保温时间对瞬时液相扩散连接的Ti3Al /Ti2AlNb接头微观结构及力学性能的影响

采用Ni-Ti复合箔片作为中间层,在990 ℃、低连接压力（0.1 MPa）下,通过瞬时液相（TLP）扩散连接制备了Ti₃Al/Ti₂AlNb异种合金接头。分析了保温时间（10~90 min）对Ti₃Al/Ti₂AlNb接头微观结构及力学性能的影响,并研究了TLP扩散连接接头的界面演变和形成机制。结果表明,Ti₃Al/Ti₂AlNb接头具有典型的“Ti₃Al | Al_0.5Nb_0.5Ti₃ | 残余 Ni | NiTi | NiTi₂ | 残余 Ti | Al_0.5Nb_0.5Ti₃ | Ti₂AlNb”多层梯度结构。随着保温时间的延长,接头的抗剪切强度先增大后减小,当保温时间达到60 min时,Ti₃Al/Ti₂AlNb接头的抗剪切强度最大,达到167±12 MPa。另外,接头的断裂主要发生在Ti₂AlNb/Ti附近的NiTi₂层,并向Ti层延伸,呈现出脆性断裂的特征。     

Ti 元素对B4C/Al复合材料力学性能的改善作用研究

B₄C/Al复合材料是目前最理想的中子吸收材料,广泛用于乏燃料储存。本文利用液态搅拌法制备B₄C/Al复合材料,通过添加Ti元素,探讨了界面反应对材料的界面结构和力学性能的影响。研究发现,Ti元素通过参与界面反应,改变了界面结构,在B₄C颗粒表面形成了紧密结合的纳米TiB₂界面层;Ti的添加消除了界面微裂纹、微孔、分离等缺陷。随着界面反应程度的加强,材料强度提高,尤其反应脱落的纳米TiB₂颗粒作为原位第二强化相进一步增强基体。B₄C/Al复合材料断裂过程表现为韧窝延性断裂;TiB₂界面层增强了B₄C颗粒与基体的结合,断裂行为从B₄C-Al界面脱落转变为B₄C颗粒断裂;但过渡的界面反应会形成微韧窝,引起材料延伸率下降。     

Ti3AlC2掺杂SPS法制备Ti2AlC/TiAl复合材料的研究

通过2TiC-Ti-1.2Al体系的原位热压反应制备了Ti₃AlC₂陶瓷,然后以59.2Ti-30.8Al-10Ti₃AlC₂(wt%)为反应体系,采用放电等离子烧结技术制备出Ti₂AlC/TiAl基复合材料。借助XRD、SEM分析了产物的相组成和微观结构,并测量了其室温力学性能。结果表明：原位热压烧结产物由Ti₃AlC₂和TiC相组成,Ti₃AlC₂呈典型的层状结构,TiC颗粒分布在其间。SPS法制备的Ti₂AlC/TiAl基复合材料主要由TiAl、Ti₃Al和Ti₂AlC相组成,Ti₂AlC增强相主要分布于基体晶界处,表现为晶界/晶内强化作用。力学性能测试表明：Ti₂AlC/TiAl基复合材料的密度、维氏硬度、断裂韧性和抗弯强度分别为3.85 g/cm₃、5.37 GPa、7.17 MPa?m_1/2和494.85 MPa。     

SiCf/Ti-60热稳定性研究

本文对采用磁控溅射先驱丝法制备的SiC_f/Ti-60复合材料进行不同温度下长时间热暴露实验,分析了热等静压态和热暴露态复合材料界面区结构稳定性及元素扩散规律。研究结果表明,界面反应层主要产物为TiC,纤维中C、Si元素和基体中Ti及其它合金元素进行互扩散;C元素扩散速率较快,在界面处和基体内形成TiC,基体中的TiC主要集中分布在α相晶界处。SiC_f/Ti-60复合材料反应层长大受扩散控制并遵循抛物线定律,界面反应层长大指数因子为2.27×10_-4 m/s_1/2,界面反应层长大激活能为118 kJ/mol。     

La2O3含量对搅拌摩擦加工制备Ni /Al复合材料组织和性能的影响

采用搅拌摩擦加工方法在Al基体中添加不同La₂O₃含量的混合粉末(Ni+La₂O₃),制备 (Ni+La₂O₃)/Al复合材料。采用SEM、EDS、 EPMA及XRD对复合区微观结构及相组成进行分析,采用室温拉伸试验对 (Ni+La₂O₃)/Al复合材料力学性能进行了测试。结果表明,随着La₂O₃含量的增加,(Ni+La₂O₃)/Al复合材料的组织和性能先变好后变差。当La₂O₃添加量达到5%时,复合材料中Al₃Ni增强颗粒分布均匀、颗粒数量最多,块状的Ni粉团聚减少,其抗拉强度达到最大值215MPa,相比Ni/Al复合材料(抗拉强度176MPa),其抗拉强度提高了22%;当La₂O₃的添加量为7%时,复合材料中Al₃Ni增强颗粒含量减少,块状Ni粉团聚重新出现,抗拉强度下降至201MPa。     

