变形层厚度和纳米晶晶粒尺寸。利用金相显微镜观察塑性变形层截面的组织形貌,通过X射线衍射仪(XRD)和透射电子显微镜(TEM)确定喷丸表面纳米晶的晶粒尺寸,通过显微硬度计对塑性变形层的截面硬度进行研究。结果一定喷丸压力(0.6MPa)下,SPD层和总变形层厚度分别在喷丸25、30 min时达到饱和值78μm和143μm。一定喷丸时间(25 min)下,SPD层和总变形层的厚度随喷丸压力的增加而增厚,在0.4 MPa时达到饱和,分别为78μm和120μm。当SPD层厚度进入饱和阶段后,表层晶粒大小和硬度强化程度都趋于稳定;在0.6 MPa下,当表面α相细化至稳定阶段时,晶粒尺寸为30~90 nm,表面硬度提高约30%。结论喷丸SPD层及总变形层的厚度随喷丸时间的延长或喷丸压力的增大而增厚,当SPD层厚度趋于饱和后,表面晶粒尺寸和硬度强化程度都已饱和。     

Surface tension of solids. Structure-mechanical approach

Problems of applying the classic and generalized Lippmann equations to adsorption studies on solid electrodes are shortly reviewed. Long-time thermodynamic discussion results in no clear-cut decision. A new nonthermodynamic approach is proposed considering the principal possibility and role of elastic and plastic deformations of the electrode surface during adsorption. The extremely thin electrode surface layers affected electrically and mechanically by adsorbate are supposed to be free of dislocations because of volume restriction. The nearest structure-mechanical analogs of such layers are the whisker crystals whose side surface could have one-and two-dimensional defects, but no active dislocations. Like whiskers, surface metal layers should possess a high ultimate strength close to the theoretical one and a purely elastic deformation. Special attention has been paid to the concepts of “reversible wholly plastic deformation (as in cleavage)” used for derivation of the generalized Lippmann equations for solids. This concept was shown to be an idealized one having no relation to the real plastic deformation of metals. It is a case of mixed notions since “cleavage” is not a kind of deformation. It is a kind of irreversible fracture mostly without the steps of plasticity. Affected only by adsorbate, the thin surface electrode layer should be considered as absolutely elastic body, whose plastic deformation is impossible, i.e. the Lippmann equation and other equations containing terms of plastic deformation cannot be used in thermodynamics of adsorption on the solid metals. The text was submitted by authors in English.     

7050铝合金表面亚微米化及其显微硬度的研究

通过改进7050铝合金表面纳米化技术(调节喷丸压力、弹丸直径和喷丸时间)在材料表面获得亚微米晶层,利用OM、XRD、SEM等方法对亚微米结构表层进行了观察和分析。结果表明:喷丸使7050铝合金表面发生一定的塑性变形,表层亚微米晶尺寸约88 nm,显微硬度比基体提高2倍。     

表面严重塑性变形过程中Ag-Cu共晶合金的结构演变

采用表面机械研磨处理技术对Ag-Cu共晶合金进行了表面严重塑性变形处理。采用硬度、透射电镜(TEM)等手段对Ag-Cu共晶合合金结构演变进行了研究。研究表明,采用表面严重塑性变形方法获得了具有纳米表层的Ag-Cu共晶梯度结构,合金变形层厚度为~100 mm,最表层纳米晶尺寸~10 nm。同时对其晶粒细化机制进行了讨论。     

Friction and wear behavior of electrodeposited amorphous Fe-Co-W alloy deposits

The microstructures, friction and wear behavior under dry sliding condition of electrodeposited amorphous Fe-Co-W alloy deposits heat treated at different temperatures were studied. A comparative study of hard chrome deposit under the same testing condition was also made. The experimental results show that the hardness and wear resistance of amorphous Fe-Co-W alloy deposits are improved with the increasing of heat treatment temperature, and reach the maximum value at 800℃, then decrease above 800℃. Under 40 N load, the wear resistance properties of the alloy deposits heat treated at 800℃ are superior to those of hard chrome deposit. The main wear mechanisms of amorphous Fe-Co-W alloy deposits heat treated below 600℃ are peeling, plastic and flowing deformation； when the deposits are heat treated above 700℃, they are plastic and flowing deformation. While the main wear mechanisms of hard chrome are abrasive wear, fatigue and peeling.     

Nanocrystallization process and mechanism in a nickel alloy subjected to surface severe plastic deformation

Bulk components made of a Ni-base C-2000 alloy with a face-centered cubic crystal structure and a very low stacking fault energy have been severely plastically deformed at the surface region to attain a grain size gradient ranging from nanocrystalline at the surface to coarse grained in the bulk. The evolution of microstructural characteristics has been studied as a function of the processing time employing a variety of analytical techniques, including extensive conventional and high-resolution transmission electron microscopy analyses. The thickness of the nanocrystalline surface layer is found to increase with the processing time. Deformation twinning is ubiquitous and occurs at the earliest stage of deformation and the deepest region of the material where plastic deformation has taken place in the surface severe plastic deformation process. A grain-refinement mechanism led by deformation twins and complemented by dislocation activity has been put forth to explain the nanocrystallization of the coarse-grained material employed in this investigation.