微米SiCp增强铝基复合材料摩擦磨损性能研究

以微米级(14μfm)SiCp和微米级Al粉(100～200目)为原料，采用冷压烧结和热挤压方法制备出不同体积分数的微米SiCp增强Al基复合材料，研究了它的耐磨性能。结果表明在较高载荷下，SiCp的体积分数为1．5％和5．0％的SiCp／Al基复合材料耐磨性比市售挤压态锡青铜QSn6．5—0．4和纯Al高得多，且随SiCp含量增加，复合材料的耐磨性能提高；磨损表面形成Al基体 弥散分布SiCp的理想耐磨组织。     

Al基复合材料分形特性及其磨损特性的研究

以亚微米级(130nm)SiCp和(100～200)目(149～75μm)Al粉为原料,采用冷压烧结和热挤压方法制备出不同体积含量的微米SiCp增强Al基复合材料,研究了其分形特性和耐磨性能.结果表明:SiCp/Al基复合材料具有分形特性,SiCp/Al基复合材料耐磨性优于市售挤压态锡青铜QSn6.5-0.4和纯Al,且随SiCp含量增加,复合材料的分形维数增大,耐磨性能提高;磨损表面形成Al基体+孔隙+弥散分布SiCp的理想耐磨组织.     

基于MATLAB的铝基复合材料磨损表面分形特性研究

通过对亚微米SiCp增强铝基复合材料磨损表面的分形研究,探讨了亚微米SiCp增强铝基复合材料摩擦磨损特性与分形维数的关系。按照结构函数法,用MATLAB软件进行编程,得到复合材料双对数坐标图。研究表明,亚微米SiCp增强铝基复合材料具有分形特性,且其分形维数与材料的磨损量有关,随着磨损量的增加,分形维数亦趋于增大,且分形维数在1.6≤D≤1.9之间。     

SiCp粒径及含量对铝基复合材料拉伸性能和断裂机制的影响

采用冷压烧结和热挤压方法制备出不同体积分数(1.5%,5%)亚微米(130 nm)和微米级(14μm)的SiCp增强铝基复合材料,并对其拉伸性能及断口形貌进行了分析.结果表明:粒径为130 nm的SiCp增强的铝基复合材料抗拉强度随着体积分数的增加而提高,其断裂机制是在Al-SiC界面处的铝基体撕裂形成的空洞和裂纹扩展为主;而粒径为14μm的SiCp增强的铝基复合材料的抗拉强度随着体积分数的增加而降低,其断裂机制为部分SiCp的解理断裂并沿基体扩展的复合过程.     

软相尺寸对反贝壳复合材料压缩性能的影响

文章采用一步球磨结合真空热压工艺制备了由Al₂O₃/Al纳米复合材料(硬相)和纯铝(软相)构成的反贝壳结构复合材料,研究了软相尺寸(从微米级到亚微米级)对复合材料压缩性能的影响,并对其变形失效机制进行了分析。结果表明：在保持高失效应变的前提下,抗压强度随软相尺寸的减小而逐渐提高,尤其是从微米级减小到亚微米级时,抗压强度达到494 MPa,比微米级时至少提高60%;当软相尺寸为微米级时,复合材料中的裂纹萌生于软硬相界面处,并沿着界面-硬相-软相扩展,最终形成沿着与加载方向呈45°的宏观主裂纹。同时,软相可有效阻挡二次裂纹的扩展,当软相尺寸减小到亚微米级别时,裂纹萌生于软相变形带附近并沿着变形带-硬相扩展,逐渐演变成与加载方向呈±45°的均匀分散于整个复合材料的微裂纹,即软相尺寸从微米级减小到亚微米级时,增韧机制由软相对裂纹的阻挡转变为微裂纹的增殖和均匀分散。该研究结果为制备高强韧铝基复合材料提供重要参考价值。     

SiCp/Al功能梯度复合材料冲击韧性的研究

铝基碳化硅(SiCp/Al)功能梯度复合材料具有高比刚度、高耐磨性,制备工艺简单,成本低,性能和功能具有很好的设计性等优点。因此在航空航天、医学器材、机械耐磨部件等很多领域都有着研究和应用背景。文中对增强颗粒尺寸分别为6,9,11μm的SiCp/Al功能梯度复合材料的冲击韧性进行了研究。     