Ti活度对Al2O3/AgCuTi/Fe-Ni-Co钎焊接头机械性能和微观组织结构的影响

采用AgCuTi钎料实现了Al₂O₃陶瓷与Fe-Co-Ni合金的钎焊连接,并调查了不同钛含量的钎料对Al₂O₃/AgCuTi/Fe-Ni-Co钎焊接头机械性能和微观组织结构的影响。扫描电子显微镜(SEM), X射线能量色散光谱仪(EDS), X射线衍射仪(XRD)及电子万能试验机用于分析钎焊接头的机械性能和微观组织结构,结果表明:钛含量的增加明显提高AgCuTi钎料与Al₂O₃陶瓷的相互作用,在Al₂O₃/Ag-Cu-Ti界面生成一层由Ti-Al 和 Ti-O化合物组成的反应层。Al₂O₃/AgCuTi/Fe-Ni-Co钎焊接头的抗拉强度随钛含量的增加而增加,当钛含量提高到8wt.%时,抗拉强度达到最大值78Mpa。通过微观组织结构分析发现,采用AgCu4Ti在890℃保温5min的条件下可以获得较好的钎焊接头,典型接头的微观组织结构为Al₂O₃/TiAl+Ti₃O₅/NiTi+Cu₃Ti+Ag(s,s)/Ag(s,s)+Cu(s,s)+(Cu,Ni)/Fe-Ni-Co。采用AgCu8Ti获得的钎焊接头的界面反应层与AgCu4Ti差异不大,但反应层稍微增厚,并伴有TiO和Ti3Al在Al₂O₃/Ag-Cu-Ti界面生成。     

含微纳B4C/Ti颗粒铜基复合材料的微观组织与力学性能

采用高能球磨(HEBM)和放电等离子烧结(SPS)工艺成功制备出微纳B₄C/Ti颗粒增强铜基复合材料(CTBCs),通过X射线衍射(XRD)、光学显微镜(OM)、扫描电子显微镜(SEM)以及能谱(EDS)等测试手段对其微观组织形貌进行表征。结果表明,(B₄C+Ti)颗粒在基体中均匀分布,增强体与铜基体界面结合良好,且其结合形式为冶金结合和机械结合并存。采用阿基米德排水法测定出烧结态试样的致密度。复合材料的显微硬度、拉伸屈服强度、抗拉强度和延伸率等力学性能相较于纯铜试样得到显著提高,这主要归因于载荷传递、细化晶粒与热错配等强化机制。复合材料的拉伸断口表现出明显的韧性断裂特征。     

SiC_P/7085复合材料制备工艺及实验研究

采用半固态金属-增强相混合工艺制备SiC颗粒体积分数为10%的SiC_P/7085铝基复合材料,研究微米SiC颗粒在机械搅拌、超声搅拌和复合搅拌等工况下在7085铝基体中的分布规律以及不同制备工艺对SiC_P/7085复合材料拉伸性能的影响规律。结果表明:机械搅拌能够改善颗粒分布的均匀性,但同时会增加气孔缺陷;超声搅拌能有效减少复合材料中的气孔数量;采用复合搅拌工艺(30min机械搅拌+30 min超声搅拌)制备的SiC_P/7085复合材料颗粒分布均匀、气孔显著减少,抗拉强度较基体合金有较大提高,其中SiC颗粒尺寸为80、30μm的复合材料的最大抗拉强度较基体分别提高了57%和67%。     

原位内生颗粒增强TiB_2/7055铝基复合材料的组织

对原位内生Ti B2/7055铝基复合材料的微观组织和热处理特性进行了研究。结果表明,原位内生的Ti B2颗粒在基体中弥散分布,与基体界面结合良好。Ti B2/7055复合材料具有显著的时效强化行为,增强相Ti B2颗粒促进复合材料的时效析出行为,缩短硬度达到峰值的时间,热处理后硬度和抗拉强度等性能明显提高。确定了12 mass%Ti B2/7055复合材料最佳热处理制度为460℃固溶60 min,120℃时效20 h。     

