Tool wear mechanism in turning of novel wear-resisting aluminum bronze

1　ＩＮＴＲＯＤＵＣＴＩＯＮＡｌｕｍｉｎｕｍｂｒｏｎｚｅｉｓａｎｉｍｐｏｒｔａｎｔｅｎｇｉｎｅｅｒｉｎｇｍａｔｅｒｉ ａｌｄｕｅｔｏｉｔｓｅｘｃｅｌｌｅｎｔｐｈｙｓｉｃａｌ ,ｍｅｃｈａｎｉｃａｌ,ａｎｔｉ ｃｏｒｒｏ ｓｉｏｎａｎｄｗｅａｒｒｅｓｉｓｔｉｎｇｐｒｏｐｅｒｔｉｅｓ .Ｏｕｒｒｅｓｅａｒｃｈｇｒｏｕｐｄｅ ｖｅｌｏｐｅｄａｓｐｅｃｉａｌｔｙｐｅｏｆｈｉｇｈｓｔｒｅｎｇｔｈ ,ｗｅａｒ ｒｅｓｉｓｔｉｎｇａ ｌｕｍｉｎｕｍｂｒｏｎｚｅ(ＫＫ ) ,ｗｈｉｃｈｉｓｅｘｃｅｐｔｉｏｎａｌｌｙｇｏｏｄｆｏｒ…     

钨铜/铍青铜异质钎焊界面组织与性能

采用BAg56CuZnSn,BAg50ZnCdCuNi和BAg49ZnCuMnNi银钎料实施了钨铜合金/铍青铜异质材料接头的感应钎焊连接,研究了其钎焊界面组织与力学性能.结果表明,3种银钎料均能获得完好界面钎焊接头,钎料与钨铜和铍青铜形成较好冶金结合.钎料与铍青铜界面冶金结合充分,形成明显互扩散区.钎料与钨铜钎焊界面清晰,且钎料向钨铜近界面区域形成明显扩散渗入现象.强度测试表明,BAg49ZnCuMnNi钎焊接头强度最高,达到250 MPa,接头断裂均发生在钨铜侧钎焊界面.分析表明,钎料向钨铜渗入明显促进界面结合,钎料中添加镍,由于镍与钨的扩散互溶进一步提高界面冶金结合,Mn元素添加明显细化钎缝晶粒,接头强度显著提升.     

碳化硅颗粒增强铝基复合材料的界面特征及力学性能

研究了氧化态和原始态碳化硅颗粒增强铝基复合材料的界面结构及其对复合材料弯曲强度的影啊。结果发现．氧化处理后碳化硅与基体铝界面上有一ＳｉＯ２非晶层，该非晶层内由于铝的扩散作用而形成铝的浓度梯度。原始态碳化硅与铝的界面上则无此非晶层．由于此非晶层的作用．导致界面结合强度的提高从而增加了复合材料的弯曲强度。     

PCD刀具高速干式切削铜合金的磨损研究

使用PCD刀具对锡青铜合金材料进行高速干式切削试验,分别采用扫描电镜（SEM）、X射线能谱仪（EDS）对刀具的磨损形貌进行观察和磨损区域化学成分进行分析,并以此研究了PCD刀具的磨损机理。结果表明:在高速干式切削条件下,PCD刀具主要表现为前刀面的片状剥落和后刀面的轻微破损;同时还伴随着机械应力和热应力冲击下的脆性破损,出现崩刃、切削刃整体断裂以及前后刀面的大面积剥落。刀具磨损的主要原因是高温作用下的氧化磨损和扩散磨损。      

电场对AZ31B与Al连接界面扩散反应和扩散溶解层结构的影响

应用电场激活扩散连接技术(FADB)实现AZ31B与Al的连接。研究了电场对AZ31B/Al结合界面扩散反应和扩散溶解层结构的影响。采用光学显微镜、扫描电子显微镜、X射线能谱与X射线衍射仪等方法分析了扩散溶解层的显微组织、相组成和元素分布。结果表明,在FADB条件下以铝粉为中间层时扩散溶解层由均匀共晶层、过渡层和胞状晶组成;以铝箔为中间层时由镁合金侧共晶层和铝侧过渡层构成。电场强度对扩散溶解层宽度和形态均有显著影响。溶解层随电流密度升高而变宽。以铝粉为中间层在温度450℃,时间50min,电流密度80A·cm-2时过渡层宽度为120μm,为未施加电场时的12倍。电流对共晶层内晶粒尺寸有显著影响。当电流密度由28A·cm-2升至48A·cm-2时,点状晶粒晶粒尺寸由2μm降至0.5μm。     

