均匀化处理对3004铝合金显微组织的影响

采用光学显微镜， 扫描电子显微镜， 透射电子显微镜， 电子探针Ｘ 射线微区分析仪和定量图像分析仪研究了３００４ 铝合金铸态和均匀化退火态的显微组织以及均匀化退火温度和时间对显微组织的影响。在铸态组织中发现了一种新的富ＭｇＳｉＣｕ 的共晶体。在均匀化退火过程中发生β→α相变和α弥散相的脱溶析出。在试验条件下， 最佳均匀化退火工艺为６１５ ℃，２０ ｈ 。经此工艺处理可获得较均匀的显微组织     

铸造SiC／钢基复合材料中粒子分布特点

实验观察发现，铸造ＳｉＣ／钢基复合材料中ＳｉＣ粒子大多数均分布在珠光体晶内，而分布在铁素体晶内的较少，分布在晶界上的粒子更少，由此推断出在钢液凝固时绝大多数ＳｉＣ粒子被奥氏体裹在了晶内，本文对此情况还从理论上进行了探讨。     

半连续铸造Al／AlSi梯度合金的热稳定性

采用双流浇注半连续铸造方法制备Ａ１／ＡＩＳｉ梯度合金。研究了合金高温退火处理后的组织和性能变化。结果说明：合金高温退火后的洛氏硬度比铸态时显著降低且沿试样横截面的梯度分布趋于平缓，但５００℃ｘ２４ｈ后，再延长退火时间，硬度值基本保持不变；高温退火处理后，Ａ１／ＡＩＳｉ梯度合金仍能保持宏观上硅浓度的梯度分布，与铸态时无明显的差别。     

表面复合铸造SiC／Al显微组织及界面现象初探

采用负压铸型在铝铸件表面形成一层ＳｉＣ／Ａｌ复合材料层，初步探讨了复合层的显微组织和ＳｉＣ－Ａｌ界面结合，表明复合层中，ＳｉＣ粒子分布均匀，与基体合金界面结合良好。     

颗粒增强铝基复合材料的组织与性能

用熔铸法制备了ＴｉＢ２和ＳｉＣ颗粒增强铝基复合材料,评价了ＴｉＢ２／Ａｌ和ＳｉＣ／Ａｌ复合材料的硬度,研究了增强剂的加入方式和体积分数对ＴｉＢ２／Ａｌ复合材料拉伸性能的影响;并用扫描电镜分析了复合材料的显微组织。结果表明,ＴｉＢ２颗粒对Ａｌ基体的增强效果比ＳｉＣ颗粒好,Ｔｉ,Ｂ化合物的增强效果优于ＴｉＢ２粉末,复合材料的力学性能随ＴｉＢ２体积分数增加而提高;用含Ｔｉ,Ｂ化合物的混合物增强的１．５％ＴｉＢ２／Ａｌ（体积分数）复合材料的热轧退火态性能为σｂ１６０．４ＭＰａ,δ１３．１％,铸态ＨＢ４５１ＭＰａ。ＳＥＭ观察结果表明,在铝基体中添加Ｔｉ、Ｂ化合物的混合物能在基体中原位生成ＴｉＢ２颗粒。     

Co薄膜中CoSi化合物相转变过程观察

Ｓｉ衬底上生长的Ｃｏ薄膜，经２５０，４５０，５００℃退火后．用电子显微镜对Ｃｏ／Ｓｉ界面处ＣｏＳｉ化合物的相转变进行了观察结果发现ＣｏＳｉ为多晶颗粒．ＣｏＳｉ相和基体无取向关系Ｃｏ／Ｓｉ界面在退火温度范围内的相变过程为：２５０─４５０℃４５０─５００℃Ｃｏ２Ｓｉ＋Ｃｏｓｉ─→ＣＯＳｉ─→Ｃｏｓｉ＋ＣｏＳｉ２     

冷模具钢渗扩氮复合强韧化研究

研究了渗扩氮等温淬火对Ｃｒ７Ｍｏ３Ｖ２Ｓｉ和Ｃｒ１２ＭｏＶ钢、渗扩氮冷待淬火对６０Ｓｉ２Ｍｎ钢的显微组织分布、显微硬度梯度曲线的影响。结果表明，Ｃｒ７Ｍｏ３Ｖ２Ｓｉ和Ｃｒ１２ＭｏＶ钢制冷模具经渗扩氮等温淬火复合强韧化及６０Ｓｉ２Ｍｎ钢冷模具经渗扩氮冷待淬火复合强韧化处理后的使用寿命显著提高。     

