This article provides a history of electron and laser beam welding, discusses the properties of electrons and photons used for welding, and contrasts electron and laser beam welding. It presents a comparison of the electron and laser beam welding processes. The article also illustrates constant power density boundaries, showing the relationship between the focused beam diameter and the absorbed beam power for approximate regions of keyhole-mode welding, conduction-mode welding, cutting, and drilling.

Laser-beam welding (LBW) is a joining process that produces coalescence of material with the heat obtained from the application of a concentrated coherent light beam impinging upon the surface to be welded. This article describes the steps that must be considered when selecting the LBW process. It reviews the individual process variables that influence procedure development of the LBW process. Joint design and special practices related to LBW are discussed. The article concludes with a discussion on the use of consumables and special welding practices.

This article provides an overview of the fundamentals, mechanisms, process physics, advantages, and limitations of laser beam welding. It describes the independent and dependent process variables in view of their role in procedure development and process selection. The article includes information on independent process variables such as incident laser beam power and diameter, laser beam spatial distribution, traverse speed, shielding gas, depth of focus and focal position, weld design, and gap size. Dependent variables, including depth of penetration, microstructure and mechanical properties of laser-welded joints, and weld pool geometry, are discussed. The article also reviews the various injuries and electrical and chemical hazards associated with laser beam welding.

Most welding lasers fall into the category of fiber, disc, or direct diode, all of which can be delivered by fiber optic. This article provides a comparison of the energy consumptions and efficiencies of laser beam welding (LBW) with other major welding processes. It discusses the two modes of laser welding: conduction-mode welding and deep-penetration mode welding. The article reviews the factors of process selection and procedure development for laser welding. The factors include power density, interaction time, laser beam power, laser beam diameter, laser beam spatial distribution, absorptivity, traverse speed, laser welding efficiency, and plasma suppression and shielding gas. The article concludes with a discussion on laser cutting, laser roll welding, and hybrid laser welding.

Electron beam machining (EBM) uses a focused beam of high-velocity electrons to remove material. This article provides a description of equipment used for EBM and discusses the process characteristics, applications, advantages, and disadvantages of electron beam drilling.

Hybrid laser arc welding (HLAW) is a metal joining process that combines laser beam welding (LBW) and arc welding in the same weld pool. This article provides a discussion on the major process variables for two modes of operation of HLAW, namely, stabilization mode and penetration mode. The major process variables for either mode of operation include three sets of welding parameters: the variables for the independent LBW and gas metal arc welding processes and welding variables that are specific to the HLAW process. The article discusses the advantages, limitations, and applications of the HLAW and describes the major components and consumables used for HLAW. The components include the laser source, gas metal arc welding source, hybrid welding head, and motion system. The article also describes the typical sources of defects and safety concerns of HLAW.

Microjoining with high energy density beams is a new subject in the sense that the progress of miniaturization in industry has made the desire to make microjoints rapidly and reliably a current and exciting topic. This article summarizes the current state of microjoining with both electron and laser beams. It considers the elementary physical processes such as heat and fluid flow to introduce the reader to the phenomena that affect melting, coalescence, and solidification needed for a successful microweld. The various forces driving (and resisting) fluid flow are analyzed. The article discusses the equipment suitable for microjoining and the metallurgical consequences and postweld metrology of the process. It also provides examples of developmental welds employing laser and electron beam microwelding techniques.

Laser has found its applications in cutting, drilling, and shock-peening operations of manufacturing industry because of its accurate, safe, and rapid cutting property. This article provides an account on the fundamental principles of laser cutting (thermal), drilling, and shock-peening processes of which emphasis is placed on thermal laser cutting. It details the principal set-up parameters, such as the laser beam output, nozzle design, focusing optic position and characteristics, assist gases, surface conditions, and cutting speed. A discussion on the types of gas, supply system, purity level, and flow rates of lasing and assist gases is also provided. The article also describes the metallurgies and other key material considerations that impact laser-cutting performances and includes examples of laser cutting of nonmetal materials.

Laser soldering uses a well-focused, highly controlled beam to deliver energy to a desired location for a precisely measured length of time. This article focuses on two types of laser soldering operations, namely, blind laser soldering and intelligent laser soldering. It discusses the function of the blind laser soldering and provides a brief description on key attributes of the blind laser soldering, including repeatability, speed, quality, safety, and flexibility. The article explores the function of the intelligent laser soldering and concludes with a section on key attributes of the intelligent laser soldering. The key attributes of the intelligent laser soldering include repeatability, speed, quality, safety, cost, and flexibility.

Laser beam machining removes, melts, or thermally modifies a material by focusing a coherent beam of monochromatic light on the workpiece. This article describes the principal lasers used in metal processing: neodymium-glass, carbon dioxide, and neodymium-doped yttrium aluminum garnet lasers. It discusses the operating parameters of concern in percussion drilling and trepanning. The process variables in surface treatment and laser cutting, as well as the operating parameters of concern in laser welding are reviewed. The article also explains the various categories of surface treatment: heat treating, cladding, surfacing, glazing, and marking.

