原位合成TiB2/Al2O3复相陶瓷显微组织的研究

采用自蔓延燃烧合成法在室温下的空气中制备出了TiB2/Al2O3复相陶瓷,通过X射线衍射(XRD)和扫描电镜(SEM)分析表明:大部分TiB2的形貌为规则的块状,晶粒细小,平均尺寸为几个μm,但也出现了TiB2枝晶和棒状晶。而Al2O3的颗粒较大(10~40μm左右),形状不规则,Al2O3的断口呈层片状,Al2O3和TiB2出现聚集现象。     

Study on squeeze casting of an in situ 5 vol.-% TiB2/2014 Al composite

Abstract

An in situ 5 vol.-% TiB₂/2014 composite was prepared by an exothermic reaction of K₂TiF₆, KBF₄ and Al melts. The effect of introduction of in situ formed TiB₂ particles on the squeeze-casting formability of the composite was discussed. The microstructural evolution and changes in the mechanical properties of the composite at different squeeze pressures were investigated. The results showed that a pouring temperature of 710°C, a die temperature of 200°C and a squeeze pressure of 90 MPa were found to be sufficient to get the qualified squeeze cast and maximum mechanical properties for an Al 2014 alloy. However, the pouring temperature, die temperature and squeeze pressure need to be increased to 780°C, 250°C and 120 MPa for the composite to get the qualified squeeze cast and maximum mechanical properties as a result of the effect of introduction of in situ formed TiB₂ particles on the solidification process, plasticity and fluidity of the composite. The microstructural refinement, elimination of casting defects such as shrinkage porosities and gas porosities and improved distribution of TiB₂ particles in the case of the composite result when pressure was applied during solidification. Compared with the gravity-cast composite, the tensile strength, yield strength and elongation of the squeeze-cast composite at 120 MPa increased by 21%, 16% and 200%.     

CeO2 induced dispersive distribution of TiB2 particles in in situ TiB2/Al composite

Abstract

The roles of CeO₂ additive during preparation of in situ TiB₂/Al composite, alleviating particle settlement in composite melt and significantly improving particle dispersion in final microstructure, are studied in this paper. It is evidenced that the CeO₂ additive reacts with Al melts to release Ce solute into the melts, and the released surface active Ce is absorbed in the Al/TiB₂ interfaces without any other reaction products. First principles calculations show that the interfacial energy of Al/TiB₂ interfaces is reduced owing to the presence of Ce in Al/TiB₂ interfacial area. Therefore, the wettability of molten Al on TiB₂ surface is increased and the dispersion of TiB₂ particles in Al matrix is eventually improved.     

Effects of SiC,Al2O3, and ZrO2 particles on the LBMed characteristics of Al/SiC,Al/Al2O3, and Al/ZrO2 MMCs prepared by stir casting process

The effects of SiC, Al₂O₃, and ZrO₂ particles on the characteristics of Al/SiC, Al/Al₂O₃, and Al/ZrO₂ metal matrix composites (MMCs) have been studied in the present research work. The comparison of machining characteristics has been done to analyze the behavior of various reinforced particles with the variation of laser machining variables. The output characteristics such as dross height and kerf deviation have been investigated and compared with each MMCs. SEM and XRD have been used for the investigation of morphological changes in the structure and agglomeration of reinforced particles. The crack and recast layer formation has been examined in the specimens of higher quantity of reinforced particles. It was observed that the MMC material reinforced with SiC particles has shown different behavior as compared to other MMC materials.     