SiCp颗粒含量对SiCp/ Mg–5Al–2Ca复合材料组织与性能的影响

本研究通过搅拌铸造法制备了三种不同体积分数(2%,5%, 10%)的SiCp/Mg–5Al–2Ca复合材料,并在673 K下进行了热挤压。铸态复合材料中,少量SiCp颗粒的加入就能破坏了Al₂Ca相沿基体合金晶界分布并有效细化Al₂Ca相析出尺寸。随着SiCp体积分数的增高,Al₂Ca相尺寸有所降低,但不明显。经过热挤压后,Al₂Ca相破碎并沿挤压方向排布,基体合金晶粒得到细化。晶粒尺寸以及Al₂Ca相尺寸随着SiCp体积分数的增高呈微小降低。与单组元基体合金相比较,挤压态SiCp/Mg–5Al–2Ca复合材料的屈服强度和加工硬化率随着SiCp体积分数的增高而逐渐增高,而延伸率则逐渐下降;抗拉强度最大值则出现在SiCp体积分数为5%时。复合材料中SiCp颗粒以及Al₂Ca相的脱粘以及开裂是导致复合材料断裂的主要原因。     

Microstructure and mechanical properties of extruded Al/Al2O3 composites fabricated by stir-casting process

A novel two step mixing method including injection of particles into the melt by inert gas and stirring was used to prepare aluminum matrix composites (AMCs) reinforced with Al₂O₃ particles. Different mass fractions of micro alumina particles were injected into the melt under stirring speed of 300 r/min. Then the samples were extruded with ratios of 1.77 or 1.56. The microstructure observation showed that application of the injection and extrusion processes led to a uniform distribution of particles in the matrix. The density measurements showed that the porosity in the composites increased with increasing the mass fraction of Al₂O₃ and stirring speed and decreased by extrusion process. Hardness, yield and ultimate tensile strengths of the extruded composites increased with increasing the particle mass fraction to 7%, while for the composites without extrusion they increased with particle mass fraction to 5%.     

Processing,Microstructure and Mechanical Properties of Ti6Al4V Particles-Reinforced Mg Matrix Composites

Novel Ti6Al4V particles-reinforced AZ91 Mg matrix composites were successfully fabricated by stir casting method. The stirring time in semisolid condition directly affected the particle distribution and the quality of the ingots.Furthermore, the optimal speed of the heating and the liquid stirring could overcome particle settlement caused by the density difference between the matrix and the particles. Ti6Al4V particles distributed uniformly in the composites with different particle contents. The average grain size decreased with the increase in the particle contents. The Ti6Al4V particles bonded pretty well with the alloy matrix. In addition, there were some interfacial reactions in the composites.There were rod-like Al_3Ti phases at the interface. The precipitates extended from the particle surface to the matrix, and they might improve the interfacial bonding strength. The ultimate tensile strength, yield strength and elastic modulus were enhanced as the particle contents increased, and the elongation was much better than that of the same matrix material reinforced with SiC particles. Thus, the novel composites exhibit better comprehensive mechanical properties.     

碳纤维-FeCoCrNiAl高熵合金颗粒混杂增强7075铝基复合材料的力学性能及断裂行为

为探究双相增强体对铝基复合材料拉伸性能和断裂行为的影响,采用真空热压烧结工艺在580 ℃,30 MPa条件下保温10 min制备了FeCoCrNiAl高熵合金颗粒增强7075铝基复合材料（HEA_p/Al）,Ni-Co-P镀层修饰碳纤维增强7075铝基复合材料（CF/Al）和FeCoCrNiAl高熵合金颗粒及Ni-Co-P镀层修饰碳纤维混杂增强铝基复合材料（CF-HEA_p/Al）。并对不同复合材料微观结构及拉伸性能进行分析表征及比较。结果表明：CF-HEA_p/Al复合材料的屈服强度（YS）与极限拉伸强度（UTS）随纤维含量的升高（体积分数由0至40%）呈现先增大后降低的变化,延伸率则逐渐降低。鉴于Ni-Co-P镀层修饰碳纤维与FeCoNiCrAl高熵合金颗粒的混杂强化效应, CF-HEA_p/Al复合材料的YS和UTS较HEA_p/Al与CF/Al复合材料明显提高,且其断口表现出基体韧性断裂及纤维拔出与断裂的多种失效特征。     

Microstructures and mechanical properties of Al 2519 matrix composites reinforced with Ti-coated SiC particles

Ti-coated SiC_p particles were developed by vacuum evaporation with Ti to improve the interfacial bonding of SiC_p/Al composites. Ti-coated SiC particles and uncoated SiC particles reinforced Al 2519 matrix composites were prepared by hot pressing, hot extrusion and heat treatment. The influence of Ti coating on microstructure and mechanical properties of the composites was analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results show that the densely deposited Ti coating reacts with SiC particles to form TiC and Ti₅Si₃ phases at the interface. Ti-coated SiC particle reinforced composite exhibits uniformity and compactness compared to the composite reinforced with uncoated SiC particles. The microstructure, relative density and mechanical properties of the composite are significantly improved. When the volume fraction is 15%, the hardness, fracture strain and tensile strength of the SiC_p reinforced Al 2519 composite after Ti plating are optimized, which are HB 138.5, 4.02% and 455 MPa, respectively.     

