SiC颗粒增强铝基复合材料切削表面分形维数及其与抗磨损性能的关系

做为一种耐磨性能很好的材料 ,SiC颗粒增强铝基复合材料切削加工表面具有分形特征。实际研究表明SiC颗粒增强铝基复合材料切削加工表面分形维数与抗磨损性能有密切关系 ,本文还分析了表面分形维数越大其抗磨损性能越强的机理。     

SiC颗粒增强铝基复合材料切削表面分形维数及其与抗磨损性能的关系

做为一种耐磨性能很好的材料，SiC颗粒增强铝基复合材料切削加工表面具有分形特征，实际研究表明SiC颗粒增强铝基复合材料切削加工表面分形数与抗磨损性能有密切关系，本文还分析了表面分形维数越大其抗磨损性能越强的机理。     

不同颗粒度SiC增强铝基复合材料的切削加工性能与适用刀具

铝基复合材料中增强粒子的大小对复合材料的切削加工性能影响极大，本文研究了不同颗粒度碳化硅颗粒对铝基复合材料切削加工性能的影响。并分析了不同颗粒度碳化硅增强铝基复合材料所适用的刀具。探讨了切削刀具对不同大小颗粒碳化硅增强铝基复合材料的切削机理     

碳化硅晶须增强铝复合材料的精密切削研究

对挤压铸造法制造的碳化硅晶须增强铝复合材料(SiCw/Al)进行的精密切削研究结果发现;一方面这种复合材料对刀具磨损较为严重;另一方面复合材料切削表面质量主要取决于进给速度,随进给速度提高,复合材料表面质量下降。研究还发现由于复合材料切削过程中特殊的金属去除机制,使复合材料切削表面均产生残余压应力。     

ZA22/Al2O3复合材料切削加工表面质量的研究

采用硬质合金刀具研究了挤压铸造Al₂O₃短纤维强化ZA22合金复合材料的切削加工表面质量。发现在相同切削条件下,该复合材料表面质量优于ZA22合金。高的切削速度、低的进给量及低的切削深度有利于提高该复合材料的切削加工表面质量。随Al₂O₃纤维体积分数增大,复合材料切削加工表面粗糙度降低。     

不同颗粒度SiC增强铝基复合材料的切削加工性能与适用刀具

铝基复合材料中增强粒子的大小对复合材料的切削加工性能影响极大，本文研究了不同颗粒度碳化硅颗粒对铝基复合材料切削加工性能的影响，并分析了不同颗粒度碳化硅增强铝基复合材料所适用的刀具，探讨了刀具对不同大小颗粒碳化硅增强铝基复合材料的切削机理。     

用立方氮化硼刀具对硬质合金材料进行延性超精密加工

对单相晶体结构和硬质合金的粘合特性的理论分析表明，对其进行延性超精密加工是可行的，并在普通加工中心上通过对切削力的监控，用立方氮化硼刀具实现了对硬质合金材料的延性超精密加工．研究结果显示，在用不同刀具进行的切削中，刀具的磨损都非常小；在对硬质合金的延性超精密加工中获得了纳米级表面粗糙度的平滑表面和层状切屑。     

复合材料的切削加工表面结构与表面粗糙度

普通金属材料的切削加工理论表面粗糙度可以用公式计算。复合材料经切削加工后其表面留有各种凹凸缺陷,这些谷峰轮廓并非由刀刃直接切出,故不宜用现有普通材料的公式计算其理论表面粗糙度。纤维增强复合材料的切削加工表面结构和粗糙度与切削方向密切相关。颗粒增强复合材料无方向性,其已加工表面结构和粗糙度主要受增强颗粒硬度和粒度以及含量控制。增强体与基体的界面强度及切削刀具和工艺条件对复合材料加工表面粗糙度有很大影响。      

聚晶金刚石研磨工艺研究新突破介绍

聚晶金刚石（PCD）具有接近天然金刚石的硬度、耐磨性以及与硬质合金相当的抗冲击性，是一种被广泛应用于有色金属和非金属材料精密加工的新型刀具材料。为充分发挥PCD刀具的优良性能，提高加工零件的表面质量，刀具前刀面（PCD表面）需加工成镜面。目前，PCD镜面通常采用树脂基金刚石砂轮进行研磨加工，但由于PCD与所用的金刚石磨料硬度、性质相近，因而与传统的研磨加工有着很大的不同，     