原位化学法制备纳米ZrO2/Cu复合材料的研究

为了提高铜基复合材料的强度和电导率,采用具有良好机械性能和热物理性能的ZrO2(3%(摩尔分数)Y2O3)作为增强相,原位化学法制备了ZrO2纳米颗粒增强铜基复合材料,其主要制备工艺包括前驱复合粉体CuO、ZrO2的制备,经氢气还原得到ZrO2/Cu复合粉,再经过压制,真空烧结,复压等工序制得最后的样品.研究了制备工艺包括初压压力,烧结温度、时间对材料性能的影响;结果表明,在初压压力为550MPa,975℃烧结1.5h时,可得到最佳性能复合材料.透射电镜观察表明,在ZrO2/Cu纳米复合粉中,氧化锆纳米颗粒形状为圆形和四方形,平均尺寸约为20nm左右.纳米ZrO2在基体中分布均匀,细化了晶粒,提高材料硬度,使复合材料具有良好的综合性能.随着ZrO2含量的提高,密度、电导率降低,硬度升高.     

Low-cycle fatigue behavior of in situ TiB2/Cu composite prepared by reactive hot pressing

Copper-based composite reinforced with in situ TiB₂ particulates was prepared through reactive hot pressing of Ti, B and Cu powders. The formation of in situ TiB₂ particulates was verified by the X-ray diffraction technique. Tensile test showed that fine TiB₂ particulates were very effective to increase the tensile and yield strengths of copper at the expense of tensile ductility. Strain-controlled low-cycle fatigue measurements demonstrated that the in situ TiB₂/Cu composite exhibited essentially stable cyclic stress response behavior under small total strain amplitudes of 0.1–0.3%. However, this composite exhibited slight cyclic hardening under strain amplitude of 0.4%. Such cyclic hardening was more pronounced at a total strain amplitude to 0.6% due to the formation of dislocation cells and networks. Finally, the fatigue life data of the in situ TiB₂/Cu composite can be described by the Coffin–Manson equation.     

Wear behaviour of aluminium matrix TiB2 composite prepared by in situ processing

Abstract

The wear behaviour and microstructure of aluminium and Al-12Si alloy (A413) matrix composites containing 1 and 5 vol.-%TiB₂ particles have been investigated. The composites were prepared by an in situ reactive slag technique. The wear surfaces and wear products were studied after reciprocating and rolling - sliding tests. Wear resistance increased with increasing particle content, and the Al-12Si composites were more wear resistant than those with Al matrixes. The wear mechanisms are briefly discussed.     

脉冲磁场下原位合成TiB2/7O55铝基复合材料的组织和力学性能

脉冲磁场下,采用7055-(Al-3％B)-Ti剂体系熔体原位反应法成功制备TiB2/7055铝基复合材料.利用XRD、OM和SEM等测试技术研究了复合材料的相组成和微观组织,同时在电子拉伸试验机上测试了复合材料的拉伸性能.结果表明,磁场作用下,原位反应更快更充分,颗粒分布更均匀,生成的TiB2颗粒呈六边形或多边状,平均尺寸约为600nm,α-Al晶粒细化到约10～20μm,第二相由连续网格状分布转变为非连续性分布.复合材料的抗拉强度从310MPa提高到333MPa,延伸率从7.5％提高到了8.0％.     

Sliding wear behaviour of Al 6063/TiB2 in situ composites at elevated temperatures

A low cost system of Al 6063 ? xTiB₂ (x = 0, 5, 10 wt.%) in situ metal matrix composites (MMCs) were prepared by the reaction mixture of K₂TiF₆ and KBF₄ with molten alloy. These in situ prepared composites were characterized by using scanning electron microscope, X-ray diffractometer, and microhardness analysis. The dry sliding wear behaviour of the prepared composite was investigated by using a Pin on Disc method at different applied loads of 9.8, 19.6 and 29.4 N for various temperatures (100, 200 and 300 °C). The study at room temperature was also carried out for comparison purpose. The results indicate that the wear rate decreases with the increase in the weight percentage of TiB₂, while it increases with the increase in the applied load.     

Abnormal grain growth in in situ TiB2 particle-reinforced 7055 Al composites

Journal of Materials Science - Abnormal grain growth behaviors of in situ TiB2 particle-reinforced Al composites under two-step annealing are investigated in this study. Abnormal grain growth...     

