Effect of deformation temperature on the mechanical behavior and deformation mechanisms of Al-Al2O3 metal matrix composites

Aluminum-alumina (Al-Al₂O₃) metal matrix composite (MMC) materials were fabricated using the powder metallurgy (PM) techniques of hot pressing followed by hot extrusion. Different reinforcement weight fractions were used, that is, 0, 2.5, 5, and 10 wt% Al₂O₃. The effect of deformation temperature was investigated through hot tensile deformation conducted at different temperatures. The microstructures of the tested specimens were also investigated to characterize the operative softening mechanisms. The yield and tensile strength of the Al-Al₂O₃ were found to improve as a function of reinforcement weight fraction. With the exception of Al-10wt%Al₂O₃, the MMC showed better strength and behavior at high temperatures than the unreinforced matrix. The uniform deformation range was found to decrease for the same reinforcement weight fraction, as a function of temperature. For the same deformation temperature, it increases as a function of reinforcement weight fraction. Both dynamic recovery and dynamic recrystallization were found to be operative in Al-Al₂O₃ MMC as a function of deformation temperature. Dynamic recovery is dominant in the lower temperature range, while dynamic recrystallization is more dominant at the higher range. The increase in reinforcement weight fraction was found to lead to early nucleation of recrystallization. No direct relationship was established as far as the number of grains nucleated due to each reinforcement particle.     

Effects of temperature on fracture behavior of Al-based in-situ composites reinforced with Mg2Si and Si particles fabricated by centrifugal casting

An aluminum-based in-situ composites reinforced with Mg₂Si and Si particles were produced by centrifugal casting Al–20Si–5Mg alloy. The microstructure of the composites was examined, and the effects of temperature on fracture behavior of the composite were investigated. The results show that the average fraction of primary Si and Mg₂Si particles in the composites is as high as 38%, and ultimate tensile strengths (UTS) of the composites first increase then decrease with the increase of test temperature. Microstructures of broken specimens show that both the particle fracture and the interface debonding affect the fracture behavior of the composites, and the interface debonding becomes the dominant fracture mechanism with increasing test temperature. Comparative results indicate that rich particles in the composites and excellent interface strength play great roles in enhancing tensile property by preventing the movement of dislocations.     

电厂飞灰颗粒增强铝基复合材料的摩擦磨损行为

对挤压铸造制成的飞灰颗粒增强ZL109复合材料在不同条件下的的摩擦磨损行为进行了研究。结果表明：飞灰颗粒的加入可提高铝合金材料的耐磨性,复合材料同基体合金相比,摩擦因数也较低。在摩擦磨损过程中,在较低载荷下复合材料的摩擦表面形成一稳定的摩擦转移层,该转移层的存在可以起到降低摩擦因数的作用。在较高载荷下由于该摩擦转移层遭到破坏,从而影响了其减摩作用的发挥。镶嵌在基体中的飞灰颗粒在摩擦过程中主要起到承受载荷、限制对磨材料与铝基体直接接触的作用。脱落的飞灰颗粒可以起到“滚珠”的作用,在摩擦表面形成“三体”摩擦,从而起到减摩的作用。     

High strain rate superplasticity of SiC whisker reinforced pure aluminum composites

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热压烧结TZ3Y20A-SrSO4陶瓷基复合材料的高温摩擦学性能

采用化学沉淀法制备出粒径约80nm的等轴状SrSO4粉体。选用ZrO2(3mol%Y2O3)-20wt%Al2O3(TZ3Y20A)陶瓷为基体,采用热压烧结法制备出TZ3Y20A-SrSO4陶瓷基复合材料,并对复合材料的组织结构和力学性能进行了研究。采用球盘式高温摩擦磨损试验机测定复合材料从室温到800℃的摩擦学性能。TZ3Y20A-SrSO4复合材料在室温至800℃范围内摩擦系数在0.31～0.42之间,磨损率为10-5mm3/Nm数量级。加入SrSO4后复合材料的磨损表面形成了一层润滑膜,有效地改善了其高温摩擦磨损性能。     

Tribological stability of particle reinforced aluminum matrix composites in braking

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Microstructure and properties of mechanical alloying particles reinforced aluminum matrix composites prepared by semisolid stirring pouring method

Aluminum matrix composites reinforced with mechanical alloying particles(SiC_p) were fabricated by the semisolid stirring pouring method. The inf luence of mechanical alloying particles and Mg on the microstructure and mechanical properties of the composites was investigated by means of optical microscopy(OM), X-ray diffraction scanning(XRD), electron microscopy(SEM) and energy dispersive spectroscopy(EDS). Results show that the addition of Mg converts the agglomerate mechanical al oying particles in ZL101 matrix composites into dispersed distribution in ZL101-Mg matrix composites, large matrix grains into f ine equiaxed matrix grains, and eutectic phase into f ine particles. So the mechanical properties of ZL101-Mg matrix composites are better than those of ZL101 matrix composites. The mechanical properties of ZL101/ZL101-Mg matrix composites are gradually increased with the increase of the volume fraction of mechanical alloying particles. When the volume fraction of mechanical alloying particles is 3%, the Vickers hardness and ultimate tensile strength of the ZL101/ZL101-Mg matrix composites reach their maximum values.     

纯铜的高温变形行为

利用Gleeb le-1500热力模拟试验机,在温度为650-950℃、应变速率为0.01-5 s-1、总应变量0.7的条件下,对纯Cu高温塑性变形过程中的动态再结晶行为进行了研究和分析。试验结果表明：纯铜高温流动应力-应变曲线主要以动态回复和动态再结晶软化机制为特征,峰值应力随变形温度的降低或应变速率的升高而增加;在真应力-应变曲线基础上,建立的纯铜高温变形本构方程较好地表征了其高温流变特性。     

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。     

High temperature deformation behavior and microstructure evolution of wrought nickel-based superalloy GH4037 in solid and semi-solid states

Cylindrical samples of Ni-based GH4037 alloy were compressed at solid temperatures (1200, 1250 and 1300 °C) and semi-solid temperatures (1340, 1350, 1360, 1370 and 1380 °C) with different strain rates of 0.01, 0.1 and 1 s⁻¹. High temperature deformation behavior and microstructure evolution of GH4037 alloy were investigated. The results indicated that flow stress decreased rapidly at semi-solid temperatures compared to that at solid temperatures. Besides, the flow stress continued to increase after reaching the initial peak stress at semi-solid temperatures when the strain rate was 1 s⁻¹. With increasing the deformation temperature, the size of initial solid grains and recrystallized grains increased. At semi-solid temperatures, the grains were equiaxed, and liquid phase existed at the grain boundaries and inside the grains. Discontinuous dynamic recrystallization (DDRX) characterized by grain boundary bulging was the main nucleation mechanism for GH4037 alloy.     

Tailoring microstructure and mechanical properties of aluminum matrix composites reinforced with novel Al/CuFe multi-layered core-shell particles

Aluminum matrix composites (AMCs), reinforced with novel pre-synthesized Al/CuFe multi-layered core- shell particles, were fabricated by different consolidation techniques to investigate their effect on microstructure and mechanical properties. To synthesize multi-layered Al/CuFe core-shell particles, Cu and Fe layers were deposited on Al powder particles by galvanic replacement and electroless plating method, respectively. The core-shell powder and sintered compacts were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDX), pycnometer, microhardness and compression tests. The results revealed that a higher extent of interfacial reactions, due to the transformation of the deposited layer into intermetallic phases in spark plasma sintered composite, resulted in high relative density (99.26%), microhardness (165 HV_0.3) and strength (572 MPa). Further, the presence of un-transformed Cu in the shell structure of hot-pressed composite resulted in the highest fracture strain (20.4%). The obtained results provide stronger implications for tailoring the microstructure of AMCs through selecting appropriate sintering paths to control mechanical properties.     