铜/铝磁脉冲半固态辅助钎焊界面扩散过程

结合分子动力学模拟和试验研究,对铜/铝管磁脉冲半固态辅助钎焊界面原子扩散过程进行了研究.结果表明,在铝侧扩散界面原子主要在界面的无序原子层中相互扩散,且各元素的扩散行为不均匀,铝基体原子向钎料的扩散速度远小于钎料原子向铝基体扩散的速度;铜侧界面在模拟设置的冲击速度下,扩散层很薄且厚度变化并不明显.测量不同冲击速度下铝侧界面的扩散层厚度发现,随着冲击速度增加,模拟的扩散层厚度呈线性增加,与试验结果相符.根据模拟与试验结果建立了在相同或相近的冲击速度下,模拟界面扩散层厚度与试验界面扩散层厚度之间的关系,模拟结果能够较好地预测试验界面扩散层厚度,最大误差为2.8%.     

Hard AlTiN, AlCrN PVD coatings for machining of austenitic stainless steel

The austenitic stainless steels in general are considered to be difficult to machine materials. This is mainly due to the high plasticity and tendency to work-harden of the austenitic stainless steel, which usually results in severe cutting conditions. Additionally, austenitic stainless steels have much lower thermal conductivity as compared to structural carbon steels; this inflicts high thermal impact within the chip-tool contact zone, which significantly increase the cutting tool wear rate. The machineability of austenitic stainless steels can be improved due to application of coated cutting tools. Hard PVD coating with low thermal conductivity and improved surface finish should be used in this case. This can result in enhancement of frictional characteristics at the tool/workpiece interface as well as chip evacuation process. In this study the stainless steel plates were machined using cemented carbide finishing end mills with four high aluminum containing PVD coatings namely: AlCrN, AlCrNbN, fine grained (fg) AlTiN and nano-crystalline (nc) AlTiN. Both AlTiN and AlCrN-based coatings have high oxidation resistances due to formation of aluminum oxide surface layers. The influence of surface post-deposition treatment on tool wear intensity was investigated. The coating surface texture before and after post-deposition treatment was analyzed by means of the Abbot-Firestone ratio curves. Minimal wear intensity after length of cut 150 m was achieved for cutting tools with the nc-AlTiN coating.     

Two distinct fracture modes of copper alloys in fluoride environments

The susceptibility of aluminum brass and aluminum bronze to stress corrosion cracking (SCC) was evaluated in fluoride environments by means of the slow strain rate technique. The effects of fluoride concentration and applied electrochemical potential on the SCC susceptibility were investigated. The SCC mechanism of aluminum brass was found to be dependent upon the de-alloying phenomenon while that of aluminum bronze on the film-rupture mechanism occurring within a certain range of applied electrochemical potentials. For aluminum brass, both the stress ratio and the time-to-fracture ratio were closely related to the logarithmic concentration of F⁻ ions. The fracture modes were ductile dimpled tearing fracture for the aluminum brass at the corrosion potential while intergranular for the aluminum bronze at various anodic potentials. The micro-galvanic effects of the constituent elements were used to estimate the anodic equilibrium potentials of the two alloys.     

含镍中间层铍青铜微电阻点焊接头形成机理

采用微电阻点焊对0.1 mm厚铍青铜薄片加入0.05 mm的镍中间层进行了搭接点焊,通过拉剪试验、光学显微镜、扫描电镜和能谱分析,研究了镍中间层对超薄铍青铜微电阻点焊接头形成过程和接头强度的影响. 结果表明,含镍中间层的超薄铍青铜微电阻点焊接头主要包括钎焊连接和熔化-钎焊混合连接机制. 其形成过程会经历铜合金润湿铺展、元素扩散、镍铜界面反应和金属凝固四个过程. 在这两种接头中,钎焊连接接头断裂方式为沿结合面断裂,熔化-钎焊连接接头断裂方式为纽扣断裂,断口都呈现韧性断裂与脆性断裂混合特征.     

Interface behavior study of WC92-Co8 coating produced by electrospark deposition

ESD (electrospark deposition) is a promising process to produce hard and wear-resisting coatings on metallic substrates. In this paper microstructure and inteorucial characteristics of the WC92-Co8 coated on titanium and carbon steel are presented. A metallurgical bonding between the coating and substrate is obtained. The Ti element was found to distribute in WC92-Co8 at the metal pool, as well as the interface by diffusion. Some new phases were produced in the coating layer due to the chemical reaction during the ESD process. Experimental observation and thermodynamic analysis were utilized to study the mechanism of ESD.     

Machining ferrous materials with carbides coated by chemical vapour deposition I: Interfacial conditions

In order to interpret the wear surfaces of uncoated cemented carbides and those coated by chemical vapour deposition (CVD), it is important to appreciate the nature of the interfaces formed between the tool, the forming chip and the newly created workpiece surface. To elucidate these conditions a series of quick-stop experiments and tool temperature estimates were made with coated and uncoated cemented carbide tools. Three distinct interfacial zones were observed: (a) the main chip-tool interface; (b) the peripheral chip-tool contact at the outer edges of the chip underside; (c) the flank- workpiece interface. These interfaces were essentially similar for CVD-coated and uncoated carbides, but the strength of bonding across the main chip-tool interface was greater for the uncoated carbides, which led to a larger chip- tool contact length and higher rake face temperatures for these tools when cutting steel.     

