ZL101/SiCp复合材料制备及其缺陷分析

对于高增强体含量的复合材料,其材料的致密性显得尤为重要,本文采用冷等静压结合热等静压的方式制备SiCp/Al复合材料克服了这个困难,实现净成形,具有工艺简单等优点,使用180#α-SiC颗粒作为增强体,体积分数为20%,同时采用ZL101铝粉作为基体,其中采用冷等静压方法能制备出冷坯料材料的理论密度可达75%,后续采用热等静压制备出的碳化硅颗粒增强铝基复合材料具有致密性良好,颗粒分布均匀,无明显的聚集现象。同时结合SEM和EDS对界面的分析表明碳化硅颗粒增强铝基复合材料产生的缺陷主要是增强体碳化硅颗粒和铝基体结合的界面处有细小的气孔存在,使材料的有效承载面积减小,最终导致材料破断。初步分析了复合材料微缺陷产生的机理。界面处反应生成的界面相对于复合材料的影响。     

Study on diffusion welding SiCp/ZL101 with Cu interlayer

Through the vacuum diffusion welding SiCp/ZL101 aluminum with Cu interlayer,the effect of welding parame-ter and the thickness of Cu on the welded joint property was investigated,and the optimal welding parameters were putforward at the same time.The microstructure of joint was analyzed by means of optical-microscope,scanning electron mi-croscope in order to study the relationship between the macro-properties of joint and the microstructure.The results showthat diffusion welding with Cu interlayer could be used for welding aluminum matrix composites SiCp/ZL101 successfully.     

固/液熔接CuW/ZL101A界面结合机理

采用固/液熔接法制备了CuW/ZL101A整体材料,并对CuW/ZL101A扩散溶解层组织结构与形成机制进行了研究。实验表明,当熔接条件为(690~705)℃/60 min可以获得良好的结合界面,其界面结合为扩散与溶解结合,界面扩散溶解层主要由平面状扩散溶解层、柱状方向性扩散溶解层、共晶扩散溶解层3部分组成,其生长方向均趋于沿界面法线方向生长,利用扫描电子显微镜和X射线衍射仪观察和分析了各扩散溶解层的新相组成。以705℃/60 min为例,分析了整体界面扩散溶解层组织结构演变和形成机理:平面状扩散溶解层和柱状方向性扩散层分别由铜钨界面原子沿CuW界面形核结晶横向生长连成整体形成小平面状扩散溶解层,再转向正常纵向生长所形成;共晶扩散溶解层是由接近及远离共晶成分点的铝铜形成层片状伪共晶及网状离异共晶组织;以熔接690℃保温不同时间对界面扩散溶解层的影响可知:随着熔接时间延长,界面扩散溶解层形貌相同,无新相层的形成,仅扩散厚度存在差异。     

TiB_2/ZL101复合材料与ZL101合金激光焊对比研究

对TiB_2/ZL101复合材料和ZL101基体合金进行激光焊对比研究,结果表明:TiB_2/ZL101复合材料对激光的吸收率大于ZL101基体合金,相同工艺参数焊接时复合材料的焊接深度大于基体合金。由于基体合金导热率较大,使得焊缝上部比复合材料焊缝较宽。在功率一定时,较快的焊接速度(3 m/min)使得基体合金焊缝组织为α相和分布在α相间的针列状共晶体复合组织;而在较慢的焊接速度(2 m/min)时,基体合金焊缝组织为α相和分布较均匀的块状或长针状共晶Si相。复合材料在较快的焊接速度(3 m/min)时,晶界壁较薄,仅有少量共晶Si存在,在较慢的焊接速度(2 m/min)时,晶界壁明显变厚,共晶Si相较多。通过测试两种不同焊接速度的ZL101合金焊缝硬度表明,焊缝硬度值均比母材高,但共晶Si以针状或块状存在的焊缝硬度值小于针列状形式存在的焊缝硬度值。     

Interface structure and formation mechanism of diffusion-bonded joints of TiAl-based alloy to titanium alloy

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高能超声波搅拌法制备SiCp/ZL101复合材料的研究

用浸渗法制备了SiCp／ZL101复合材料预制块，通过在预制块的稀释过程中施加高能超声波搅拌，获得了增强颗粒弥散均匀，基体合金组织细小的复合材料。实验结果表明，与机械搅拌法相比，高能超声波搅拌法可以显著改善增强颗粒与基体合金润湿性，使颗粒在基体中弥散分布，并可有效避免夹杂和气孔的产生，是一种制备SiCp／ZL101复合材料的理想方法。     

SiCp/ZL101A复合材料半固态振动扩散钎焊

采用振动辅助下半固态扩散钎焊成功地焊接了SiCp/ZL101A复合材料.在连接过程中,施加了两次低频振动.第一次施加振动进行焊接时,钎料被加热至固液态.在此时钎料的半固态特征的获得是振动焊接成功的关键.半固态钎料的获得,可使钎料在焊接中不易被挤出.并且半固态钎料也加剧了钎料对基体表面的摩擦作用,从而促进了基体表面的氧化膜的破碎.然而,在一次振动焊接后的焊缝中的气孔限制了接头强度的提高.随后施加520℃的第二次振动,促使焊缝中的气孔被排除.此时接头的抗剪强度提高到160MPa.     

