Al-50Si复合材料的制备及组织性能研究
发布时间：2019-03-20 19:43
【摘要】：Al-Si复合材料因其优异物理和机械性能特点(受热膨胀低、工件质轻、比强度高和表面耐磨),在于航天结构件应用领域、电子类产品封装领域、精密仪器加工行业广泛使用,目前已成为材料界创新领域的一个重要投入点。该课题以颗粒增强材料强度理论作为实验研究基础,以Si颗粒和6061铝合金粉末为原料,采用冷压烧结法+热挤压、真空热压法制备了此复合材料。在材料测定相关技术(光学显微镜、SEM及XRD)下观察了材料内部微观形态并测试鉴定了物相。通过测定复合材料的性能指标(硬度、致密度、抗拉强度、膨胀系数等),根据实验数据系统研究了工艺参数(混粉方式、温度,压制力)在制备材料时对其微观结构和外在性能变化规律;尝试了不同粉体处理方法及改变烧结过程对坯料施加的参数并对其影响进行了深入研究,利用粉末冶金烧结原理分析了Al-Si复合材料的制备过程和机理,确定了材料制备工艺方法和详细参数。试验表明:采用球磨混料方式既能显著改善Al-Si混合粉末的几何特性和烧结工艺特性,烧结后的材料组织和物理机械性能得到明显提高。采用冷压烧结法制备的Al-50Si复合材料的热膨胀系数较低,达到9.8×10-6K-1;但其组织疏松(致密度为85.67%);其强度低和硬度差,坯料须受二次成型改善其组织。通过热挤压后,Al-50Si复合材料的物理机械性能明显提高:材料的抗拉强度提高54%,致密度提高了14%,硬度提高了25%,但膨胀系数却略微升高;同时,复合材料内部微观组织得到明显改善;增强体Si颗粒的偏聚明显减弱,弥散均匀分布在铝基体中;材料内部的孔洞和缺陷明显降低。采用真空热压法与经过热挤压处理后的Al-50Si复合材料相比,材料的力学性能虽略低于热挤压的复合材料,但生产工序简单并且避免了周期性鱼鳞裂纹和尾缩的缺陷,材料的利用率得到了大大的提高。真空热压烧结过程中,随着热压设备压力从2×107Pa到6×107Pa过程中,材料的性能稳步提升,当压力达到8×107Pa附近时,样品的物理、机械性能提升停止并呈下降趋势。由于增强相硅颗粒脆性强,压力过大是导致其断裂重要原因,伴随裂纹产生抗拉性能不断降低。硅颗粒含量从35%增加到50%时,密度和抗拉强度逐渐下降,但其热膨胀系数值从1.467×10-5K-1逐渐降到1.031×10-5K-1,材料的硬度值有所提高。最佳制备方法为混粉方式(球磨)+成型方式(真空下热压烧结),试验确定的工艺参数为:烧结温度为565℃,烧结压制压力6×107Pa和保温时间3.5h。
[Abstract]:Because of its excellent physical and mechanical properties (low thermal expansion, lightweight workpieces, high specific strength and surface wear resistance), Al-Si composites are located in the application field of aerospace structures, electronic product packaging, and so on. Precision instrument processing industry is widely used and has become an important input point in the field of material innovation. Based on the strength theory of particle reinforced materials and Si particles and 6061 aluminum alloy powder, the composites were prepared by hot extrusion by cold pressing and vacuum hot pressing. The microstructure and phase of the material were observed by optical microscope, SEM and XRD. By measuring the properties of the composites (hardness, density, tensile strength, expansion coefficient, etc.), the technological parameters (mixing method, temperature, etc.) were systematically studied according to the experimental data. (2) the change of microstructure and external properties of the material during the preparation of the material; The preparation process and mechanism of Al-Si composites were analyzed by means of powder metallurgy sintering principle, and the effects of different powder treatment methods and parameters on the sintering process were studied in detail. The preparation process and detailed parameters of the material were determined. The results show that the geometric and sintering characteristics of Al-Si powder can be improved by ball milling, and the microstructure and physical and mechanical properties of sintered powder can be improved obviously. The thermal expansion coefficient of Al-50Si composites prepared by cold pressing sintering is low, which reaches 9.8 脳 10 ~ (- 6) K ~ (- 1), but its microstructure is loose (density is 85.67%), its strength is low and hardness is poor, the structure of billet must be improved by secondary molding. After hot extrusion, the mechanical properties of Al-50Si composites were improved obviously: tensile strength increased 54%, density increased 14%, hardness increased 25%, but expansion coefficient increased slightly. At the same time, the microstructure of the composites was improved obviously, the segregation of Si particles was obviously weakened and dispersed uniformly in the aluminum matrix, and the pores and defects in the composites decreased obviously. Compared with the Al-50Si composites treated by hot extrusion, the mechanical properties of the composites by vacuum hot pressing are slightly lower than those of the hot extruded composites, but the production process is simple and the defects of periodic fish scale cracks and tail shrinkage are avoided. The utilization rate of materials has been greatly improved. In vacuum hot pressing sintering process, with the pressure of hot pressing equipment from 2 脳 107Pa to 6 脳 107Pa, the properties of the materials increase steadily. When the pressure reaches 8 脳 107Pa, the physical and mechanical properties of the samples stop and decrease. Because of the strong brittleness and excessive pressure of the reinforced silicon particles, the fracture is very important, and the tensile properties of the reinforced silicon particles decrease continuously along with the cracks. When the content of silicon particles increases from 35% to 50%, the density and tensile strength decrease gradually, but the thermal expansion coefficient decreases from 1.467 脳 10-5K-1 to 1.031 脳 10-5K / 1, and the hardness of the material increases. The best preparation method is powder mixing (ball milling) (hot pressing sintering under vacuum). The experimental parameters are as follows: sintering temperature is 565 鈩，
