# Surface Forming Criteria of Ti-6 AL-4V Titanium Alloy under Laser Loading
## 1 Introduction  
Titanium alloy material is an important structural metal developed in the 1950s. The industrial production of titanium began in 1948, and the development of the aviation industry has led to rapid growth of the titanium industry. Countries are also developing new low-cost and high-performance titanium alloys, and strive to have titanium alloys enter the civil industry with huge market potential. In this context, higher requirements are put forward for the research into titanium alloy processing technology.  
Laser shock forming is developed on the basis of laser shock processing technology. The interaction between laser and material produces high-pressure plasma. The plasma blast wave maintained by the laser energy propagates into the target material to form a shock wave, and the shock wave strikes the metal target. The effect of the shock wave causes the target material to undergo plastic deformation [1]. Different from ordinary stamping molding technology, laser impact forming technology makes small-scale metal material molding processing production more economical, not only saving human resources and production costs, but is also more widely applicable than ordinary stamping molding technology, suitable for ordinary metal materials and some non-processable metal materials. In recent years, researchers have conducted a lot of research on the material modification and plastic deformation of commonly used metals such as copper, aluminum and stainless steel under laser shock technology [2; 3; 4]. The [PERSON] team of Jiangsu Universitystudied the influence of laser parameters and material selection on forming quality through a large number of experiments [5; 6]. The study found that the deformation of the target material is positively correlated with the laser pulse energy, as well as the number of laser shocks. For different materials, the effect of laser shock on the surface hardness and microstructure of the material was analyzed experimentally. [PERSON] of Beijing Institute of Aeronautical Manufacturing Engineering [7] conducted experiments to study the bending deformation law and surface characteristics of aluminum alloy under laser-induced shock wave loading, and the study found that laser power density and coverage affect the size and distribution of plastic strain on the surface of the sample, which affected its bending deformation. [PERSON]'s team from Jiangsu University [8] studied the thickness reduction rate criterion of aluminum alloy sheet under laser shock through simulation and experiment, and applied the fracture criterion to study the forming law of different sheet sizes under laser shock, and obtained the rule by studying the thickness reduction limit and forming depth limit of the sheet metal. [PERSON] [9], from Anhui University of Technology, studied the semi-membrane multi-impact forming process of 2024 aluminum alloy sheet under laser loading through a combination of experiment and simulation, and discussed the impact of shock wave pressure, sheet thickness and other factors on plate forming. [PERSON] [10] of Nanchang Aviation University used binary optics to change the distribution of laser spot light intensity, and discussed the forming limit and forming effect of 0.1 mm thickness titanium plates under different laser process parameters. However, the experimental research on these aspects of Ti-6 AL-4V(TC4) titanium alloy is somewhat insufficient.  
In this paper, TC4 titanium alloy is taken as the research object. The back deformation of the target material is measured by profilometer, and the influence of different laser parameters on the impact forming of the target material is compared. In addition, the whole process of laser impact is observed by a high-speed camera, and the causes of various phenomena at different times are analyzed. Moreover, the forming rules of TC4 titanium alloy under laser loading are obtained.