Search

Laser direct joining of carbon fiber-reinforced thermoplastic composites (CFRTP) to aluminum alloy with diverse surface micro-patterns was performed. The influence of micro-pattern type on interface characteristic and mechanical property of CFRTP/aluminum alloy laser bonding joint was concerned especially. Prior to the laser joining, two different micro-patterns including groove structure and circular hole structure were fabricated on the metal surface using nanosecond pulsed laser. Then, the appearance of joint and the morphology at joining interface were observed by optical microscope and scanning electron microscope. Moreover, the tensile shear test was conducted to obtain the fracture load and fracture surface morphology. The results indicated that the cross section of the groove structure was a trapezoid, while that of the circular hole structure was a triangle with a large ratio of depth to diameter. In spite of the more pores existed at the interface of joints with circular hole structure, this type of micro-pattern strengthened the mechanical anchoring effect between CFRTP and aluminum alloy more significantly. With the change of micro-pattern from groove structure to circular hole structure, the maximum tensile load of laser bonding joint increased from 1616.40 to 2623.40 N, and the main failure mode transformed from interface failure to cohesive failure. The micro-pattern fabricated on the metal surface before the laser joining process is an effective approach to obtain the larger bonding area and higher mechanical strength of laser bonding joint. [ABSTRACT FROM AUTHOR]

As the material experiences non-uniform thermal expansion and contraction under different thermal behavior during laser melting deposition (LMD), the microstructure of the components will be affected, which also causes changes in mechanical properties. It is essential to understand the thermal behavior of the melt pool during LMD to improve the microstructure and joint quality. In this study, two 80-mm-thick Ti6Al4V plates are successfully joined using three different scanning speeds (10, 15, and 20 mm/s). The effects of thermal behavior on the grain morphology and dimension of deposition area, equiaxed crystal zone (EQZ), and the substrate at different scanning speeds are quantitatively analyzed. The results show that the fine equiaxed crystals are formed near the joint boundary due to the high-temperature gradient and cooling rate. The growth direction of fine columnar crystals continuously changes from the joint boundary to the center of the deposition area due to the change of heat-extraction direction. However, the epitaxial growth direction of the coarse columnar crystal is the same as the previous deposition layer at the center of the deposition area. Given the effect of high heat accumulation and low-temperature gradient during LMD, the dimension of columnar crystal is coarsen significantly at the center of the deposition area. [ABSTRACT FROM AUTHOR]