Amorphous alloys, also known as metallic glasses, exhibit a series of excellent properties not found in conventional crystalline alloys due to their long-range disorder and short-range order. Rail transportation, aerospace, automobile and ship, armor protection, precision instruments and other fields have broad application prospects. However, amorphous alloys in the metastable state need to be obtained at a relatively fast cooling rate, and the currently used copper mold casting method can only produce amorphous alloys having a smaller critical dimension. In addition, since bulk amorphous alloys have severe room temperature brittleness problems, they are difficult to machine at room temperature. Molds of complex shape components cannot be or are difficult to machine, resulting in difficulty in obtaining sophisticated amorphous alloy components, which is another bottleneck restricting the application of amorphous alloys. Therefore, how to break through the critical size constraints of amorphous alloys and the fabrication of complex components is the key to expanding their application in the field of laser pointer.
In recent years, the rapid development of laser pointer printing technology has provided an opportunity to solve the above problems. Laser 3D printing technology is a kind of rapid prototyping technology. Unlike traditional machining technology such as cutting, laser 3D printing technology is a kind of “additive manufacturing” technology based on digital model files. "Digital, short-cycle, low-cost advanced manufacturing technology. Since the laser 3D printing technology is a forming method of point-by-point discrete cladding deposition, the laser heating area of each point is small, and the heat of the molten pool can be rapidly diffused to the substrate, so that the cooling rate of the laser molten pool is much larger than that of the non-magnetic The critical cooling rate of the crystal alloy makes it possible to avoid crystallization during the condensation process, thereby obtaining an amorphous state, which makes it possible to prepare an amorphous alloy without size limitation. In addition, laser 3D printing is based on metal powder as a raw material. The high-energy laser beam is used to melt and accumulate metal powder layer by layer. The digital model is used to complete the “near-final forming” of fully dense, high-performance and complex metal parts in one step. The preparation of complex amorphous alloy structures provides an ideal means.
Therefore, in view of the current small size of amorphous alloys and the difficulty in preparing complex components, laser 3D printing technology is the most likely to solve the above problems and realize the large-scale application of amorphous alloys.
Recently, Associate Professor Lu Yunzhuo of Dalian Jiaotong University collaborated with researchers from Harbin Institute of Technology and the University of Birmingham in the United Kingdom to optimize the optimal process parameters by means of finite element simulation using coaxial powder feeding laser 3D printing technology. A large-sized Zr-based amorphous alloy having a content of more than 90%. More importantly, the formed amorphous alloy has a gradient structure along the printing direction, which provides a possibility for the amorphous alloy as a gradient material in the field of laser pointer function, and expands the use range of the amorphous alloy. It has been found that the gradient structure of the amorphous alloy is caused by different degrees of crystallization caused by different thermal history experienced by different printing layers during the coaxial powder feeding laser 3D printing process.
The researchers used the coaxial pointer laser printing technology to optimize the optimal process parameters by finite element simulation method, and successfully prepared Zr-based amorphous alloys with large size, high amorphous content and gradient structure. The research results not only provide a new method for preparing large-sized amorphous alloys with complex shapes, but also lay a foundation for promoting large-scale application of high-performance amorphous alloys in engineering and functional fields. The research results were funded by the National Natural Science Foundation of China (51671042, 51671043, 51401041) and the Key Laboratory of Liaoning Provincial Department of Education (LZ2015011).