复合铸造工艺参数对A356-SiC_p复合材料显微组织和拉伸性能的影响(英文)

研究复合铸造工艺参数对A356-SiCp复合材料显微组织和拉伸性能的影响。在590、600和610°C的温度条件下,分别以200、400和600 r/min的速度对样品进行半固态搅拌,搅拌时间分别为10、20和30 min。分析SiC颗粒在基体材料中的分布、样品的孔隙率和拉伸性能。结果表明,通过延长搅拌时间和降低搅拌温度,可以提升颗粒分布的均匀性;然而,随着搅拌速度的提高,颗粒分布的均匀性呈先上升后下降的趋势。同时还发现,通过增大所有的工艺参数,孔隙率得到了提高。从抗拉特性来看,最佳的搅拌速度、温度和时间分别为400 r/min、590°C和30 min。与孔隙率相比,增强相分布的均匀性对拉伸性能的影响更明显。     

In situ formation of various intermetallic particles in Al–Ti–X(Cu,Mg) systems during friction stir processing

In situ Al composites reinforced by various intermetallic particles were fabricated from Al–Ti–X(Cu, Mg) systems by hot pressing, forging and subsequent 4-pass friction stir processing (FSP). The formation of various intermetallic particles during FSP and the tensile properties of in situ composites were investigated. For Al–Ti–Cu system, Cu enhanced the Al–Ti reaction and resulted in the formation of more Al₃Ti particles due to the presence of a small amount of liquid phase during FSP. After FSP, part of Cu was kept in the Al matrix as solute, whereas the other formed Al₂Cu particles. For Al–Ti–Mg system, except for Al₃Ti, some Ti₂Mg₃Al₁₈ particles with fine twin lamellas were formed during FSP, resulting in an increase in the total volume fraction of reinforcing particles. Cu and Mg addition increased the strength of the in situ composites substantially due to introduction of more strengthening modes and more reinforcing particles, however the elongation decreased dramatically.     

Effect of ultrasonic vibration on microstructural evolution of the reinforcements and degassing of in situ TiB2p/Al-12Si-4Cu composites

Some issues such as clustering of TiB₂ particles, formation of long rod-like Al₃Ti particles, as well as high porosity level usually associate with the fabrication of in situ TiB_2p/Al-alloy composites via conventional stir casting technique using Ti and B as reactants. High-intensity ultrasonic vibration was introduced in our research to solve the above issues. The process involved that the original in situ TiB_2p/Al-12Si-4Cu sample with large clusters of TiB₂ particles, large long rod-like Al₃Ti particles and high porosity was remelted at 850 °C, and then ultrasonic vibration was applied to the melt with an ultrasonic probe. The microstructural evolution of the samples treated by ultrasonic vibration with different time was examined by using SEM. After treated by ultrasonic vibration for 12 min, large clusters of TiB₂ particles were broken up effectively and TiB₂ particles were dispersed uniformly in the matrix, and long rod-like Al₃Ti particles were turned into blocky ones with the size of 10 μm due to the effect of ultrasonic stirring. In the meantime, the porosity in the composites decreased from about 6.5% to 0.86% due to the effect of ultrasonic degassing. Microhardness test suggested that a homogeneous microstructure of the composite was achieved after ultrasonic treatment. An effective approach using high-intensity ultrasonic vibration to optimize the microstructures of the particulate reinforced Al-alloy composites was proposed, and the mechanism of the effect of high-intensity ultrasonic vibration on the microstructural evolution of the reinforcements and degassing of composites was also discussed in our research.     

球磨与烧结对Al2Ti3V2ZrB/2024Al复合材料组织与硬度的影响

利用粉末冶金方法制备了Al2Ti3V2ZrB/2024Al复合材料,研究了球磨工艺和烧结温度对复合材料微观组织和硬度的影响。结果表明,球磨时过高的球磨速度或过长的球磨时间均会造成Al2Ti3V2ZrB颗粒的团聚,影响复合材料的组织均匀性。在球磨速度为150r/min下球磨5h,Al2Ti3V2ZrB颗粒在2024Al基体中的分布最均匀,复合材料的硬度最高。当烧结温度低于510℃时,Al2Ti3V2ZrB颗粒在2024Al基体中分布比较均匀,复合材料密度和硬度随烧结温度升高逐渐增加;超过510℃后Al2Ti3V2ZrB颗粒开始团聚,复合材料密度和硬度下降,在510℃制备的复合材料具有最高的硬度。