SiC／Al—4%Mg复合材料的组织特征及界面分析

试验观察发现，在ＳｉＣ粒子增强Ａｌ－４％Ｍｇ复合材料中，绝大多数ＳｉＣ粒子分布于α相的晶界，呈夫规则排列，少量留在α相晶粒内。本文对其进行了理论分析，并对ＳｉＣ粒子与ＳＡｌ基体的界面进行了微观观察和分析。     

Ti—Ni—Si纳米合金的制备和特性

Ｔｉ７０Ｎｉ２０Ｓｉ１０非晶合金在５００－８００℃范围内经１ｈ退火后，可形成平均晶粒度为８－１２０ｎｍ的纳米合金，Ｘ射线衍射（ＸＲＤ）和透射电镜（ＴＥＭ）的结果表明，不同平均晶粒度的纳米合金样品中，相的组成相同，即Ｔｉ２Ｎｉ和Ｔｉ５Ｓｉ３以及少量的α－Ｔｉ晶体相，显微硬度（ＨＶ）的测量表明，纳米合金样品的显微硬度值比铸态或非晶态样品高一倍左右。但是，随着平均晶粒度的减小，硬度值的变化并不满足线性的     

基于PM的SiCp/Al复合材料在热塑性变形时的组织变化研究

实验研究了基于ＰＭ的ＳｉＣｐ／Ａｌ复合材料在热塑性变形过程中显微组织的变化规律。结果表明：ＳｉＣｐ／Ａｌ复合材料在固态下的塑性变形是通过其铝合金基体的塑性变形来实现的;当铝合金基体塑性变形时,在ＳｉＣ增强颗粒和铝合金基体之间存在一种相互作用,迫使非等轴的ＳｉＣ增强颗粒通过转动的形式来调整其方位,形成ＳｉＣ增强颗粒在铝合金基体粒子边界上顺着变形方向的定向排列;同时铝合金基体的塑性变形受到ＳｉＣ增强颗     

Microstructure and wear resistance of low carbon steel surface strengthened by plasma melt injection of SiC particles

Low carbon steel Q235 sheets were processed with plasma melt injection (PMI) of SiC particles. The sheets were melted by a transferred plasma arc and injected with fine (178 to 250 μm) and coarse (420 to 840 μm) SiC particles. Microstructure of the specimens was investigated with scanning electron microscope (SEM), energy dispersion spectroscopy (EDS) and X-ray diffraction (XRD) analyzer. Micro-hardness of the specimens was tested. Dry sliding wear test was performed on the specimens with a W6Mo5Cr4 V2Co5 steel roller. The results show that microstructure of the specimen with fine SiC particles injected consists of iron-based matrix and pearlite. No SiC particles are found in the melted layer. Microstructure of the specimen with coarse SiC particles injected consists of iron-based matrix, pearlite and graphite. Some coarse SiC particles are found embedded on the top surface of the specimen. The wear resistance of low carbon steel can be improved with PMI of both fine and coarse SiC particles. Wear loss of the specimen with coarse SiC particles injected is lower than that of the one with fine SiC particles injected. The SiC particles protect the matrix from worn out by the counter part and increase the wear resistance of the specimen.     

45钢在超细SiC颗粒作用下的正向冲蚀行为*

选用超细SiC颗粒作为磨料,研究了韧性材料45钢在正向冲击条件下的冲蚀行为并与7075-T6铝合金对比。使用高强度磁铁捕获了45钢冲蚀磨屑,利用扫描电子显微镜(SEM)对冲蚀磨损后试样表面以及磨屑形貌进行观测;采用质量分析法,分析45钢在不同冲蚀条件下的失重情况与材料去除率;利用X射线应力测定仪,分析45钢在不同冲蚀条件下的表层及深度方向的残余压应力分布情况。结果表明,正向冲击条件下,韧性材料表面主要发生塑性变形,偏向堆积脊部还存在片层剥落的材料去除形式,超细磨料产生的材料去除率相对较小,材料去除率随磨料量的增加呈先增加后减小的趋势;表层应力随磨料量呈先增加后降低的趋势,微磨料冲蚀残余压应力的影响深度约为10μm。     

Al-SiC powder preparation for electronic packaging aluminum composites by plasma spray processing

Powders of pure aluminum (Al) with 55 and 75 vol.% SiC particles were ball milled in a conventional rotating ball mill with stainless steel and ZrO₂ balls for 1–10 h. The morphology and microstructure of the milled powders have been observed and analyzed by scanning electron microscopy (SEM) and energy dispersive x-ray (EDX). The milled powders were plasma sprayed onto a graphite substrate to obtain Al matrix composites with high SiC volume fraction. SiC particles in the milled powders existed in two forms; i.e., the combination of Al into composite powder and individual. Plastic Al particles were broken during ball milling, and fine Al particles can be coated onto the surface of SiC particles. Iron contamination in the milled powders occurred when stainless steel balls were used. The iron level can be effectively controlled by using ZrO₂ ball media. The milling efficiency by ZrO₂ balls is inferior to that by stainless steel balls. Longer milling time was required with ZrO₂ balls to achieve the same effect as obtained with stainless steel balls. SiC particles in the sprayed composites from the milled powders exhibited a reasonably uniform distribution and high volume fraction.     