This article discusses the advantages, disadvantages, applications, and selection criteria of various technologies and transduction modalities that can generate and detect ultrasonic waves. These include piezoelectric transducers, electromagnetic acoustic transducers (EMATs), laser ultrasound phased array transducers, magnetostriction transducers, and couplants. The article discusses four basic types of search units with piezoelectric transducers. These include the straight-beam contact type, the angle-beam contact type, the dual-element contact type, and the immersion type. The article concludes with information on immersion or contact type focused search units.

Acoustical holography is the extension of holography into the ultrasonic domain. The basic systems for acoustical holography are the liquid-surface type and the scanning type. This article discusses the applications for acoustical holography, including inspection of large composite parts, through-transmission breast imaging system, inspection of welds in thick materials, and inspection of sleeve-bearing stock. It describes the basic system for liquid-surface acoustical holography and scanning acoustical holography. A comparison between these techniques is also provided.

This article is intended to provide the reader with a good understanding of the underlying science, technology, and the most common applications of focused ion beam (FIB) instruments. It begins with a survey of the various types of FIB instruments and their configurations, discusses the essential components, and explains their function only to the extent that it helps the operator obtain the desired results. An explanation of how the components of ion optical column shape and steer the ion beam to the desired target locations is then provided. The article also reviews the many diverse accessories and options that enable the instrument to realize its full potential across all of the varied applications. This is followed by a detailed analysis of the physical processes associated with the ion beam interacting with the sample. Finally, a complete survey of the most prominent FIB applications is presented.

The primary goal of quality control in electron beam (EB) welding is to consistently produce defect-free and structurally sound welds. This article discusses the common procedures for controlling the EB welding process, the control of the essential machine parameters, and the introduction of closed-loop controls and diagnostic feedback systems in the EB welding systems. It reviews the beam diagnostic tools that interrogate the beam to produce a reconstruction of the power density distribution and provide additional information on the size and shape of the EB. Knowledge of these beam parameters can be used to improve process understanding and control. The article also describes the application areas of beam diagnostics: machine characterization, weld parameter transfer, and weld quality control.

This article describes the use of conventional machining techniques, laser cutting and water-jet cutting for producing finished composite parts. It explains two representative polymer-matrix composites--graphite and aramid composites--and discusses the machining and drilling problems such as delamination and fiber or resin pullout. The article describes machining and drilling techniques and the necessary tools and cutting parameters. It presents a description of laser cutting. The article also provides information on the advantages, disadvantages, cutting characteristics, and applications of water-jet cutting and abrasive water-jet cutting.

Cutting with lasers is accomplished with carbon dioxide (CO 2 ) and neodymium: yttrium-aluminum-garnet (Nd:YAG) lasers. This article provides a description of the process variables and principles of laser cutting. It discusses the three basic types of CO 2 gas lasers, namely, slow axial flow, transverse flow, and fast axial flow and reviews the applications of Nd:YAG laser. The article describes the basic parameters in the laser-cutting process: beam quality, power, travel speed, nozzles design, and focal-point position. Several material conditions that affect the quality of the laser cut are also discussed. The article provides information on the basic laser-cutting system and its optional equipment. A general description of how well each metal group can be cut is also provided.

This article introduces the operating principles and modes of operation for high-vacuum (EBW-HV), Medium-vacuum (EBW-MV), and nonvacuum (EBW-NV) electron beam welding. Equipment, process sequence, part preparation, process control, and weld geometry are described for electron beam welding. Advantages are described in terms of welding near heat sensitive components or materials and producing deep penetration or shallow welds with the same equipment.

The effective integration of aluminum metal-matrix composites (Al-MMCs) into useful structures and devices often requires an understanding of the weldability of Al-MMCs that includes a thorough knowledge on the effects of various interactions between matrix and reinforcement. This article provides a detailed discussion on weldability and the effect of viscosity, chemical reactions, and solidification on weldability. It discusses different welding processes, namely, gas-tungsten arc welding, gas-metal arc welding, laser-beam welding, electron-beam welding, resistance welding, friction welding, transient liquid phase bonding, and capacitor discharge welding.

Electron-beam welding (EBW) is a high-energy density fusion process that is accomplished by bombarding the joint to be welded with an intense (strongly focused) beam of electrons that have been accelerated up to velocities 0.3 to 0.7 times the speed of light at 25 to 200 kV, respectively. This article discusses the principles of operation, as well as the advantages and limitations of EBW. It reviews the basic variables employed for controlling the results of an electron-beam weld. These include accelerating voltage, beam current, welding speed, focusing current, and standoff distance. The article reviews the operation sequence and safety aspects of EBW.