稀土元素对原位合成TiB_2/Al复合材料组织和性能的影响

采用原位合成法研究稀土元素Ce,Sc,Er对TiB_2/Al复合材料TiB_2颗粒和基体组织的影响,并对复合材料的拉伸性能进行分析。结果表明,稀土元素的添加显著改善了复合材料的组织和性能。添加0.3%(质量分数)Sc和Er的复合材料的TiB_2颗粒分布相对均匀,稀土元素Er对基体合金的组织细化效果最显著,其次是Sc。添加稀土Sc和Er元素的复合材料拉伸强度较好,分别提高了32%和31%,添加稀土Er元素的复合材料伸长率最佳,提高了85%,因此,其拉伸性能也最佳。添加稀土元素Sc和Er后,复合材料的断裂形式为微孔聚集型的韧性断裂。稀土元素对复合材料的作用机理表现在两方面:一是稀土元素的添加改善了复合材料的润湿性,并抑制了TiB_2颗粒的团聚;另一方面,稀土元素的添加使得基体合金组织细化,从而提高了复合材料的拉伸强度。     

Investigation on in situ Al0.5FeSi0.5/Al composites prepared by transient liquid phase sintering

In situ Al_0.5FeSi_0.5/Al composites were prepared by transient liquid-phase sintering. The hardness and wear resistance of the composites were investigated with an XHV-1000 microhardness tester and an M-2000 wear tester. Results show that with increased sintering temperature and holding time, the in situ needle-like reinforcement is transformed into short, bar-like, massive particles. At a sintering temperature of 510 °C and holding time of 4 h, the reinforcement consists of short, bar-like Al_0.5FeSi_0.5; moreover, the hardness of the in situ Al_0.5FeSi_0.5/Al composites peaks to a value eight times that of pure aluminum and 2.5 times that of Al–Si alloy. Accordingly, the wear resistance of the composites is the highest, i.e., 6.6 that of pure Al and 4.5 times that of Al–Si alloy.     

Formation of TiB2 particles during dissolution of TiAl3 in Al–TiB2 metal matrix composite using an in situ technique

A new technique has been developed in an aluminum based metal matrix composite in order to reveal the mechanism of formation of TiB₂ particles by mixing molten master alloys i.e., Al–8Ti and Al–4B in the Ti:B weight ratio of 5:2. A composite containing fine TiB₂ particles produced by this technique. In this approach, the progress of In situ formation of TiB₂ was carried out using hot stage microscope, energy dispersive X-ray analysis, scanning electron microscopy and X-ray diffraction analysis. From the experimental observations obtained; it was proposed that the formation of TiB₂ particles occurred via diffusion of Boron atoms through TiAl₃ particles interface, thereby reacting to form fine TiB₂ particles. Studies indicate that since the primary TiB₂ particles on the surface of TiAl₃ are appreciably free and movable and because of boron diffusion across boundary layer towards TiAl₃, TiB₂ particles produced during growth with the primary ones formed agglomeration rings. A model was schematically developed to explain the formation of TiB₂.     

激光熔化沉积制备TiB+TiC/Ti6Al4V复合材料微观组织研究

激光熔化沉积制备的钛合金微观组织中常出现异常粗大的柱状晶粒,限制了其在复杂承力结构件方面的应用。为降低原始晶粒的尺寸,提高合金强度,本文基于原位自生反应原理,在Ti6Al4V粉末中添加少量的颗粒增强体B₄C得到混合粉末,并通过激光熔化沉积工艺制备出熔覆层以及多层钛基复合材料(TMC)。利用光学显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)和显微硬度仪等测试手段研究了B₄C的添加对Ti6Al4V合金微观组织的影响规律,并对其作用机制进行了分析。研究表明:B₄C的添加降低了原始β晶粒的尺寸,并强化了合金基体。当添加1wt.% B₄C颗粒时,晶粒的外延生长得到有效抑制,原始β晶粒开始出现柱状晶向等轴晶转变(CET)的趋势,柱状晶粒尺寸由原始的平均600 μm减小到50 μm。同时,B₄C与钛基体发生原位反应形成的混杂增强相TiB和TiC富集在晶界,构成三维网状结构,不仅限制了晶内α相的生长,同时也起到了第二相强化的作用,使基体的硬度较基材提高了15 %以上。     