SiCp/Al复合材料旋转超声辅助磨削的试验研究

铝基碳化硅颗粒增强复合材料(SiCp/Al)有许多优异的特性,但其加工非常困难,限制了该种材料在工程中的应用。旋转超声辅助磨削加工非常适合中、高体分SiCp/Al复合材料的加工。针对增强体体积分数45%、增强颗粒尺寸3μm、基体材料A12的SiCp/Al复合材料进行了实验研究,分析了加工表面形貌、表面粗糙度和切削力随切削参数的变化规律。实验结果表明,工件加工表面质量较高,表面粗糙度Ra值在0.131~0.340μm之间;切削过程平稳,轴向切削力Fz值在23.33~51.31N。     

SiC_p/Al复合材料的超精密车削试验

试验研究了碳化硅颗粒增强铝基复合材料(SiCp/Al)的超精密车削加工性能.使用扫描电镜(SEM)对已加工表面、切屑及其根部、刀具前/后刀面磨损带进行观察,使用表面粗糙度轮廓仪对各种切削条件下的加工表面粗糙度轮廓进行测试分析.结果表明,该材料的加工表面常残留微孔洞、微裂纹、坑洞、划痕、残留物突起及基体材料撕裂等微观缺陷,刀具几何参数、切削速度、进给量、增强颗粒尺寸和材料体积分数是影响表面粗糙度的主要因素.由于切削变形区微裂纹动态形成的作用,超精密切削该材料时一般形成锯齿型切屑.刀具-工件的相对振动、基体撕裂增强颗粒拔出、破碎、压入等是该材料超精密车削表面形成的主要机制.单晶金刚石(SCD)刀具主要发生微磨损、崩刃、剥落和磨粒磨损,聚晶金刚石(PCD)刀具主要发生磨粒磨损和粘结磨损.结论表明SiCp/Al的超精密切削加工性较差,但通过选择合适的工艺参数,体积分数为15%的SiCp/2024Al加工表面粗糙度Ra可达24.7 nm.     

纳米硬质合金刀具切削Al/SiC_p复合材料的实验

针对SiC颗粒硬度高,切削Al/SiCp复合材料时刀具磨损剧烈,本文提出用具有较高硬度、韧性及良好抗磨损能力的WC-7Co制备纳米硬质合金刀具,并对Al/SiCp复合材料进行了切削实验。研究了纳米硬质合金刀具磨损机理和Al/SiCp复合材料的切屑去除机理,以及刀尖处后刀面磨损值。研究认为,纳米硬质合金刀具磨损的机理为SiC颗粒的微切削作用引起的磨料磨损,及SiC颗粒对刀尖刃口的高频、断续冲击引起的微崩刃及微破损;Al/SiCp复合材料的切削实质是断续切削;去除机理为切屑的崩碎去除;纳米硬质合金后刀面磨损值较普通硬质合金小30%～50%。实验表明,纳米硬质合金较普通硬质合金更适于加工Al/SiCp复合材料。     

快速砂型铸造用模具表面耐磨涂层的研究

研究适合快速砂型铸造用模具的表面涂层材料,该涂层材料由环氧树脂CYD-128、稀释剂660A和固化剂组成,并添加一定量的微米级Al2O3颗粒。在WTM-1E微型磨损实验机上研究该涂层的耐磨性能,并用扫描电镜和原子力显微镜分析磨损后的表面形貌。结果表明:随Al2O3颗粒含量的增加,复合涂层的摩擦因数逐渐增大,磨损率逐渐降低,当Al2O3颗粒质量分数为5%时,磨损率最低;随Al2O3颗粒含量的增加,复合涂层的磨损机制由黏着占主导逐渐转变为犁削沟占主导;采用该涂层材料处理后的快速砂型铸造用模具具有一定的耐磨性。     

Drilling characteristics of SiCp/Al composites with electroplated diamond drills

SiCp/Al composites are extensively used in aerospace, automotive, and civil applications, and the machining characteristic of SiCp/Al composites is an issue of great economic impact. This paper presents an experimental investigation of the drilling characteristics during machining of SiCp/Al composites with electroplated diamond drills; the drilling characteristics were evaluated in terms of drilling forces, tool wear, surface roughness, and entrance edge quality. Due to the very different machining properties between the SiC particles and Al alloy matrix, in a broader sense, the edge defect is defined as an undesirable effect generated at the edge of a workpiece after the machining process. The results demonstrate that with the increase of the drilling speed, both the thrust force and torques have no significant increase, while the surface roughness increased quickly. In addition, it is found that the formation of the entrance edge defects was associated with the varying of the drilling force and the electroplated diamond drills were subjected to an extremely rapid flank wear. The primary wear mechanism includes abrasive and adhesive wear of the flank face.     