SiC_p/ZL101A复合材料半固态振动钎焊气孔缺陷的产生及抑制

对SiC_p/ZL101A复合材料半固态振动钎焊中气孔的产生原因进行分析,并制定相应的工艺改进措施来抑制焊缝中气孔的产生。通过分析得出:由于半固态钎料的抗拉强度和断后伸长率都较小,当振幅较大时(A=450μm、f=30 Hz),在振动过程中钎料被从中撕裂开,导致空气进入到焊缝区域中而形成气孔。通过减小振幅、并增加频率(A=100 μm、f=60 Hz),保证所得到的振动加速度值达到16 m/s~2,这样既能完全抑制焊缝中气孔的产生,又能确保界面上氧化膜被彻底去除。     

Joining of SiCp/Al composites by insert powder layers

Mixed Al-Si, Al-Si-SiC and Al-Si-W powders were employed as insert layers to reactive diffusion bond SiCp/6063 MMC. The results show that SiCp/6063 MMC joints bonded by the insert layer of the mixed Al-Si powder have a dense joining layer with a typical hypoeutectic microstructure. Using mixed Al-Si-SiC powder as insert layer, SiCp/6063 MMC can be reactive diffusion bonded by a composite joint. Because of the SiC segregations, however, there are a number of porous zones in the joining layer, which results in the low shear strength of the joints, even lower than that of joints reactive diffusion bonded by the insert layer of mixed Al-Si powder. The W added into the insert layer of Al-Si-W nearly all reacts with Al to form intermetallic WAl12 during bonding. The reaction between the W and Al facilitates to form a dense joint of high quality, and the formed interrnetallic WAl12 has a reinforcing effect on the joints, which lead to the high shear strength of the joints. In general, under the condition of fixed bonding time （temperature）, the shear strengths of the joints increase as the bonding temperature （time） increases, but tend to a maximum at bonding temperature of 600℃ （time 90 min）.     

稀土La对ZL101A合金组织及性能的影响

在ZL101A合金中加入不同量La，研究了其微观／宏观组织和热处理后的性能。实验结果表明。在金属型铸造条件下，加入质量分数为0．6％左右的La对ZL101A合金具有最好的变质效果，共晶硅全部变为细小点状。稀土La的加入可将合金晶粒尺寸由未变质时的3mm细化到1mm。共晶硅变质以及晶粒细化主要是由于加入的La富集在共晶硅前沿，阻碍了共晶硅长大。合金抗拉强度和伸长率随着La的增加而提高，但La超过一定量后合金抗拉强度和伸长率均会有不同程度的降低。     

应变率和相对密度对泡沫SiCp/ZL104压缩性能的影响

对采用熔体发泡法制备的泡沫5%(体积分数,下同)SiCp/ZL104复合材料进行了准静态和动态压缩性能的测试和分析.结果表明:无论是动态下压缩还是准静态下压缩,泡沫5%SiCp/ZL104复合材料的应力-应变曲线都呈现出典型的3个阶段:线弹性段、平台段和致密段;屈服应力对应变率很敏感,使得应变率增加时,屈服应力增加,且有应变硬化现象发生;随着相对密度的增大,泡沫5%SiCp/ZL104复合材料的动态屈服应力和流动应力与准静态载荷相比显著增加.     

Interface microstructure and formation mechanism of diffusion-bonded joints of TiAl to steel 40Cr

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氧化态SiCp/5052Al复合材料的界面及热导性能

研究了SiC颗粒经不同氧化时间的氧化行为,采用无压渗透法制备了体积分数大于55%的SiCp/Al复合材料,分析了复合材料的微观组织与界面形貌,探讨了氧化及界面反应对复合材料热导性能的影响。结果表明:当SiC颗粒在1100℃氧化时,随着氧化时间的延长,其氧化增重及氧化层的厚度均增加,但氧化时间大于6 h时,其增加速率减缓;经氧化处理后,颗粒尖角明显钝化,所制备复合材料颗粒分布均匀,致密度比颗粒未氧化时要高;且氧化改变了复合材料的界面反应及结合,未经氧化颗粒表面出现了短棒状Al_4C_3,4 h氧化后颗粒表面形成了八面体MgAl_2O_4,6 h氧化后仍有残余的SiO_2;随氧化时间的延长,复合材料热导及界面热传导系数均呈先增大后减小的变化趋势,这与不同氧化时的实际界面状况密切相关。     

ZL101A熔模铸件气孔和夹渣的成因及防止办法

结合铸造厂的生产实际,研究了ZL101A在高温液态下的氧化机制.利用光学显微镜以及金相技术,分析了铸件内气孔和夹渣的显微组织彤貌,总结了缺陷产生的原因和防止方法.结果表明,采用铝液中通入氩气法可以有效防止铸件内气泡的产生;采用陶瓷过滤法可以有效防止铸件内夹渣的产生.     

