Microstructure and Tensile Behavior of Laser Arc Hybrid Welded Dissimilar Al and Ti Alloys.

Ming Gao,Yunze Gu,Xiaoyan Zeng,Cong Chen

doi:10.3390/ma7031590

Abstract

Fiber laser-cold metal transfer arc hybrid welding was developed to welding-braze dissimilar Al and Ti alloys in butt configuration. Microstructure, interface properties, tensile behavior, and their relationships were investigated in detail. The results show the cross-weld tensile strength of the joints is up to 213 MPa, 95.5% of same Al weld. The optimal range of heat input for accepted joints was obtained as 83–98 J·mm−1. Within this range, the joint is stronger than 200 MPa and fractures in weld metal, or else, it becomes weaker and fractures at the intermetallic compounds (IMCs) layer. The IMCs layer of an accepted joint is usually thin and continuous, which is about 1μm-thick and only consists of TiAl2 due to fast solidification rate. However, the IMCs layer at the top corner of fusion zone/Ti substrate is easily thickened with increasing heat input. This thickened IMCs layer consists of a wide TiAl3 layer close to FZ and a thin TiAl2 layer close to Ti substrate. Furthermore, both bead shape formation and interface growth were discussed by laser-arc interaction and melt flow. Tensile behavior was summarized by interface properties.

Highlights

Growing concerns about weight reduction and rare metal saving have stimulated the joining of dissimilar metals
These findings denote that the interface reaction between molten pool and Ti sheet, especially the lower part depends on the laser, some arc heat is driven into the lower part by melt flow
Within the optimal range of heat input, accepted joints are stronger than 200 MPa and fracture in the FZ

Summary

Introduction

Growing concerns about weight reduction and rare metal saving have stimulated the joining of dissimilar metals. Joining aluminum (Al) and titanium (Ti) alloys is of interest to meet the requirement of high strength and low weight in aeronautic and automotive industries. Ti alloy is required to be fastened to Al fuselage in airplane fabrication. The challenges of Al/Ti joining come from the formation of brittle Al/Ti intermetallic compounds (IMCs) and characteristic difference between the two metals [1,2,3,4]. Precise thermal input is necessary to solve the problems caused by these differences in thermal characterization, as well as the growth brittle Al/Ti IMCs

Results

Discussion

Conclusion