After welding, the metallurgical samples were prepared by
standard metallographic procedures and etched by a solution containing
4.2 g picric acid, 10 ml acetic acid, 10 ml water and 100 ml
ethanol with an etching time of about 20 s. The microstructure
and fracture surface were analyzed by optical and scanning electron
microscopy (SEM), respectively. The tensile samples were
prepared according to the drawing shown in Fig. 2 and tested
at room temperature. The result was the average value of three
samples.