切削SiC增强铝基复合材料时刀具的磨损形态及机理

为研究切削SiC增强铝基复合材料时刀具的磨损形态和机理,采用硬质合金和聚晶金刚石(PCD)刀具进行了各切削工况下的切削试验。用爆炸式快速落刀装置获取切屑根,研究了前刀面的磨损部位。借助扫描电子显微镜(SEM)和原子力显微镜(AFM),检测分析了前、后刀面的磨损形态和成分组成,并进一步研究了磨损机理。结果表明:切削刀具的主要磨损部位发生在后刀面,磨损机理是磨料磨损;前刀面临近刃口区域首先产生由SiC增强相引起的磨料磨损,该区域随后由机械镶嵌生成积屑瘤,积屑瘤脱落后导致产生黏结磨损。黏结磨损的程度较轻,没有形成月牙洼型。前刀面离刃口稍远的区域(积屑瘤尾部后面)会同时产生由切屑底层SiC增强相引起的再次磨料磨损,磨料磨损的主要机理是"微切削"。     

Analysis of Surface Integrity in Drilling Metal Matrix and Hybrid Metal Matrix Composites

Hybrid metal matrix composites consist of at least three constituents-a metal or an alloy matrix and two reinforcements in various forms, bonded together at the atomic level in the composite. Despite their higher specific properties of strength and stiffness, the non homogeneous and anisotropic nature combined with the abrasive reinforcements render their machining difficult. In this paper, the surface integrity of machining in drilling hybrid composites has been discussed. Drilling tests are carried out at different spindle speed, feed rates, and different drill tool materials to investigate the effect of the various cutting parameters on the surface quality and the extent of the deformation of drilled surface due to drilling. Materials used for the present investigation are Al356/10SiC (wt%) metal matrix and Al356/10SiC-3mica (wt%) hybrid composites. The composites are fabricated using stir casting route. The drilling tests are conducted on vertical computer numeric control (CNC) machining center using carbide, coated carbide and polycrystalline diamond (PCD) drills. The surface roughness decreases with increasing spindle speed and increases with increasing feed rate. The machined surface is analyzed by scanning electron microscopy (SEM). SEM images of the machined surfaces indicate the presence of grooves and pits. Microhardness depth profiles indicate that the subsurface damage is limited to the top of 100-250 μm.     

FABRICATION OF SiCp-AI COMPOSITE MATERIALS

Liquid phase fabrication methods for aluminum matrix composites reinforced with SiC whiskers, or SiC particles have been investigated and the mechanical properties of fabricated composites have been evaluated. Three kinds of liquid phase fabrication methods; hot extrusion, hot pressing and pressure infiltration, were studied. Commercial SiC whiskers and SiC powders of alpha type and beta type were used as the reinforcements for an aluminum matrix. Among the fabrication methods investigated, the best results were achieved by the pressure infiltration. The mechanical properties and the wear resistance of the fabricated composites were measured. The SiC whisker reinforced aluminum matrix composites have high strength, so that they can be used as high specific strength materials. The SiC particulate reinforced aluminum matrix composites are not strong as the SiC whisker reinforced composites. However, the SiC particulate reinforced aluminum matrix composites have a good potential for use as wear resistant material. The hardening effect of beta type particles on the aluminum matrix was larger than that of alpha type particles.     

PCD刀具加工SiC颗粒增强铝基复合材料的合理切削速度

通过用扫描电镜等方式检测ＰＣＤ刀具的性能,并与天然金刚石的相关参数进行比较,阐明了ＰＣＤ的优异性能,通过ＰＣＤ刀具对碳化硅高比强颗粒增强铝基复合材料的试验,考察了切削速度对切削力、切削温度、刀具耐工和切削长度的影响,总结出高硅铝基复合材料切削中的合理切削速度。指出、在一定的切削条件下,当切削速度Ｖ＝３０－４０ｍ／ｍｉｎ时,可获得良好的综合效益。     