Study on fracture behavior of SiCp/A356 composites

The fracture behavior of SiCp/A356 composite at room and high temperatures was studied.Under tensile stress condition at room temperature, the fracture is mostly a combination of the brittle fracture of SiC particles and ductile fracture of A356 matrix.As the tensile temperature increases, the composite changes the main fracture behavior to the separation fracture of the bonding surface between SiC particles and A356 matrix.When the tensile temperature reaches 573 K, the fracture behavior of the composites is almost the whole separation fracture of the bonding surface, which is the main strengthening mechanism at high temperature.Under the cycle stress condition at room and high temperatures, the main fracture behavior of the composites is always a combination of the brittle fracture of SiC particles and ductile fracture of A356 matrix.However, under the cycle stress at high temperature, cycle behavior of the composites changes from cycle hardening at room temperature to the cycle softening at high temperature.     

SiC颗粒和芯部材料厚度对泡沫SiCp/ZL104层合板弯曲性能的影响

用泡沫SiCp/ZL104复合材料作为芯部材料制备了泡沫SiCp/ZL104层合板,测试和分析了该类层合板的三点弯曲性能。结果发现,在相对密度相同的情况下,泡沫5%SiCp/ZL104(体积分数,下同)层合板的弯曲刚度随SiC粒度的减小以及芯部材料厚度的增加而增大;由于环氧树脂的填充,使得层合板刚度P/δ的实验值比计算值略高;SiC颗粒体积分数的增加致使泡沫SiCp/ZL104层合板的抗弯曲刚度增大;弯曲过程中的主要破坏模式是芯部剪切和局部凹陷,但随着芯部材料厚度的增加,层合板的破坏方式由芯部剪切向表面屈服和芯部凹陷过渡。     

TiAl/40Cr扩散连接接头的界面结构及相成长

在 1173～ 1373K、0 .3～ 5 .4ks的接合条件下对TiAl金属间化合物与 4 0Cr钢进行了真空扩散连接。采用扫描电镜 (SEM )、电子探针微区成分分析 (EPMA)、X射线衍射分析 (XRD)等方法确定了反应相的种类和界面结构。研究结果表明 ,在 1373K的接合温度下 ,TiAl/ 4 0Cr接头生成了TiC ,Ti3 Al,FeAl和FeAl2 4种反应相 ,形成了 3个反应层 ,界面结构为TiAl/Ti3 Al+FeAl+FeAl2 /TiC/脱碳层 / 4 0Cr钢。界面总反应层的厚度随接合温度和接合时间按抛物线方程成长 ,成长的活化能Q为 2 11.9kJ/mol,成长常数k0 为 4 .6× 10 -5m2 /s。当脆性反应层厚度为 3μm时 ,TiAl/ 4 0Cr钢接头的室温拉伸强度达到 183MPa的最大值。     

搅拌摩擦加工制备石墨烯/Al复合材料的界面微观结构

以纯净石墨烯为原料,采用搅拌摩擦加工法制备石墨烯/Al复合材料,主要通过透射电镜等手段观察分析复合材料石墨烯?Al的两种界面,即石墨烯平面?Al、石墨烯边缘?Al的界面微观结构,并对界面形成机制进行了分析。结果表明:石墨烯平面?Al界面清晰,是典型的机械结合界面;而石墨烯边缘?Al界面存在过渡,且在其附近偶尔还发现Al4C3的分布,此区域主要以扩散结合并可能具有部分反应(扩散+部分反应)的界面形式存在。复合材料的界面形成机制与石墨烯不同位置的C原子活性有关,平面内C原子的大π共轭结构使其高度惰性,形成机械结合界面;而搅拌摩擦加工过程对石墨烯的破坏主要发生在边缘,由于C—C键合被破坏,石墨烯边缘活泼的C原子与Al基通过C—Al原子的相互作用而形成扩散+部分反应的过渡界面。     

Numerical simulation on thixoforging of electronic packaging shell with SiCp/A356 composites

Based on the research of modern electronic packaging materials, thixo-forming technology was used to fabricate electronic packaging shell. The process of thixo-extrusion with SiC_p/A356 composites was simulated by the finite element software DEFORM-3D, then the flow velocity field, equivalent strain field and temperature field were analyzed. The electronic packaging shell was manufactured by extrusion according to the results from numerical simulation. The results show that thixo-forming technology can be used in producing electronic package shell with SiC_p/A356 composites, and high volume fraction of SiC_p with homogeneous distribution can be achieved, being in agreement with the requirements of electronic packaging materials.     

Finite element and experimental studies of the formation mechanism of edge defects during machining of SiCp/Al composites

In this paper, a multi-particle microfinite element model with a random particle distribution in SiCp/Al composites was developed using ABAQUS software. The formation mechanism of edge defects near the exit of orthogonal cutting was analyzed, and the effects of cutting parameters on the sizes of edge defects were investigated. The results indicate that both the brittle fracture of SiC particles and the plastic flow of Al matrix occur in the process of the edge defects formation. Additionally, the cutting speed has little effect on the sizes of edge defects but the cutting depth has a significant effect on the height and length of edge defects. The numerical results were also compared to the orthogonal cutting experimental data and found to be in reasonable agreement.