深冷处理对15%SiCp/2009铝基复合材料组织与力学性能的影响

采用硬度测试、X射线衍射物相分析、力学性能测试和透射电镜(TEM)观测等方式,研究长时间深冷处理对固溶-时效处理的碳化硅颗粒增强铝基复合材料组织与性能的影响,并从材料组织角度分析了深冷处理改善碳化硅颗粒增强铝基复合材料力学性能的机理。结果表明,与未经深冷处理的时效态铝基复合材料相比,经深冷处理的铝基复合材料试样提前2 h达到硬度峰值,约211.7 HV0.1,且整个时效阶段硬度均高于未深冷处理试样;时效早期(欠时效)阶段,经深冷时效处理的颗粒增强铝基复合材料试样组织中存在细小且均匀分布的针状析出相,而对比时效试样组织未见明显析出现象; 过时效阶段中,深冷-时效试样与时效试样均存在大尺寸析出相,且后者析出相尺寸、分布明显不均匀,但两者的力学性能随时效时间的延长而趋于近乎一致,说明深冷处理的影响降低。     

深冷时效循环处理铝基原位复合材料的显微组织和力学性能

采用熔体直接反应法,以工业7055铝合金为基体,利用K2TiF6和K2ZrF6多组元制备Al3(Ti0.5Zr0.5)原位颗粒强化铝基复合材料,再将复合材料经过挤压、固溶时效处理后进行深冷时效循环处理。采用正交实验设计法研究降温速度、处理时间和循环次数对复合材料显微组织和力学性能的影响。采用差示热分析仪对复合材料进行低温热分析,采用SEM和TEM对材料显微组织进行观察。结果表明:材料从液氮温度77 K升温至165 K左右时出现了明显的放热峰,此温度处出现了相变。热计算结果表明该温度下大量析出了S相(Al2CuMg)。深冷处理后复合材料内部细小析出相数量增多,主要组分是η(MgZn2)相和η′(MgZn2′)相;随着降温速度、处理时间和循环次数增加,性质不稳定且硬度高的η′相数量减少,性质稳定硬度较低的η相数量增加。与未冷处理试样相比,深冷时效循环处理后试样的平均抗拉强度提高14.7%,冲击韧性提高10.9%,伸长率提高50%,断裂机制为韧窝型断裂机制。当试样具有高强度、高韧性时,对应的最优冷处理参数为:降温速度v为1℃/min、保温时间t为24 h、循环次数N为1或2。当试样的伸长率最高时,对应的参数为:v为10℃/min、t为36 h、N为1。复合材料强化机制为析出相强化、位错强化和细晶强化等。     

高速钢循环深冷处理工艺及机理研究

采用正交试验法对W6Mo5Cr4V2高速钢循环深冷处理工艺进行了研究,分析了不同深冷工艺参数对力学性能的影响,并使用TEM观察了循环深冷处理前后的微观组织.结果表明,回火次数对力学性能影响最大.其次是深冷循环次数,最后是深冷时间.深冷处理后在马氏体孪晶带上有超细碳化物析出,多次循环深冷处理后.碳化物数量增加.与-次长时间深冷处理相比,在深冷时间足够的情况下,采用多次循环深冷处理工艺效果更好.     

冷热循环对颗粒增强铝基复合材料微屈服行为的影响

采用微屈服强度测试、透射电镜和高分辨透射电镜分析,对经过不同冷热循环工艺处理后的颗粒增强铝基复合材料的微屈服行为进行了研究。结果表明,冷热循环次数虽然对颗粒增强铝基复合材料微屈服行为的宏观规律没有本质的影响,但是仍然影响颗粒增强铝基复合材料的微屈服行为。对球形颗粒而言,小应变量下的微屈服强度随冷热循环次数的增加而增高;但对棱形颗粒而言,循环次数的影响较为复杂。研究还表明,冷热循环次数影响颗粒增强铝基复合材料微屈服行为的主要原因是其位错组态和残余应力在不同的循环次数下有明显的不同。     

