金属构件微尺度搓铸成型研究

As the representative of traditional additive manufacturing methods, casting is still one of the main machinery manufacturing methods to this day due to its advantages of high-efficiency and easy-normalization. But its application range is restricted by the forming accuracy and performance. As the representative of modern additive manufacturing methods，laser cladding can be used to fabricate a metal component by remelting powder and freeforming. To be treated by hot isostatic pressing, the performance of the component is comparable to the level of forging. But the range of application is limited by its high cost. Based on the above reasons, the project applicant proposes a new additive manufacturing method without mould base on microscale cast-rolling. The feasibility of this method has been verified by the experiments of a tin alloy. The working principle is as follows: the metal melt is extracted from the furnace directly, then makes it fill the unrestrained flat space with diameter of mm scale, thickness of micron scale under a certain pressure. The directional solidification occurs in the movement of cast-rolling. The required metal components can be manufactured to coat this solidification structure by point by point and layer by layer according to the specified paths and graphics. The project will take aluminum alloy as the research object, and researches the relationship between the roll-casting parameters and the surface quality and mechanical properties of the formed parts.

作为传统增材制造方法的代表，铸造因为流程短且规范性好，至今仍是机械制造的主要方法之一。但其应用范围受制于其成型能力和成型件的性能。作为现代增材制造方法的代表，激光熔覆通过重熔粉末无模成型金属构件,辅以热等静压处理，其性能可以比肩锻造水平。但高昂的成本限制了其应用范围。为此,本项目申请人提出了基于微尺度搓铸的无模增材制造新方法，并用锡合金验证了其技术可行性。其具体工作原理是：直接从熔炉引出熔体，将其填充到直径为毫米、厚度为微米尺度、四周无约束的扁平空间，使其在不断地搓动和剪切过程中定向凝固并获得细化组织，所需金属构件就是这种凝固组织按指定轨迹与图形逐点逐层堆积的结果。本项目拟以铝合金为对象，研究搓铸参数与成型件表面质量和力学性能的关系。

研制了恒液面高度（第二代）无模成型实验设备，并成功地实现了锡铅合金在毫米尺度下的搓铸无模成型。扫描电镜观察结果表明：成型件的组织细小、均匀，其界面可以冶金结合，进一步证实了“液态金属搓铸无模成型方法”的技术可行性。对显微组织进行的能谱分析结果表明：成型件材料中铅锡两种合金元素的比例与原料不同，由以锡为主的锡铅合金变成了以铅为主的铅锡合金。这显然是由于在熔化原料的过程中，较重的铅元素向坩埚底部沉积、而较轻的锡元素上浮，而成型样件取材于坩埚底部的液态金属所致。这一问题提醒我们：成型之前必须对液态合金采取搅拌措施。根据上述经验，我们设计并研制了以铝合金为对象、带有搅拌器的、可以实现小至百微米尺度的搓铸无模成型实验设备。目前，该设备已安装到位，明年一季度可完成调试和验收并开始铝合金无模成型实验。