Property-microstructure correlation in in situ formed Al2O3, TiB2 and Al3Ti mixture-reinforced aluminium composites

The in situ formed Al₂O₃, TiB₂ and Al₃Ti mixture-reinforced aluminium composites were successfully fabricated by the reaction sintering of the TiO₂-B-Al system in a vacuum. With increasing boron content in the TiO₂-B-Al system, the amount of generated TiB₂ in the composites increased and Al₃Ti content decreased. At the same time the distribution uniformity of the in situ formed Al₂O₃ and TiB₂ particulates was obviously improved, and the size of the Al₃Ti particles was reduced. The in situ Al₂O₃ and TiB₂ particulates had sizes from 0.096–1.88 m. The interface between the in situ formed particulates and the aluminium matrix was clean, and no consistent crystallographic orientation relationship was found. The strength and elastic modulus of the composites was significantly improved by lowering the Al₃Ti content. When the boron content in the TiO₂-B-Al system rose, the morphology of the tensile fracture surface of the composites was changed from large fractured Al₃Ti blocks and fine dimples, to fine dimples and pulled-out particulates. The strengthening and fracture of the composites have been modelled.     

TiB2/Al复合材料制备工艺的研究进展

TiB2/Al复合材料是一种很有潜力的复合材料,在耐磨、航天航空等领域有着广阔的应用前景.目前TiB2/Al复合材料的制备工艺方法主要为原位自生法,如自蔓延高温合成、原位反应生成法、接触反应法和机械合金化法等,而粉末冶金法、喷射沉积法以及挤压铸造法等也逐渐被用于制备TiB2/Al复合材料.主要综述了目前国内外TiB2/Al复合材料制备工艺的研究进展,并对不同工艺的制备过程及利用该工艺所制备的TiB2/Al复合材料的情况进行了详细论述,指出了各种制备工艺的优缺点,展望了其研究趋势.     

TiB2的含量对Al2O3／TiB2陶瓷材料的高温氧化行为的影响

研究了不同ＴｉＢ２含量的Ａｌ２Ｏ３／ＴｉＢ２陶瓷材料的高温氧化行为。用ＸＲＤ和ＳＥＭ分析材料氧化后的相组成及显微结构，探讨了该材料的氧化机理和氧化膜的破坏方式。结果表明，不同ＴｉＢ２含量的Ａｌ２Ｏ３／ＴｉＢ２陶瓷材料在１４００℃空敢中氧化３０ｈ的氧化增重符合抛物线规律。     

AlNP/Al和TiB2P/Al复合材料摩擦磨损性能研究

研究了油润滑条件下两种不同铝基复合材料及其基体合金的摩擦磨损性能,分析了增强体对材料摩擦磨损性能的影响以及相应的磨损机理.结果表明:油润滑条件下,随着摩擦时间的延长,AlNP/Al复合材料的摩擦系数由小变大趋于稳定;而TiB2P/LY12复合材料的摩擦系数却是由大变小趋于稳定,这主要与其摩擦过程中形成凹坑产生润滑油膜有关.由于增强体强度的增加,50%(体积分数,下同)TiB2P/Al复合材料的摩擦系数低于50%AlNP/Al复合材料,且耐磨性优于50%AlNP/LY12复合材料.增强相的加入显著提高了材料的耐磨性,使得复合材料的抗粘着能力明显优于基体合金.     

TiB2/Al复合材料的组织性能研究进展

TiB2/Al复合材料是一种很有潜力的复合材料,在耐磨、航空航天等领域有着广阔的应用前景.复合材料的性能除了取决于基体和增强体外,还与制备材料所用的工艺有关.综述了采用不同工艺制备的TiB2/Al复合材料的显微组织、力学性能和摩擦磨损性能,详细介绍了采用不同工艺制备出的TiB2/Al复合材料组织性能的特点,并展望了其研究趋势.