科研之友
微信
新浪微博
Facebook
分享链接
摘要
Objective: Owing to the excellent strength-to-weight ratio, SiC particle reinforced aluminum composites have been widely used in the aerospace industry. To maintain the structural performance, the welded joint strength must be maintained. It has been a challenge for SiC particle reinforced aluminum composites to keep the weld strength as base materials due to the SiC particle dissolution and chemical reaction between SiC particles and base aluminum alloys during the welding process. In the past, the common approach to join SiC particle reinforced aluminum composites is arc welding or single laser beam welding or the corresponding parameters' optimization. There are limited studies on various laser-welding approaches on weldability of SiC particle reinforced aluminum composites, and their microstructure and mechanical properties. In this study, we selected three laser-welding processes to join SiC/Al composite, which include 1) hybrid laser-CMT welding; 2) single laser beam welding with filler wire; 3) dual laser beam welding with filler wire. We obtained that using the dual laser beam welding process can significantly improve the weld surface quality. Single laser beam welding with filler wire can produce the highest tensile shear strength of about 69.4% of base SiC particle reinforced aluminum composite strength. The tensile shear strength is only 62.5% and 53.8% of the base material for hybrid laser-CMT welding and dual laser beam welding with filler wire, respectively. The reason for the degradation of the weld strength is attributed to the formation of a large amount of porosity in the weld fusion zone. Methods: Hybrid laser-CMT welding, single laser beam welding with filler wire, and dual laser beam welding with filler wire are used to join 4 mm SiC/Al composite with an ultimate strength of 318 MPa and volume fraction of 7.66% in a butt joint configuration. Tensile shear and micro-hardness tests are employed to evaluate the weld mechanical properties. The microstructures of the fractured weld are analyzed using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS). Besides, a digital microscope (KEYENCE: VHX-6000) is used to investigate the porosity distribution and ratio in various weld zones obtained using hybrid laser-CMT welding, single laser beam welding with filler wire, and dual laser beam welding with filler wire. X-ray powder diffraction (XRD) is used to identify the phase in the weld zone. Results and Discussions: Hybrid laser-CMT welding and single laser beam welding processes produced a rough weld surface in 4 mm SiC particle reinforced aluminum alloy (SiCp/Al) composite. The weld surface quality is significantly improved (Fig. 3) using a dual laser beam welding process. The tensile shear test showed that the single laser beam welding process produced the highest weld strength, which reached 69.4% of the base material. The hybrid laser-CMT welding and dual laser beam welding processes produced the weld strength of 62.5% and 53.8% of the base material, respectively (Fig. 4). All welds failed in the mode of combining porosity with dimples (Fig. 6). The welds showed inhomogeneous hardness profiles with selected welding processes (Fig. 7) are due to variation in SiC particle distribution and porosity formation in the weld (Fig. 8). Using the XRD technique, we obtained that the SiC reinforcement particles chemically reacted with molten aluminum matrix, and the Al4C3 compound is produced in the fusion zone during the laser welding process (Fig. 10). The experimental results showed that under the selected welding parameters, the porosity is mainly concentrated on the top and bottom part of the fusion zone for hybrid laser-CMT welding (Fig. 11(a)). However, the center part of the fusion zone is occupied by a large amount of porosity for dual laser beam welding with filler wire (Fig.11(b)). Compared with hybrid laser-CMT welding and dual laser beam laser welding with filler wire, porosity is significantly reduced, and it is obtained through the entire weld depth (Fig.11(c)). To investigate the SiC particle sizes and their distribution after the laser welding process, it is essential to consider the image analysis approach to analyze the weld fusion zone. We obtained that the amount of SiC particle is reduced by dual laser beam welding with filler wire to the highest level among the three laser-welding processes (Fig. 13). This phenomenon could be explained due to higher heat input from the dual laser beam promoted the chemical reaction between SiC particle and molten aluminum matrix. Conclusions: In this study, hybrid laser-CMT welding, single laser beam welding with filler wire, and dual beam laser welding with filler wire are selected to investigate the weldability of 4 mm SiC particle reinforced aluminum composite. The experimental results showed that uneven surfaces are usually found in the welds, which are achieved by hybrid laser-CMT welding and single laser beam welding with filler wire. The weld surface quality is significantly improved using the dual laser beam welding process. Under the selected welding parameters, the highest tensile shear strength of 208.2 MPa is obtained by single laser beam welding with filler wire, which is 69.4% of the base material. Besides, a large amount of porosity is found in the fusion zone, and their distribution is different. SiC reinforced particle is dissolved and segregated during laser welding process. The reduced SiC particle amount, porosity formation, and brittle Al4C3 formation in the fusion zone are the main reasons for the degradation of weld strength.
- 出版日期2021
- 单位中国科学院大学