搅拌铸造法制备SiCp／A356铝基复合材料的研究

利用搅拌铸造技术制备SiCp/A356铝基复合材料.通过金相观察(OM),扫描电镜(SEM)及力学性能测试对所制备的颗粒增强铝基复合材料的显微组织和力学性能进行了研究.结果表明,SiC增强颗粒较均匀地分布于基体中,SiC/Al界面处存在明显的Si溶质偏聚,复合材料的孔隙率为4.2%;与基体合金相比,SiC颗粒的加入提高了复合材料的硬度和屈服强度,抗拉强度及延伸率略有下降;断口分析表明,搅拌铸造SiCp/A356铝基复合材料主要的断裂机制为SiC/Al界面脱粘及基体合金的脆性断裂.     

深冷处理对Cu46 Zr46 Al8非晶复合材料组织与性能的影响

利用铜模吸铸法在一定冷却速度下成功制备了树枝晶均匀分布的Cu46Zr46Al8非晶复合材料,并对其进行深冷处理,研究了深冷处理对其组织和力学性能的影响.结果表明,深冷处理使Cu46Zr46Al8非晶复合材料中晶体相B2 CuZr相晶粒显著细化,CuZr相形貌也发生明显改变,由原先的树枝状变为板条状,经分析板条状相为B19' CuZr相.微观结构的改变促使复合材料的室温力学性能得到显著改善,深冷8 h后其显微硬度和压缩断裂强度提高幅度最大,分别提高了14.67%和34.63%.     

SiC含量对铝基复合材料显微结构和性能的影响

研究了不同质量分数Si C颗粒增强铝基复合材料的显微结构和力学性能,采用热压烧结和热挤压工艺成功制备出Si C颗粒增强铝基复合材料,通过相对致密度、XRD、FESEM和拉伸力学性能测试等手段,探究了不同质量分数的Si C颗粒和热挤压工艺对铝基复合材料显微结构、抗拉强度以及断裂方式的影响。     

循环深冷-热处理对镍基高温合金GH3030力学性能和组织的影响

将循环深冷-热处理工艺引入到GH3030高温合金中,研究了深冷处理次数对GH3030力学性能的影响。研究发现,通过多次深冷-热循环处理工艺处理与经过单次深冷处理相比,GH3030的硬度值随着深冷-热处理循环次数的增加而逐步变大并最终趋于稳定,该硬度值比单次深冷处理的稳定硬度提高30.06%,比原材料的硬度提高14.59%,而对材料的抗拉强度几乎没有影响。     

颗粒增强铝基复合材料搅拌摩擦加工的研究现状及展望

从增强相在铝基体中的分布均匀性、铝基体晶粒形状尺寸变化、添加颗粒对复合材料综合力学性能的影响等方面出发,详细介绍了目前搅拌摩擦加工技术在制备碳化硅(SiC)、氧化铝(Al_2O_3)和碳纳米管等颗粒增强铝基复合材料研究中取得的阶段性成果;总结了采用搅拌摩擦加工技术制备颗粒增强铝基复合材料工艺过程中亟待解决的共性问题,包括:颗粒含量的提高,颗粒添加方式的改进、增强相颗粒种类的扩展等。     

粉煤灰微珠增强铝基复合材料的断裂力学行为

对粉煤灰微珠增强铝基复合材料的力学性能进行了研究,并对其拉伸断口形貌进行了扫描电镜观察.研究结果表明,复合材料的抗拉强度高于纯铝,随着粉煤灰微珠加入量的增加,复合材料的抗拉强度不断增加,但塑性下降.复合材料的断口出现较明显的"河流花样" 和撕裂棱,断裂形态由塑性断裂向脆性断裂转化.     