Wire electrical discharge machining of Al2O3 particle and short fibre reinforced aluminium based composites

Abstract

The wire electrical discharge machining behaviour of alumina particle and short fibre reinforced aluminium based composites was studied. Under the two cutting conditions of this study, namely coarse and fine cutting, the average surface roughness R_a of the particle reinforced composite was found always to be higher than that of the corresponding machined matrix surfaces, however, the opposite was found to be true for the fibre reinforced composite. Comparing the surface quality of the two composites, in terms of roughness measurements, the fibre reinforced composite was superior to the particle reinforced composite. Although cutting conditions have little effect on the overall R_a of the two composites, their corresponding surface topographies were found to be intrinsically different. Surface banding was observed on the fine cut surfaces of the particle reinforced specimens, which was believed to be caused by shifting of the wire. Based on the machined surface morphology and the measured surface profiles, the material removal mechanism for the two reinforced composites is discussed.

MST/3412     

SiC 颗粒增强铝基复合材料制备及机加性能研究

采用真空搅拌铸造法制备了20vol%SiC 颗粒增强A 356 基复合材料。SiC 颗粒在基体中分布均匀, 材料抗拉强度319M Pa, 弹性模量98. 9GPa, 延伸率1. 4%。采用聚晶金刚石-PCD 刀具, 在切削速度v= 30～ 40m/m in时, 复合材料对刀具损耗最小, 工件表面粗糙度良好。      

Spanende Bearbeitung von Bauteilen aus Al‐Matrix‐Verbundwerkstoffen

Machining of Components of Al Matrix Composites The microstructure of metal matrix composites consists of hard reinforcements which are embedded in a metal matrix. The high hardness of the reinforcements leads to a difficult processing of these materials. The present paper demonstrates the machining of components of Al matrix composites for the automotive and the aircraft industry. The components are SiC particle reinforced brake drums, cylinder blocks with local Si particle and Al₂O₃ short fiber reinforced cylinder liners and TiB₂ particle reinforced extrusion molding profiles. The investigations illustrate that good results can be achieved when machining these components by turning, boring, drilling and milling with polycrystalline diamond (PCD) or CVD diamond thick‐film cutting tool materials.     

Studies on machinability of Al/Si<Subscript>p</Subscript> + SiC<Subscript>p</Subscript> composite materials

This paper presents the experimental results on the machinability of silicon and silicon carbide particles (SiC_p) reinforced aluminium matrix composites (Al/Si_p + SiC_p) during milling process using a carbide tool. The total volume fraction of the reinforcements is 65 vol%. The milling forces, flank wear of the tool and the machined surface quality of composites with different volume fraction of SiC_p were measured during experiments. The machined surfaces of composites were examined through SEM. The results showed that the flexural strength and Vickers hardness are improved when certain volume fraction of silicon particles are replaced by silicon carbide particles with the same volume fraction and particle size and the effect of SiC_p on machinability is optimal when 9 vol% silicon particles in Al/Si_p was replaced by silicon carbide particles with the same volume fraction and the same particle size. Cracks and pits were found on the machined surfaces of composites due to the intrinsic brittleness of silicon particles.     

Influence of material swelling on surface roughness in diamond turning of single crystals

Abstract

The effect of material swelling on the surface roughness in ultraprecision diamond turning has been investigated. Experimental results from the power spectrum analysis indicate that the profile of the tool marks is distorted by the effect of swelling of the materials being cut. A good correlation exists between the surface roughness and the amount of swelling that has occurred in the machined layer. Radically different surface roughness profiles were obtained when machining aluminium and copper single crystals with the same cutting plane and tool shape. The difference in the machining behaviour could not be accounted for by elastic recovery alone but could be explained by considering the plastic deformation induced in the machined layer.     

碳化硅增强铝基复合材料界面改善对力学性能的影响

用粉末冶金法制备了致密度较好的镀铜碳化硅增强铝基复合材料,并对碳化硅的表面化学镀工艺进行了分析.通过化学镀前后复合材料力学性能的对比研究表明,碳化硅表面镀铜较好地解决了碳化硅与基体的相容性问题,使复合材料的力学性能得到明显提高.