液固分离法近净成形SiC_p/Al电子封装壳体的组织和性能(英文)

采用液固分离工艺制备高SiC体积分数Al基电子封装壳体(54%SiC,体积分数),借助光学显微镜和扫描电镜分析壳体复合材料中SiC的形态分布及其断口形貌,并测定其物理性能和力学性能。结果表明:SiCp/Al壳体复合材料中Al基体相互连接构成网状,SiC颗粒均匀镶嵌分布于Al基体中。复合材料的密度为2.93 g/cm3,致密度为98.7%,热导率为175 W/(m·K),热膨胀系数为10.3×10-6K-1(25~400°C),抗压强度为496 MPa,抗弯强度为404.5 MPa。复合材料的主要断裂方式为SiC颗粒的脆性断裂同时伴随着Al基体的韧性断裂,其热导率高于Si/Al合金的,热膨胀系数与芯片材料的相匹配。     

Effects of ac arc ultrasonic on plasma arc in situ welding of SiCp/6061Al MMCs

Abstract

The isolation coupling device is designed based on the principle of high pass filter circuit, which can achieve isolation and coupling between ac welding power and ultrasonic frequency excitation source. In addition, ac arc ultrasonic vibration is obtained successfully. The plasma arc in situ welding of SiCp/6061Al was performed using two different processes. The first process is that the plasma gas is argon nitrogen mixture and the filler material is flux cored wire (Al–5Ti–5Si); the other process is that the plasma gas is argon and the filler material is flux cored wire (Al–15Ti–3Si). The two joints are respectively enhanced by nitride and Al₃Ti, which were obtained in these processes. After arc ultrasonic vibrations were imposed on the two welding processes, it was revealed that arc ultrasonic improved the distribution of the new nitride phases and optimised the morphology of Al₃Ti to improve the mechanical properties of joints that reached 246 and 263 MPa. Fracture analysis showed that the improvement of the mechanical properties resulting from Al₃Ti is better than that from nitride under the effect of arc ultrasonic.     

超声振动磨削放电复合加工SiCp／Al试验研究

针对SiCp／Al的加工,提出一种超声振动磨削放电复合加工的方法．从加工效率、加工稳定性及表面质量等方面与电火花加工进行了对比试验研究。分析了两种加工方法的脉冲宽度和峰值电流对加工速度和表面粗糙度的影响,结果表明：电火花加工的表面粗糙度平均值为尺04．5μm,超声振动磨削放电复合加工的表面粗糙度平均值为Ra2μm：超声振动磨削放电复合加工的稳定性比电火花加工好,但加工速度较低。通过扫描电镜对两种加工方法下零件表面形貌和重熔层进行了观测,对试件表面进行了X射线衍射分析,表明采用超声振动磨削放电复合加工SiCp／Al复合材料可获得较好的表面质量。     

Optimisation of the spark plasma sintering process for high volume fraction SiCp/Al composites by orthogonal experimental design

Based on orthogonal experimental design (OED), the effects of the sintering pressure, sintering temperature and holding time on the mechanical properties of 50 vol% silicon carbide particle (SiCp)/2024Al composites prepared by spark plasma sintering (SPS) were investigated. The sintering pressure had the greatest effect on the density and bending strength of the material among these three factors, followed by sintering temperature and holding time. The optimised process conditions for producing the 50 vol% SiCp/2024Al were sintering at 550 °C for 5 min under 40 MPa, which resulted in a composite material with a density of 99.7% and good interface bonding with a comparatively high bending strength of 766.65 MPa. This work provides a promising method to produce high volume fraction composites that can meet high strength requirements.     

SiC_p／Al复合材料的抵抗温度变化尺寸稳定性

采用无压渗透法制备SiCp/Al复合材料,以温度单程变化时热膨胀系数(CTE),累积残余应变(εcr)为指标,研究复合材料在抵抗温度变化时的尺寸稳定性。结果表明,复合材料的热膨胀系数明显低于未增强铝基体,适当的预处理可显著提高其尺寸稳定性,适当的合金元素可提高颗粒增强铝基复合材料抵抗温度变化尺寸稳定性,随热循环次数增加,复合材料的εcr和CET稳定性趋向平稳。     

高体积分数SiCp/Al复合材料的热物理性能

采用无压渗透法制备了高体积分数SiCp/Al复合材料,用XRD对复合材料的物相进行了分析,测定了SiCp/Al复合材料在25～200℃温度区间的热膨胀系数及热导率,运用理论模型对复合材料的热膨胀系数以及热导率进行了计算,并探讨了热物理性能与温度之间的关系。结果表明,高体积分数SiCp/Al复合材料具有较低的热膨胀系数、高的热导率,综合热物理性能优良。     

CVI法制备SiCp/SiC复合材料的氧化性能研究

对用CVI法制备的SiCp/SiC复合材料的氧化性能进行了研究。材料含有的气孔和破坏氧化膜连续性的杂质元素,为氧气扩散提供通道;氧化过程中形成的气孔,导致了新的自由表面的暴露和空气扩散通道,进而加剧氧化。在材料的高温氧化过程中,SiC的氧化生成SiO2膜导致试样质量增加,玻璃碳界面层的氧化生成CO的逸出导致试样质量损失。最后的质量变化是这两种综合作用的结果。在高温氧化过程中,材料的空隙增多,应力集中加强,界面层被破坏使SiCp/SiC复合材料的强度下降。     

SiC颗粒增强Al基复合材料的热膨胀性能

采用气压浸渗方法制备了SiCp/Al(SiC颗粒增强铝基复合材料),由于浸渗程度的不同导致了复合材料密度的不同,研究了复合材料的工程CTE和物理CTE随密度的变化关系.实验结果表明,对于给定的SiC颗粒增强Al基复合材料,随着密度的增加工程CTE会出现3个不同斜率近似线性的增长,同时密度的增加会导致工程CTE下降,物理CTE突变点的温度升高,但是物理CTE突变点的值却不受密度的影响.     

不同应力比下SiCp/Al复合材料疲劳裂纹扩展行为

为了研究应力比对SiC颗粒增强铝基复合材料疲劳性能的影响,采用真空液态搅拌法制备了SiCp/Al复合材料,并对CT试样循环加载测定其裂纹扩展曲线.研究了三种不同应力比下的裂纹扩展行为,结果表明:随着应力比R增大,疲劳裂纹扩展速率da/dN降低.疲劳裂纹的断口形貌塑性断裂越明显,裂纹尖端塑性区增大,裂纹尖端钝化越显著,二次裂纹数量增加.