高阻尼AA6061/SiCp/石墨复合材料的制备与性能

介绍采用粉末冶金法制备ＡＡ６０６１／ＳｉＣｐ／石墨混杂金属基复合材料的工艺过程,并对复合材料的力学和阻尼性能进行了初步探讨。粉末冶金法制备的ＡＡ６０６１／ＳｉＣｐ／石墨混杂金属基复合材料中增强增阻颗粒分布均匀,其体积分数可精确控制,加之制备温度低,可避免有害的界面反应。ＳｉＣ颗粒作为增强剂能够增加复合材料的刚度和强度,而石墨颗粒为增阻剂可以提高复合材料的阻尼特性。试验结果表明,能够应用粉末冶金法制     

N2在等离子弧原位焊接SiCp/Al基复合材料中的作用

以0．8mm钛片作为填充材料，采用纯氩和氮氩混合等离子气体对SiCp／Al基复合材料进行等离子弧原位焊接，分析加入的N2对焊缝成形、焊缝组织和性能的影响。结果表明，随氮气体积分数增大，焊缝熔深也相应增大：增加氮气还改善了熔池中的热循环状态和冶金反应，生成TiN、AlN等新的增强相，有效地抑制脆性相的生成，改善了焊接接头的性能。力学性能实验表明，采用Ar＋N2作为离子气进行焊接时，焊缝硬度和强度都有提高。当N2体积分数约占15％时，拉伸强度达到最大值233．5MPa。     

Al-Mg系自生纤维增强铝基复合材料组织与性能

为解决金属基复合材料中外加增强体与基体间异质界面对材料性能带来的不利影响，提出一种基于粉末冶金技术的原位复合新工艺，并制备出自生金属间化合物纤维增强铝基复合材料。研究结果表明，原位生成的金属间化合物纤维均匀分布在基体中，并平行于材料制备时的挤出方向；原位复合材料的增强效果明显，屈服强度比外加复合材料和基体分别高出28％和95．7％，断裂强度则相应提高了20．6％和88．5％；原位复合材料的强化机制主要是基体和增强体间界面结合良好，既能发挥基体的塑韧性，又能有效发挥自生增强体的强度优势，材料的断裂机制为自生纤维脆性断裂和劈裂。本研究同时表明，此方法工艺简单，成本低廉，且效率高，容易实现产业化。     

Development and characterization of liquid carbon fibre reinforced aluminium matrix composite

The progress and developments in materials technology have resulted in several new materials like metal–matrix composites (MMCs). On account of excellent physical, mechanical and development properties, MMCs are applied widely in aircraft and automobile technology. The present paper deals with the development of aluminium matrix composite reinforced with carbon preform having a volume fraction of 20–25% using squeeze casting infiltration process. Hardness, impact and tension test on the squeeze cast matrix and the composite was conducted to study the improvement in properties compare to that of matrix. Even though ultimate tensile strength of composite is found to be decreased, an increased Brinell hardness number and a four-fold improvement in toughness are noticed. Characterization of the materials done using optical and scanning electron microscope (SEM) revealed that the carbon fibers are evenly distributed in the matrix and the alloy is appeared to have smaller dendrite size. The lack of observed fibre pull-out on fracture and improved mechanical properties resulted due to the good wetting of the fibers by the liquid alloy.     

Analysis of Microstructures and Mechanical Properties of Particle Reinforced AlSi7Mg2 Matrix Composite Materials

The present study examined the microstructures and mechanical properties (tensile and impact strength, hardness) of selected metal matrix composite materials. SiCp reinforced AlSi7Mg2 matrix composites were produced using gravity and squeeze casting methods and subsequently T6 heat treated. Some of the squeeze casted composites were shaped by extrusion. The extrusion generated an equiaxed matrix structure and SiCp caused a homogeneous distribution. The quasi absence of porosity in the squeeze casted composites led to improved mechanical properties. Whereas an increase in the SiCp ratio resulted in an increase of the tensile strength, it led to a decrease of the impact strength values. The enhancement of the mechanical properties following an applied heat treatment was better for materials shaped by extrusion.     

