Trans. Nonferrous Met. Soc. China 27(2017) 1735−1746 Nd:YAG laser micro-welding of ultra-thin FeCo−V magnetic alloy: optimization of weld strength H. MOSTAAN 1 , M. SHAMANIAN 2 , S. HASANI 3 , M. SAFARI 4 , J. A. SZPUNAR 5 1. Department of Materials and Metallurgical Engineering, Faculty of Engineering, Arak University, Arak 38156-8-8349, Iran; 2. Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran; 3. Department of Mining and Metallurgical Engineering, Yazd University, Yazd 89195-741, Iran; 4. Department of Mechanical Engineering, Arak University of Technology, Arak 3818141167, Iran; 5. Department of Mechanical Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9, Canada Received 20 March 2016; accepted 13 September 2016 Abstract: The main aim of this research is to optimize the tensile strength of laser welded FeCo−V alloy. A mathematical relationship was developed to predict tensile strength of the laser beam welded FeCo−V foils by incorporating process parameters such as lamping current, welding speed, pulse duration and focused position. The procedure was established to improve the weld strength and increase the productivity. The results indicate that the pulse duration and welding speed have the greatest influence on tensile strength. The obtained results showed that the tensile strength of the weld joints increase as a function of increasing pulse duration reaching to a maximum at a pulse duration value of 2.25 ms. Moreover, the tensile strength of joints increases with decrease in welding speed reaching to a maximum at a welding speed of 125 mm/min. It has been shown that increase in pulse duration and decrease in welding speed result in increased effective peak power density and hence formation of more resistant welds. At higher pulse durations and lower welding speeds, the tensile strength of weld joints decreases because of formation of solidification microcracks in the fusion zone. Key words: Nd:YAG laser welding; FeCo−V magnetic alloys; response surface methodology; mechanical properties; optimization 1 Introduction FeCo-based alloys have attracted considerable attention due to their excellent soft magnetic properties as well as high Curie temperature, high saturation induction and low magnetic core loss [1−3]. For high performance applications in many fields such as rotor or stator laminations in motors for power generation, such magnetic materials are required to possess not only the abovementioned magnetic properties but also good mechanical properties, such as high strength and ductility [4,5]. During the past few years a considerable amount of research has been devoted to these alloys in order to develop optimum magnetic and mechanical properties for application in modern aircraft generators. However, binary Fe−Co alloys remained without industrial applications, mainly because of its extreme brittleness. It has been discovered that the addition of vanadium to those alloys can have beneficial effects on the ductility and strength without serious degradation of the magnetic properties [6]. These magnetic alloys with 50%−52% Co and 5%−13% V revealed in the first half of the 20th century, which are called “vicalloy” [7], belong to the group of magnetically hard materials. Depending on the amount of vanadium, the coercive force of the alloys varies at 4.0−24.0 kA/m, the residual induction is between 1.25 and 0.6 T [8]. A distinguishing feature of FeCo−V alloys is their high plasticity, which enable us to obtain the above indicated magnetic properties in metallic ribbons up to 50 μm in thickness. This fact, along with the high temperature stability of magnetic characteristics, makes them suitable for some applications such as active parts of rotors of synchronous hysteresis motors (SHM) [8]. In order to deploy these magnetic alloys in SHMs, it is necessary to produce them in the form of ultra-thin foils. This requirement has been raised with the goal of obtaining increasingly denser and Corresponding author: H. MOSTAAN; Tel: +988632625005: Fax: +988632774031, E-mail: H-mostaan@araku.ac.ir DOI: 10.1016/S1003-6326(17)60196-1