Effect of Wettability Enhancement of SiC Particles on Impact Toughness and Dry Sliding Wear Behavior of Compocasted A356/20SiCp Composites

In this study, the effect of wettability improvement of SiCp on the impact and sliding wear behavior of A356/20 wt% SiCp composites produced by a compocasting technique has been investigated. The result showed an increase of incorporation and uniform distribution of SiCp in the A356 matrix by elimination of SiCp segregation. Desired bonding between SiCp and the aluminum matrix due to improved wettability resulted in enhanced properties in terms of improved impact toughness and wear resistance. This improvement was also associated with partial refinement of coarse eutectic silicon due to increased incorporation and distribution of SiCp reinforcements. The highest enhancement was obtained when 1% Mg was added into the melt in addition to pretreated SiCp. The impact toughness value increased by 10 and 26% and the wear rate decreased by 5 and 30% when the SiC was treated and when Mg was added, respectively, compared to as-received SiCp. The impact fracture surfaces showed fewer decohered and well-bonded SiC particles in A356–(SiC-treated-Mg) composite. The highest wear resistance of A356/SiCp composites was achieved by A356–(SiC-treated-Mg) composite for applied loads of 10 and 20 N compared to other fabricated composites. The worn surface revealed mild abrasion and adhesion wear mechanisms.     

添加少量纳米SiCp对铜基材料电学和摩擦学性能的影响

考察了添加少量纳米SiCp对铜基材料电学和摩擦学性能的影响。结果表明：添加少量纳米SiCp(体积分数为0．5％),轻微降低了铜基材料的导电率,显著提高了耐磨性,有效降低了铜／钢摩擦副之间的粘着作用和材料转移;130nm SiCp／Cu基复合材料的导电性和耐磨性都优于30nm SiCp／Cu基复合材料。     

SiCp/Al复合材料镀金工艺研究

SiCp/Al复合材料导电性差、膨胀系数低,尤其是不具备钎焊能力。为了满足封装壳体的良好钎焊性能,必须对其表面进行镀金改性处理。文中针对SiC体积分数高达60%以上的SiCp/Al复合材料进行镀金工艺研究,主要目的是解决镀金层与基材之间的结合力难题。通过工艺试验,采用工艺分步实施化学镀镍、热处理、电镀镍、电镀金步骤,得到的镀层表面光滑平整,没有明显的结瘤和夹杂,与基材的结合力强。该工艺作为SiCp/Al可焊性表面处理技术之一,对于其他铝基复合材料表面处理具有重要的参考价值。     

Experimental study of high-speed milling of SiCp/Al composites with PCD tools

In this paper, high-speed milling experiments on silicon carbide particle reinforced aluminum matrix (SiCp/Al) composites with higher volume fraction and larger particles were carried out using polycrystalline diamond (PCD) tools at dry and wet machining conditions. For comparison, a TiC-based cermet tool was also used in milling the same workpiece material at very low speed. Worn PCD and cermet tools were measured and extensively characterized by scanning electron microscopy at different machining conditions. Furthermore, the effect of cutting distance on milling force and surface roughness were also investigated. The results showed that the main tool wear mechanism in machining of this type of material was abrasion on the flank face, and it was verified that the TiC-based cermet tool was not suitable for machining SiCp/Al composites with higher volume fraction and larger particles due to the heavy abrasive nature of reinforcement.     

Fabrication and characterization of 7075 Al alloy reinforced with SiC particulates

7075 aluminum (Al) alloy as matrix and silicon carbide (SiC) as reinforcement has been identified since it has potential applications in aircraft and space industries because of lower weight to strength ratio, high wear resistance and creep resistance. Thorough investigations about the microstructure and characterization of Al alloy/SiC composite are needed so that metal matrix composites (MMCs) fabricated for aircraft and space industries are defect free and have sound microstructure. Objective of this research work are the fabrication and microstructural investigations of AA7075–SiCp MMCs. 7075 Al alloy is reinforced with 10 and 15 wt.% SiCp of size 20–40 μm by stir casting process. The resulting as-cast composite structures are analyzed using scanning electron microscopy, X-ray diffraction (XRD), differential thermal analysis, and electron probe microscopic analysis (EPMA). SiCp distribution and interaction with 7075 Al alloy matrix is studied. The 7075 Al alloy–SiCp composite microstructure showed excellent SiCp distribution into 7075 Al alloy matrix. In addition to this, no evidence of secondary chemical reactions is observed in XRD and EPMA analysis. Decomposition step in derivative thermogravimetric curve is seen at temperature of 1,257, 1,210, and 1,256 °C for 7075 Al alloy, AA7075/10 wt.%/SiCp (20–40 μm) and AA7075/15 wt.%/SiCp (20–40 μm) composites, respectively. So, these composites can be successfully used for applications where temperature does not exceed beyond 1,250 °C.     