聚碳硅烷原位自生增强钛基复合材料的组织及性能研究

以低氧氢化脱氢钛粉和陶瓷先驱体聚合物聚碳硅烷(PCS)为原料,通过粉末冶金工艺原位自生制备高强高塑钛基复合材料,探究了PCS的引入对钛基复合材料的控氧效果、烧结致密化过程、基体显微组织和力学性能的影响规律。研究表明：采用湿混包覆工艺可以将PCS包覆于Ti粉表面,有效控制材料制备过程中的氧增,其中制备的Ti-1.0 wt.% PCS复合材料的氧含量为0.21~0.24 wt.%,显著低于未经处理的CP-Ti样品(0.36~0.41 wt.%)。在烧结过程中,PCS受热分解并与Ti基体原位反应生成TiC颗粒,弥散分布在基体中,而Si元素则固溶于Ti基体。PCS的引入对Ti基体的性能具有明显的改善作用,经1200 °C/2 h烧结制备的Ti-1.0 wt.% PCS复合材料致密度达到98.4%,洛氏硬度为47.3 HRC,屈服强度为544 MPa,抗拉强度为650 MPa,延伸率为14.5%,其综合性能指标显著优于CP-Ti样品。     

A356-5SiCp和A356吸铸温度变化的对比分析

对体积分数为5％的SiC颗粒增强的A356复合材料和A356合金分别进行吸铸试验,测量熔体充型与凝固过程中铸件和铸型的温度,讨论了SiCp/A356复合材料与A356合金的铸件和铸型的温度变化规律.结果表明,SiCp的加入使SiCp/A356复合材料凝固前温度下降速度增大,凝固后的温度下降速度减小;同时由于潜热不同,SiCp/A356复合材料结晶温度低于A356合金.     

FRACTURE MODE AND PROCESS OF SiC_w B_4C_p/MB15 MAGNESIUM MATRIX COMPOSITE

ＦＲＡＣＴＵＲＥＭＯＤＥＡＮＤＰＲＯＣＥＳＳＯＦＳｉＣｗ＋Ｂ４Ｃｐ／ＭＢ１５ＭＡＧＮＥＳＩＵＭＭＡＴＲＩＸＣＯＭＰＯＳＩＴＥ①ＳｕＹｉｎｇ，ＺｈａｎｇＧｕｏｄｉｎｇ，ＷａｎｇＨｕｉｍｉｎ，ＺｈａｎｇＤｉ，ＱｉｎＪｉｎｉｎｇＳｔａｔｅＫｅｙＬａｂｏｆＭ...     

Effect of Heat Input on Mechanical and Metallurgical Properties of Friction Stir Welded AA6061-10% SiCp MMCs

Metal matrix composites (MMCs) reinforced with SiC particles combine the matrix properties with those of the ceramic reinforcement, leading to higher stiffness and superior thermal stability with respect to the corresponding unreinforced alloys. However, their wide application as structural material needs proper development of a suitable joining process. In this investigation, an attempt was made to study the effect of heat input on the evolution of microstructure in weld region of friction stir welded AA6061-10% SiCp MMCs. The tensile properties of the joints were evaluated and they are related with microstructure and heat input of the process. The microstructure characterization of the weld zone shows evidence of a substantial grain refinement of the aluminum matrix and fracturing of reinforcement particles due to dynamic recrystallization induced by the plastic deformation and frictional heating during welding.     

Enhanced Mechanical Properties of AA5083 Matrix Composite via Introducing Al0.5CoCrFeNi Particles and Cryorolling

High-entropy alloy particles (HEAPs) can markedly enhance the mechanical properties of metal matrix composites (MMCs). In this study, AA5083/Al_0.5CoCrFeNi HEAPs MMCs with different HEAPs contents (0, 1, and 3 wt%) were prepared via a stir-casting, and then these MMCs sheets were hot rolled (573 K) and cryorolled (77 K), respectively. The mechanical properties of the MMCs sheets were measured by tensile testing and microhardness test. Additionally, their microstructures were analyzed by scanning electron microscopy and transmission electron microscopy. Results revealed that the ultimate tensile strength (UTS) of the as-cast AA5083/Al_0.5CoCrFeNi HEAPs MMCs were improved from 203 to 257 MPa by adding 3 wt% HEAPs. And the mechanical properties of the MMCs sheets were improved after cryorolling. After cryorolling with 50% rolling reduction ratio, the MMCs with 1 wt% HEAPs had an UTS of 382 MPa, which was 1.9 times that of the MMCs before rolling. Finally, the strengthening mechanisms of HEAPs and cryorolling on the AA5083/HEAPs MMCs were discussed.