Papers by Author: Zhi Yuan Li

Abstract: To figure out the elements distribution in the seams, laser welding was carried out on the Al plates which coating with Si powder and Cu powder respectively, then electronic probe was used to analyze the microstructure in the section of the seams. Results indicated that alloying elements distribution in the weld is heterogeneous under the metal liquid movement in welding pool and the elemental diffusion co-functioning. There are two high concentration regions on both sides of the weld centerline, the content at the center is low, slightly higher and more homogeneous at the bottom. The distribution of the alloy composition in the weld is related to the specific gravity of the alloying elements. Though the specific gravity of Si and aluminum matrix is similar, it can flow with the liquid metal in the pool, so the concentration changes of Si in the weld are larger. Elemental fluctuation keeps steady in the weld joint.

Abstract: Laser welding of 1A90 pure aluminum and ZL114A aluminum alloy with powder under the same laser welding parameters were carried out in this work. The relation between weld elements and solidification cracking formation of these two materials was investigated in the perspective of metallurgical factor. And the alloy element contents and distribution near the cracks were determined by scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS). Then the concept of weld element equivalent was introduced comparing with the carbon equivalent expression. The weld element equivalent expressions were established by using mathematics regress. And the verified results indicate that the weld element equivalent expressions can properly forecast the formation of solidification cracking.

Abstract: To analyze the feasibility about diffusion bonding of Ti-6Al-4V alloy (represented by TC4 below) and type 25 low carbon steel (represented by 25-steel below), two kinds of experiments have been conducted by Gleeble-1500. One is directly diffusion bonding research of TC4 and 25-steel, the other is diffusion bonding of TC4 and 25-steel with adding Ni intermediate layer. The surface microstructures and the phase composition of bonding Joint have been systematic analysis through scanning electron microscope (SEM), energy spectrometer and XRD. Results indicated that the Ni intermediate layer largely improve the strength of joints observably, by suppressing the harmful diffusion between two sorts of based metal to avoid the appearance of harmful intermetallics in the joints.