High temperature DSC study on interfacial reaction of aluminum borate whisker reinforced aluminum alloys

1lNTR0DUCTIONRecently,theceramicwhiskerreinfOrcedmetalshavebeenpaidmoreattentionbecausethesecompositesp0ssessexcellentbehaviorssuchaslowdensity,goodstrength,highspecificstiffnessandspecificmodulus,exce1lentfatigue-resistanceandwear-resistance,andthenwhisker/metalcompositesbecomeanimportantbranchofmetalmatrixcomposites.TheearlydevelopedwhiskerreinforcedmetalaremainlyexpensiveSiCandSi3N4seriescomp0sites,sothatthewideapplicationsofthiskindofcompos-itesarelimited.Atpresent,astateofartwhisker…     

Improving tribological behavior of friction stir processed A413/SiCp surface composite using MoS2 lubricant particles

The effect of MoS₂ lubricant particles on the microstructure, microhardness and tribological behavior of A413/SiC_p surface composite, fabricated via friction stir processing (FSP), was studied. For this purpose, the FSP was carried out with tool rotational speed of 1600 r/min, tool travel speed of 25 mm/min and tool tilt angle of 3° through only a “single pass”. The optical and scanning electron microscopies, microhardness and reciprocating wear tests were used to characterize the samples. The results showed that the addition of MoS₂ lubricant particles to A413/SiC_p surface composite leads to the decrease of friction coefficient and mass loss. In fact, the generation of mechanically mixed layer (MML) containing MoS₂ lubricant particles in A413/SiC_p/MoS_2p surface hybrid composite results in the reduction of metal-to-metal contact and subsequently leads to the improvement of tribological behavior.     

WS2增强CoCrTi复合材料的制备及高温摩擦学性能

采用热压烧结技术制备了CoCrTi-(2.5, 4.0, 6.0)WS₂复合材料,并优化了WS₂的含量。通过球-盘式高温摩擦试验机研究了复合材料在室温至1000 ℃范围内的摩擦学性能。使用X射线衍射仪和扫描电镜等分析了复合材料的显微组织和物相组成。结果表明:适量WS₂的添加显著提高了材料的硬度与摩擦学性能。3种复合材料的摩擦因数和磨损率均表现出大致相同的变化趋势:在室温至400 ℃的试验条件下,摩擦因数随温度的升高而降低,磨损率变化趋势则相反。在400 ℃到1000 ℃,摩擦因数随温度的升高小幅增大;磨损率随温度的升高先减小后增大最后减小,在800 ℃时达到最大值。在给定的试验条件下,WS₂含量为4.0wt%的复合材料具有最佳的高温摩擦学性能。在低温下试样表现出不同程度的磨粒磨损,在高温下的磨损机理为氧化磨损。     

激光焊接颗粒增强铝基复合材料中TiB2颗粒的演变行为（英文）

研究大功率激光器焊接TiB2颗粒增强铝基复合材料时TiB2粒子的演变行为。采用X射线衍射(XRD)、扫描电镜(SEM)及能谱(EDS)分析焊缝内粒子的物相、热力学过程及形貌特征;同时对TiB2和铝基体的界面反应进行讨论。结果表明:当TiB2团簇尺寸大于激光光斑直径时,焊缝中部的TiB2粒子会熔融在一起,较大尺寸的TiB2会发生断裂;当与铝熔体接触后,熔化后的TiB2粒子会与Al发生反应生成Al3Ti和AlB12,并且焊缝中部的界面反应比焊缝边缘的剧烈。     

掺钨类金刚石膜离子渗硫后的微观结构与摩擦学性能

探讨了掺钨类金刚石(W-DLC)膜沉积及离子渗硫两步合成DLC和WS2复合固体润滑膜的新方法。利用低温离子渗硫技术对4种钨含量的W-DLC膜进行离子渗硫处理,采用扫描电子显微镜(SEM)、俄歇扫描探针(SAM)、X射线光电子能谱(XPS)、拉曼光谱仪(Raman),纳米硬度计(Nano-indenter)和摩擦磨损试验机考察了渗硫处理后W-DLC膜的微观结构与摩擦学性能。结果表明:渗硫处理使W-DLC膜中生成了WS2,促进了DLC膜的石墨化,并降低了其纳米硬度;随钨含量增加,渗硫处理的W-DLC膜纳米硬度逐渐升高,摩擦系数和磨损率逐渐减小,渗硫后的27.7%W-DLC膜表现出最优异的摩擦学性能。     