等离子喷涂纳米SiCp/FeS复合涂层的摩擦学性能

用等离子喷涂法成功制备了SiCp/FeS复合涂层,SiC颗粒尺寸为纳米级,均匀分布于FeS基体,涂层和40Cr钢基体结合良好.研究了FeS涂层和SiCp/FeS复合涂层的摩擦学性能.结果表明,SiCp/FeS复合涂层兼具优良的减摩性能和耐磨性能.在干摩擦条件下,掺入质量分数为0.2和0.3的纳米SiC颗粒时,摩擦系数和FeS涂层接近,但表面磨损体积显著降低,降幅可达1个数量级;油润滑条件下,SiCp/FeS复合涂层的摩擦系数低于FeS涂层,复合涂层具有比FeS涂层更佳的减摩性能.     

SiC颗粒增强钢基表面复合材料及耐磨性研究

采用V-EPC铸渗方法,以Q235钢为母材,制备SiC颗粒增强钢基表面复合材料,研究其制备工艺及其冲蚀磨损特性。结果表明：通过添加剂的调整,可以制备出复合良好、表面平整的SiC颗粒增强钢基表面复合材料,其冲蚀磨损耐磨性可比Q235钢提高1.3倍以上。     

电冶熔铸SiC增强钢基复合材料的组织与性能

用电冶熔铸的方法制备4%SiC颗粒增强轴承钢复合材料,对其组织性能进行探索.实验结果发现:SiC颗粒在电冶熔铸工艺中发生分解,原始颗粒没有保留下来,溶入钢基体的Si和C原子在快速冷却下会发生原位反应重新生成细小的原位SiC;磨损试验发现,原位SiC的存在使基体硬度上升,复合材料的整体耐磨性比基体材料相比有明显改善,磨损机理以粘着磨损和磨粒磨损为主.     

Effect of Particle Size on the Microstructures and Mechanical Properties of SiC-Reinforced Pure Aluminum Composites

This article examined the effects of particle size and extrusion on the microstructures and mechanical properties of SiC particle-reinforced pure aluminum composites produced by powder metallurgy method. It has been shown that both particle size and extrusion have important effects on the microstructures and mechanical properties of the composites. The SiC particles distribute more uniformly when the ratio of the matrix powder size and SiC particle size approaches unity, and the smaller-sized SiC particles tend to cluster easily. The voids are found to coexist with the clustered and large-sized SiC particles, and they significantly decrease the density and mechanical properties of the composites. Extrusion can redistribute the SiC particles in the matrix and decrease the number of pores, thus make the SiC particles distribute more uniformly in the matrix, and enhance the interfacial bonding strength. The decrease in the SiC particle size improves the tensile strength and yield strength, but decreases the ductility of the composites.     

Study on cylindrical magnetic abrasive finishing using unbonded magnetic abrasives

The process principle and the finishing characteristics of unbonded magnetic abrasive within cylindrical magnetic abrasive finishing are described in this study. The unbonded magnetic abrasive is a mechanical mixture of SiC abrasive and ferromagnetic particles with a SAE30 lubricant. Iron grit and steel grit, for which three various particle sizes were prepared for both, were used as ferromagnetic particles, each of them being mixed with 1.2 and 5.5 μm SiC abrasive, respectively. Also, the finishing characteristics on surface roughness and material removal as well as their mechanisms were investigated. Experimental results indicate that steel grit is more suitable for magnetic abrasive finishing because of its superior hardness and the polyhedron shape. The variations of material characteristics on the work surface both before and after finishing were also investigated. Si content was increased obviously, however its corrosion resistibility decreased on a surface that was finished via steel grit mixed with SiC abrasive.     

Characterization of internal damage in a MMCp using X-ray synchrotron phase contrast microtomography

The initiation and development of damage inside a 6061 Al alloy reinforced with SiC particles has been studied during in situ mechanical tests using high resolution synchrotron X-ray tomography. The high coherence of the X-ray beam used improves the detection of reinforcements in the matrix as well as the detection of cracks. Qualitatively, the same damage mechanisms are observed at the surface and in the bulk of the sample, the rupture of the SiC particles being the dominant mechanism for the early stages of plastic deformation. Quantitatively, however, it is found that the geometrical characteristics of surface SiC particles differ from those of bulk particles and that the damage growth rate is larger inside the sample. This result can be understood in terms of elastic energy and normal stress levels in the SiC particles as calculated by finite element method (FEM) analysis.