Modeling of Grain Structure and Heat-Affected Zone in Laser Surface Melting Process
- PDF / 713,291 Bytes
- 8 Pages / 593.972 x 792 pts Page_size
- 22 Downloads / 152 Views
NTRODUCTION
THE application of lasers is becoming of increasing interest to materials processing such as cutting,[1,2] welding,[3,4] and surface modification.[5,6] It is characterized by a high power density of 108 to 109 W/m2 at the target surface. Such a high energy is deposited only in a very thin layer within a short time, which leads to rapid heating and melting, followed by rapid solidification. Because of the thermal cycle associated with melting and solidification, the microstructure of material near the welded region may undergo considerable changes.[7] Grain growth in the heat-affected zone (HAZ) is the most important example that can lead to a decrease in mechanical properties of the weld joints.[8] Although laser melting processes are generally characterized by small HAZ, there is still much interest in understanding and, hence, controlling the development of grain structure in these processes. In general, several welding process variables influence the microstructural characteristics of the HAZ in welding or surface melting. This has been demonstrated in numerous studies by various researchers, mostly using mathematical modeling. A summary of these studies is given next. Gunaraj and Murugan[9] developed a mathematical model to study the effects of wire feed rate, welding speed, nozzle to plate distance, and heat input on HAZ in submerged arc welding of pipes. Sista et al.[10] used Monte Carlo method to simulate grain growth in HAZ. They showed a linear relationship between HAZ grain size and heat input of the respective welding process. Yang et al.,[11] Shome,[12] Moon et al.,[13] and Aval et al.[14] also used various analytical and numerical models to study the effect of heat input MOHAMMAD AMIN JABBAREH, Ph.D. Student, and HAMID ASSADI, Professor, are with the Department of Materials Engineering, Tarbiat Modares University, Tehran, Iran. Contact e-mail: ha10003@ modares.ac.ir Manuscript submitted October 4, 2012. Article published online March 29, 2013. METALLURGICAL AND MATERIALS TRANSACTIONS B
on the grain structure of HAZ. Benyounis et al.[15] studied the effect of laser power, focal point position, and welding speed on HAZ width to find optimum welding conditions in laser welding of medium carbon steel. Kong et al.[16] studied the effect of laser scanning speed on mean grain size and martensite volume fraction in HAZ of laser heat treatment of D980 steel. Using a three-dimensional finite-element heat transfer model, Yang et al.[17] investigated the effect of laser parameters on HAZ geometry of laser-assisted machining of Ti-6Al4V alloy. They found that the depth and width of the HAZ were strongly dependent on the laser power, laser scan speed, the angle of incidence, and the diameter of laser spot. Using a similar method, Fang et al.[18] and Lacki and Adamus[19] investigated the effect of laser power and scanning speed on geometry of HAZ in laser cladding and electron beam welding process, respectively. Thiessen et al.[20] utilized a phase field model to simulate austenitization in HAZ of gas tungsten arcwelde
Data Loading...
