Early Stage Material Motion and Transient Optical Properties of Metals after Ultrashort Laser Pulse Irradiation

Abstract

Use of lightweight materials to produce automotive body structures is one of the key trends adopted by automotive manufacturers to minimise emission of greenhouse gases, and subsequently, reduction of fuel consumption. Aluminium alloys are one of the promising lightweight materials which are increasingly used for automotive body-in-white structures. Such applications demand both efficient and effective joining/welding methods to produce repeatable, durable and strong joints without significant alteration of material properties. Remote laser welding (RLW) is an emerging joining technology and increasingly being used to produce lightweight joints as it satisfies the demand for high production throughput at low cost. This paper investigates the effects of process parameters when seam tracking remote laser welding is used to create an autogenous fillet edge weld of automotive grade aluminum alloy (AC-170PX) in lap configuration without shielding gas. The effects of laser power and welding speed on the key geometric features are reported together with details of the weld microstructure. Joint strength is evaluated by performing a lap shear test. It is found that the laser power and welding speed have dominant influence on key geometric features and subsequently on the lap shear strength. Relatively larger grain size in the fusion zone reduces the microhardness by up to 20% in comparison with the base material.

Ultrafast laser platform providing dynamic peak power and energy deposition control: from laser source to industrial applications

“…Shorter pulses do not result in a further increase of ablation efficiency. This trend for ultrashort pulsed material ablation of opaque materials is well known [5,6] and can be linked to a change in laser induced stress and pressure waves inside the material [7], influencing photomechanical ablation mechanisms. In [4] it is shown that the pulse duration itself can also have an effect on ablation quality.…”