玄武岩颗粒增强7A04铝基复合材料的界面结构及力学行为

采用喷射成形技术制备7A04铝合金及玄武岩颗粒增强7A04铝合金复合材料,利用金相显微镜(OM)、透射电镜(TEM)、扫描电镜(SEM)和能谱(EDS)分析复合材料微观组织和界面结构,对比研究复合材料的力学性能。结果表明:玄武岩颗粒在铝基体中弥散分布,并与铝基体形成强力结合界面,玄武岩颗粒边缘的SiO₂不断被反应生成的Al₂O₃取代,形成一层几十纳米厚度的高温反应层,反应生成的Al₂O₃强化玄武岩颗粒与铝基体的结合界面;弥散分布的玄武岩颗粒促进基体中位错增殖、空位形成和析出相的析出,析出相主要以板状的η(MgZn₂)相和亮白色条状或椭球状的T(Al₂Mg₃Zn₃)相为主,结合界面、高位错密度及弥散分布的第二相显著提高复合材料的力学性能,添加玄武岩颗粒的7A04铝合金复合材料的屈服强度和极限拉伸强度分别达667 MPa和696 MPa,与未添加玄武岩颗粒的7A04铝合金相比分别提高10.4%和...     

Deformation behavior of SiC particle reinforced Al matrix composites based on EMA model

Effects of the matrix properties,particle size distribution and interfacial matrix failure on the elastoplastic deformationbehavior in Al matrix composites reinforced by SiC particles with an average size of 5μm and volume fraction of 12%werequantitatively calculated by using the expanded effective assumption(EMA)model.The particle size distribution naturally bringsabout the variation of matrix properties and the interfacial matrix failure due to the presence of SiC particles.The theoretical resultscoincide well with those of the experiment.The current research indicates that the load transfer between matrix and reinforcements,grain refinement in matrix,and enhanced dislocation density originated from the thermal mismatch between SiC particles and Almatrix increase the flow stress of the composites,but the interfacial matrix failure is opposite.It also proves that the load transfer,grain refinement and dislocation strengthening are the main strengthening mechanisms,and the interfacial matrix failure and ductilefracture of matrix are the dominating fracture modes in the composites.The mechanical properties of the composites strongly dependon the metal matrix.     

低温环境下2519A铝合金动态力学性能及组织演化

为研究低温下动态冲击对2519A铝合金流变应力和组织演化的影响,在低温下利用霍普金森压杆对2519A-T87态铝合金进行应变速率为1000~4200 s-1的动态冲击压缩实验,同时运用光学显微镜与透射电镜,对低温下的冲击微观组织进行观察和分析。结果表明:在低温环境下,绝热剪切带中心区域为亚晶组织,再结晶程度较低;同时,在形变带内出现长度较短、连续性较差的微裂纹,裂纹末端向基体扩展。随着冲击温度的降低,材料的屈服抗力迅速增加,出现绝热剪切带的临界应变速率随之降低。在中高应变速率下,长条状弥散相粒子发生不同程度的脆性断裂,从而引起流变应力的迅速提高。     

三维网络陶瓷增强铝基复合材料的干摩擦磨损性能

设计和制备了一种新型的三维网络陶瓷(骨架)增强铝合金复合材料.研究了铝合金及不同成分复合材料在不同温度及载荷下的摩擦系数和磨损率;用扫描电镜(SEM)观察其磨损表面,并分析了三维网络陶瓷(骨架)对铝合金磨损机制的影响.结果表明:复合材料的耐磨性远优于铝合金,而且随着三维网络陶瓷体积分数、温度及载荷的增加,复合材料的抗磨损性能明显提高;这种新型复合材料的摩擦系数随载荷变化保持稳定;在很宽的温度范围内,摩擦系数的稳定性均优于铝合金.这是由于三维网络陶瓷在磨损表面形成硬的微凸体起承载作用,其独特的结构制约了基体合金的塑性变形和高温软化,有利于磨损表面氧化膜的留存.