高体积分数SiCp/Al复合材料旋转超声铣磨加工的试验研究

由于大量高硬度增强相SiC颗粒的存在,高体积分数铝基碳化硅（SiCp/Al）复合材料的机械加工十分困难。旋转超声加工被认为是加工这种材料的有效方法。通过超声辅助划痕试验,分析高体积分数SiCp/Al复合材料旋转超声铣磨加工的材料去除机理。在超声振动的作用下,材料中铝基体发生塑性变形,其表面得到夯实;SiC增强相被锤击成细小的颗粒而发生脱落,形成较大的空洞。由于材料加工的缺陷大多产生于SiC颗粒的去除过程中,SiC颗粒的去除方式对加工表面的质量起着决定性的作用,选择合适的工艺参数可以有效提高加工表面质量。旋转超声加工工艺特征试验表明,超声振动可有效降低切削力;主轴转速对轴向切削力的影响最大,其次是进给速度,切削深度对轴向切削力的影响较小;另外主轴转速对表面质量的影响效果也最大,并随主轴转速的增大表面粗糙度增大。因此在加工过程中,可以适当加大切削深度,在保证加工质量的基础上,选择较大的进给速度,在保证刀具寿命的前提下,选择合适的主轴转速,以获得较优的加工表面质量和加工效率。     

Selection of optimal process parameters in WEDM while machining Al7075/SiCp metal matrix composites

Aluminium metal matrix composites (MMCs) reinforced with silicon carbide particulate (SiCp) find several applications due to their improved mechanical properties over the conventional metals for a wide variety of aerospace and automotive applications. However, the presence of discontinuously distributed hard ceramic in the MMCs made them as difficult-to-cut materials for conventional machining methods. The wire electrical discharge machining (WEDM), as a widely adopted non-traditional machining method for difficult-to-cut precision components, found an appropriate metal removal process for MMCs to enhance quality of cut within the stipulated cost. While machining the advanced materials like MMCs, a clear understanding into the machining performance of the process for its control variables could make the process uncomplicated and economical. In light of the growing industrial need of making high performance-low cost components, the investigation aimed to explore the machining performance characteristics of SiCp reinforced Al7075 matrix composites (Al7075/SiCp) during WEDM. While conducting the machining experiments, surface roughness, metal removal rate, and wire wear ratio are considered the responses to evaluate the WEDM performance. Response surface methodology is used to develop the empirical models for these WEDM responses. SiC particulate size and volume percentages are considered the process variables along with pulse-on time, pulse-off time, and wire tension. Analysis of variance (ANOVA) is used to check the adequacy of the developed models. Since the machining responses are conflicting in nature, the problem is formulated as a multi-objective optimization problem and is solved using the Non-dominated Sorting Genetic Algorithm-II to obtain the set of Pareto-optimal solutions. The derived optimal process responses are confirmed by the experimental validation tests, and the results are analyzed by SEM.     

Modeling and optimization of Al/SiCp MMC machining using Taguchi approach

This paper presents the influence of process parameters like cutting speed, feed and depth of cut on flank wear (VBc) and surface roughness (Ra) in turning Al/SiCp metal matrix composites using uncoated tungsten carbide insert under dry environment. The experiments have been conducted based on Taguchi’s L₉ orthogonal array. Abrasion and adhesion are observed to be the principal wear mechanism from images of tool tip. No premature tool failure by chipping and fracturing was observed and machining was steady using carbide insert. Built-up-edge formation is noticed at low and higher cutting speed and at high feed combination and consequently surface quality affected adversely. The optimal parametric combination for flank wear and surface roughness are found to be v1–f1–d3 and v3–f1–d3 respectively and is greatly improved through Taguchi approach. Mathematical models for flank wear and surface roughness are found to be statistically significant.     

SiC_p/Al复合材料铣削残余应力的有限元分析

SiC_p/Al复合材料属于典型难加工材料,大量Si C颗粒离散分布其中,导致在铣削加工高体积分数SiC_p/Al复合材料时,加工表面容易出现应力分布不均现象,严重影响材料的稳定性。为了研究SiC_p/Al复合材料加工表面残余应力,通过ABAQUS有限元分析软件建立了SiC_p/Al复合材料三维铣削有限元模型,并分析了切削工艺参数对残余应力的影响。结果表明:切削速度对残余应力变化影响较小,每齿进给量对残余应力变化影响较大,所得结果与经验计算值吻合较好。