本文编号：2444568
[Abstract]:Because of its excellent physical and mechanical properties (low thermal expansion, lightweight workpieces, high specific strength and surface wear resistance), Al-Si composites are located in the application field of aerospace structures, electronic product packaging, and so on. Precision instrument processing industry is widely used and has become an important input point in the field of material innovation. Based on the strength theory of particle reinforced materials and Si particles and 6061 aluminum alloy powder, the composites were prepared by hot extrusion by cold pressing and vacuum hot pressing. The microstructure and phase of the material were observed by optical microscope, SEM and XRD. By measuring the properties of the composites (hardness, density, tensile strength, expansion coefficient, etc.), the technological parameters (mixing method, temperature, etc.) were systematically studied according to the experimental data. (2) the change of microstructure and external properties of the material during the preparation of the material; The preparation process and mechanism of Al-Si composites were analyzed by means of powder metallurgy sintering principle, and the effects of different powder treatment methods and parameters on the sintering process were studied in detail. The preparation process and detailed parameters of the material were determined. The results show that the geometric and sintering characteristics of Al-Si powder can be improved by ball milling, and the microstructure and physical and mechanical properties of sintered powder can be improved obviously. The thermal expansion coefficient of Al-50Si composites prepared by cold pressing sintering is low, which reaches 9.8 脳 10 ~ (- 6) K ~ (- 1), but its microstructure is loose (density is 85.67%), its strength is low and hardness is poor, the structure of billet must be improved by secondary molding. After hot extrusion, the mechanical properties of Al-50Si composites were improved obviously: tensile strength increased 54%, density increased 14%, hardness increased 25%, but expansion coefficient increased slightly. At the same time, the microstructure of the composites was improved obviously, the segregation of Si particles was obviously weakened and dispersed uniformly in the aluminum matrix, and the pores and defects in the composites decreased obviously. Compared with the Al-50Si composites treated by hot extrusion, the mechanical properties of the composites by vacuum hot pressing are slightly lower than those of the hot extruded composites, but the production process is simple and the defects of periodic fish scale cracks and tail shrinkage are avoided. The utilization rate of materials has been greatly improved. In vacuum hot pressing sintering process, with the pressure of hot pressing equipment from 2 脳 107Pa to 6 脳 107Pa, the properties of the materials increase steadily. When the pressure reaches 8 脳 107Pa, the physical and mechanical properties of the samples stop and decrease. Because of the strong brittleness and excessive pressure of the reinforced silicon particles, the fracture is very important, and the tensile properties of the reinforced silicon particles decrease continuously along with the cracks. When the content of silicon particles increases from 35% to 50%, the density and tensile strength decrease gradually, but the thermal expansion coefficient decreases from 1.467 脳 10-5K-1 to 1.031 脳 10-5K / 1, and the hardness of the material increases. The best preparation method is powder mixing (ball milling) (hot pressing sintering under vacuum). The experimental parameters are as follows: sintering temperature is 565 鈩，
本文编号：2444568
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