Al-Mg alloy modified by Sc/Zr microalloying is used to realize the generation of high-performance aluminum alloy materials. It has many advantages, such as high specific strength, strong corrosion resistance, low hot crack sensitivity, high thermal stability, and good creep resistance, and is widely used in aerospace, rail transit, chemical engineering, and other fields. The additive manufacturing process can adjust and control the deposition process window. Although it can inhibit the generation of solidification defects to a certain extent and improve the metallurgical structure, it is still unable to achieve the preparation of high-strength, high-density, and high-performance aluminum alloy bulk deposition samples. Multi physical field assisted metal solidification has always been an important means to achieve traditional casting products to break dendrites, refine grains, and reduce workpiece defects, which has important reference significance for improving the microstructure and mechanical properties of additive manufacturing components. To achieve the preparation of high-strength and high-density Al-Mg-Sc-Zr alloy, we use the laser melting deposition (LMD) technology to prepare the bulk samples of this alloy under different process conditions.
The purpose of this study is to clarify the influence of different external field assisted processing conditions on the pore defect derivation behavior, tensile stress, and other mechanical properties during LMD. The heat transfer conditions in the deposition layer are controlled by air cooling (AC) and water cooling (WC) substrates. At the same time, the influence of ultrasonic vibration on the pore defect inhibition behavior and mechanical properties such as micro-hardness and strength of the samples is studied. In order to provide some process reference and data support for the preparation of large size, high-performance,and high-density aluminum alloy parts by LMD technology, and to break through the limitation of SLM technology forming cavity size, the effects of water-cooling conditions and ultrasonic vibration assistance on the microstructure, pore defect evolution, and mechanical properties of deposited samples are studied by means of the metallographic microscope, scanning electron microscope, micro-hardness test, and room-temperature tensile test.
Al-Mg-Sc-Zr alloy bulk samples were prepared by LMD technology under different external field conditions. The influence of air cooling, water cooling, and ultrasonic vibration assistance conditions on the microstructure, tensile, and other mechanical properties of the deposited samples was studied. It was clarified that grain refinement and the inhibition of pore defects were the key factors to improve the micro-hardness and tensile mechanical properties of the deposited samples. The conclusions are as follows: