Development of high strength aluminum alloy sheet by powder rolling-spark sintering technique using rapidly solidified powder

铝材料的烧结难度很大，因为它们对氧的亲和力很高，而且它们的烧结温度范围很窄。火花烧结的优点概括为：(1)氧化膜的介电击穿是在粉末颗粒表面之间引起的；(2)在较短的低温暴露条件下完成了烧结过程。为了开发高强度铝板，本文采用粉末轧制和电火花烧结相结合的金属板材制备工艺，对7075快速凝固铝粉进行了冷轧和电火花烧结。主要研究结果如下：1.在粉末轧制-电火花烧结过程中，辐射高温计(激光定向非接触式红外测温仪)只能测量材料的表面温度。然而，m…的内部温度在烧结过程中，更多的原料是重要的。在模压式火花烧结机上用热电偶测量了石墨冲头和压坯的真实温度。通过这些测量得到了材料表面温度与材料中心温度之间的关系。通过改变保温温度、烧结时间、冷却方式等工艺参数，获得了不同的显微组织。用透射电子显微镜和X射线衍射仪研究了其微观结构的变化。主要合金元素的固溶量随着保温温度的升高和保温时间的延长而增加，从而取代了均匀化处理和固溶处理。在873K下烧结10-2400秒的材料的时效硬化行为是相同的。另一方面，材料的塑性应变随着873K保温时间的延长而增加，873K烧结1200s的材料塑性应变与固溶处理材料的塑性应变相同。根据拉伸试验得到的塑性应变值，认为在长时间暴露和较高温度条件下烧结的材料具有大量的主要合金元素的固溶量和促进烧结的作用。针对电火花烧结工艺，对凝固分析计算机软件进行了改造。进行了包括电流、电压变化和发热过程在内的热分析。较少

The sintering of aluminum materials is difficult, since their affinity for oxygen is very high and their temperature range for sintering is very narrow. The advantage of spark sintering is summarized as follows : (1)The dielectric breakdown of the oxide film is caused between the powder particle surfaces, (2)The sintering process is finished under the condition of the shorter low temperature exposure. In order to develop the high strength aluminum sheet, the technique, (hereafter called powder rolling-spark sintering process), having both process of powder rolling and spark sintering for fabrication of metallic sheet is used for cold rolling and spark sintering of 7075-rapidly solidified aluminum powder in this study. The obtained results are summarized as follows :1. Only surface temperature of materials can be measured by radiation pyrometer (non-contact infrared thermometer with laser beam targeting) in the powder rolling-spark sintering process. However, the inner temperatures of m … More aterials is important in the sintering process. The real temperatures of graphite punches and compacts are measured by using of thermo couples in the die-press style spark sintering machine. The relation between temperature of materials-surface and one materials-center is obtained from these measurements.2. The various microstructures is obtained by changing of process parameters, such as holding temperature, period of sintering and cooling method. The microstructural changes is investigated using TEM and x-ray diffraction techniques. The solid soluted amount of main alloying elements increases as the holding temperature and period increase, which results in substitution of both homoginizing and solution heat treatments.3. The behavior of age-hardening is same for materials sintered at 873K for 10 to 2400 sec. On the other hand, plastic strain of material increases as the holding period in the sintering at 873K increases, and that of materials sintered at 873K for 1200sec is same as that of solution treated materials. It is suggested on the basis of value of the plastic strain obtained from tensile test that materials sintered under the conditions of the long exposure and higher temperatures show largely solid-soluted amount of main alloying elements and promotion of sintering.4. The computer soft for solidification analysis is modifed for spark sintering process. The thermal analysis including current-, voltage-change and heat generation process is carried out. Less