铝合金切削过程刀具磨损预测研究

为更精确地研究刀具磨损,建立刀具磨损模型至关重要。目前刀具磨损的模型主要是经典的刀具磨损模型和刀具磨损预测模型,刀具磨损预测模型主要为人工神经网络、隐马尔可夫模型和支持向量机模型。分析铝合金切削过程中的刀具磨损机制,总结经典的刀具磨损模型,梳理刀具磨损预测模型。铝合金切削过程中刀具主要的磨损机制为黏着磨损、扩散磨损和磨粒磨损。结果表明：在黏着磨损和磨粒磨损的基础上考虑扩散磨损的刀具磨损理论模型最接近实际加工。     

基于铬青铜超塑变形的铬青铜/钨合金固相焊接

探讨了在铬青铜超塑变形条件下实现铬青铜与钨合金固相焊接的可行性及影响因素 ,试验表明 ,将铬青铜与钨合金试样待焊表面认真清洗后对接 ,并施加 10～30MPa的预应力 ,然后在 740～ 80 0℃、初始应变速率 (1.6 7～ 13 .3)× 10 -4 s-1变形条件下恒温压接 3～ 10min即可实现接头剪切强度达铜基母材强度的固相焊接。焊接过程中铬青铜发生了超塑性流变 ,钨合金变形甚微 ,原界面两侧原子发生了明显扩散     

铜铝配套端面的精密磨削加工研究

为解决青铜衬套压入铝合金阀座后铜铝配套端面的高精密磨削加工难题,实现磨削后达到高精度尺寸误差和形位公差,通过对不同砂轮类型和不同磨削参数、不同磨削刃角度进行对比试验,得出了适用的磨削砂轮、磨削参数和磨削刃角度,实现产品合格率达到95%以上。     

Interface of solid steel and liquid aluminum under nonequilib rium diffusion

1　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｃｕｒｒｅｎｔｐｒｏｄｕｃｔｓｏｆｓｏｌｉｄｓｔｅｅｌａｎｄｌｉｑｕｉｄａｌｕｍｉｎｕｍｕｎｄｅｒｃｏｎｖｅｎｔｉｏｎａｌｄｉｆｆｕｓｉｏｎｍａｉｎｌｙｉｎｃｌｕｄｅｈｏｔｄｉｐａｌｕｍｉｎｉｚｉｎｇｓｔｅｅｌｐｌａｔｅ[1～3]ａｎｄｓｔｅｅｌａｌｕｍｉｎｕｍｓｏｌｉｄｔｏｌｉｑｕｉｄｂｏｎｄｉｎｇｐｌａｔｅ[4～6].Ｔｈｅｄｉｆｆｕｓｉｏｎｏｆａｌｕｍｉｎｕｍａｔｏｍｓｉｎｔｈｅｉｎｎｅｒｐａｒｔｏｆｓｏｌｉｄｓｔｅｅｌｂａｓｅｉｓｒａｔｈｅｒｓｕｆｆｉｃｉｅｎｔｎ…     

Fabricating Aluminum Bronze Rotating Band for Large-Caliber Projectiles by High Velocity Arc Spraying

The necessity of finding new rotating band materials and developing corresponding joining technologies for large-caliber projectiles has been revealed by the recent increase in the ballistic performance of high loads. In this paper, aluminum bronze coatings were fabricated by the high velocity arc spraying (HVAS) technique. Microstructure and microhardness of the prepared coatings were investigated. Ring-on-disk dry sliding wear tests were conducted in an ambient condition to examine the tribological behavior of the coatings. Quasi-static engraving processes of rotating bands made of as-sprayed aluminum bronze coating and bulk copper were studied using rate-controlled push test methodology on an MTS 810 Material Testing System. The results show that the as-sprayed aluminum bronze coatings have a dense microstructure with porosity of about 1.6%. Meanwhile, the as-sprayed coating presents a higher microhardness than pure copper. The friction coefficient of coatings is about 0.2-0.3 in the steady state. Tribological mechanisms of the as-sprayed coatings were discussed. The engraving test results show that the aluminum bronze rotating band presents high bonding strength and good plasticity. The HVAS aluminum bronze coating should be a possible substitute for the state-of-the-art copper rotating band.     

Machinability of bronze–alumina composite with tungsten carbide cutting tool insert

Bronze–alumina metal matrix composites have been attracting the interest of researchers in recent years, as they have many advantageous characteristics. The mechanical properties of the bronze–alumina composite are improved by the addition of alumina in the matrix. In this present work, bronze was reinforced with 10 wt% alumina particles. The bronze–alumina composite was prepared by stir-casting method. Preheated alumina particles were introduced into the vortex of the molten alloy created by a rotating impeller. Machining studies were conducted on bronze and bronze–alumina composite using tungsten carbide cutting tool insert. The flank wear of the carbide tools on machining bronze–alumina composite is higher than on machining bronze because of the abrasive characteristics of alumina. The cutting force during machining of bronze is lower when compared to that on machining bronze–alumina composite. The bronze exhibited slightly better surface finish than bronze–alumina composite.     

Ion exchange at a metal–ceramic interface

We present the results for an interfacial reaction between magnesium aluminate spinel and aluminum metal at 640 °C which, for the first time, show the occurence of ion exchange at a metal–ceramic interface. The exchange reaction occurs by the diffusion of magnesium and aluminum ions across the interface in opposite directions. The enrichment of the spinel in aluminum cations, and the metal in magnesium is confirmed by the appearance of phases of aluminum oxide and magnesium–aluminum intermetallics in the X-ray diffraction spectra. Electron spectroscopic images of spatial elemental distribution provide further evidence for the reaction. A drop in the thermal and electronic conductivities are explained by enhanced scattering of the electrons by solid solution Mg in the aluminum metal. The experiments were carried out on composites consisting of an aluminum matrix with a fine dispersion of spinel particles, whose size was varied while the volume fraction was held constant. Measurable ion exchange reaction was seen only in the composites containing the smaller (one micrometer size) particles. The influence of surface to volume ratio of the particles on the reaction rate confirms that the reaction was interface controlled. The possibility of a nucleation and growth process for the conversion of spinel into alumina and solid solution magnesium was ruled out by quantitative thermodynamic analysis.     

Tensile properties of some copper- and zinc-based alloys: Effects of strain rate and test temperature

This study analyzes the effects of test temperature and strain rate on the tensile properties of some copper-and zinc-based alloys. The copper-based alloys comprised a leaded-tin and an aluminum bronze, whereas the zinc-based alloys were added with various quantities of aluminum. The aluminum bronze attained maximum room-temperature tensile strength, whereas that of the leaded-tin bronze was the least. Among the zinc-based alloys, the one comprising 27.5 mass% aluminum exhibited superior tensile strength, followed by those alloyed with 11.5, 37.5, and 47.5 mass% aluminum in a descending order. Increasing strain rate tended to improve the tensile strength of the alloys. Tensile strength was reduced with an increase in test temperature irrespective of the alloy composition. The aluminum bronze possessed maximum strength regardless of temperature. The leaded-tin bronze attained least strength property at low temperatures, whereas higher test temperatures led to superior strength than the zinc-based alloys. The temperature sensitivity of the strength of the zinc-based alloys decreased with their aluminum content. Tensile elongation of the alloys tended to increase with an increase in strain rate and test temperature. Leaded-tin bronze was least affected in either case. The alloy also attained least elongation irrespective of test conditions. The aluminum bronze showed maximum elongation, at least at high strain rates. In the case of the zinc-based alloys, intermediate range of aluminum concentration led to better elongation. The elongation property of the alloys was affected by temperature in different manners. In a few cases, the elongation initially increased followed by a reduction beyond a specific test temperature, whereas, in other cases, a continuous increase with temperature was noted. The observations made have been discussed in terms of the nature of different microconstituents of the alloys whose effectiveness changes with test conditions. The response of the samples has been further substantiated with their fractographic features and subsurface characteristics.     

复合织构刀具切削铝合金的性能∗

基于铝合金材料切削的现状和需求,针对单一织构刀具存在的抗黏减摩性能不足的问题,将不同织构应用于刀-屑接触区域,提出刀具前刀面分区异构的思想。利用皮秒激光在刀具黏结区与滑移区分别加工凹坑和沟槽,并调整沟槽的取向(平行 / 垂直于主切削刃),得到上下型(SXDV 和 SXDP)和左右型(ZYDV 和 ZYDP)四种复合织构刀具。对 6061 铝合金进行湿切削试验,研究不同区域内添加不同织构对刀-屑接触表面摩擦状态的影响。研究结果表明,对比无织构和单一织构刀具, ZYDP 复合织构刀具展现了更好的切削性能。具体表现如下：与无织构刀具相比,ZYDP 刀具的主切削力降低 30.7%,刀面黏结面积减少 63.9%,切屑卷曲半径减少 27.4%。合理的复合织构方案可以明显改善刀具切削过程中的黏结磨损问题,延长了刀具寿命。复合织构方案的提出以及相应的激光加工过程可为织构刀具的设计及实际应用提供新思路。