Microstructural Characterization by Color Tint Etching of a TRIP-800 Steel Welded by Laser CO
- PDF / 1,008,738 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 45 Downloads / 190 Views
Microstructural Characterization by Color Tint Etching of a TRIP-800 Steel Welded by Laser CO2 Process. G.Y. Pérez-Medina1, P. Zambrano2, H.F. López 1,F.A. Reyes-Valdés1. V H. López-Cortés1, 1 Corporación Mexicana de Investigación en Materiales Calle Ciencia y Tecnología #790, Fracc. Saltillo 400, Saltillo, Coah. México 25290 2
Universidad Autónoma de Nuevo León. Facultad de Ingeniería Mecánica y Eléctrica. Av. Pedro de Alba S/N. Col Ciudad Universitaria. San Nicolás de los Garza Nuevo León. ABSTRACT This paper presents results on the impact of Laser CO2 process variables on the weldability, phase transformations and exhibited tensile properties in a TRIP800 Steel. The microstructures of this steel consist of ferrite, bainite, martensite, and substantial amount of retained austenite, which is obtained by controlled cooling from the intercritical anneling temperature to the isothermal bainitic holding temperature. These steel has been increasingly used in the last 10 years in the automotive industries and for these materials to be used effectively, the influence of material and the Laser CO2 process condition must be clearly understood. Hence, in this work the effect of the welding process on the resultant microstructures and on the exhibited mechanical properties was investigated. Color tint etching applied in welded for AHSS help us to know the phase transformation, the colors of each phase viewed under the microscopy. The weld was etching with Klemm´s 1 solution, in this work; it was found that the bainite is clearly identify by blue color, the martensite brown, yellow ferrite and the retained austenite white. Additional X ray Diffraction (XRD) is employed in characterization to estimate the quantity of retained austenite. KEYWORDS: x-ray diffraction (XRD), Laser, Microstructure. INTRODUCTION In order to reduce automobile vehicle weight and enhance passenger safety, multiphase advanced high strength steel (AHSS) such as multiphase transformation-induced-plasticity (TRIP)-aided steels have been developed. These steel combine high strength with good formability. Their microstructure consist bainite (B), ferrite (F), martensite (M), and retained austenite (RA). Phase identification not possible with standard black and white micrographs is often possible with color micrographs. In the TRIP steel is difficult to distinguish the retained austenite because has minor than 13 vol pct [1,2], it’s important to know the volume fraction of retained austenite in base metal (BM), heat affected zone (HAZ) and fusion zone (FZ) when a TRIP is welded by laser CO2 process because when a tensile stress is applied to the steel, e.g. during tensile testing, deformation of car components or in a crash situation, the retained austenite in the strain concentration region will transform to martensite. Since the carbon hardening is much higher for the martensite than for the austenite phase and the volume expansion due to this transformation result in plastic deformation and work hardening of the surrounding ferrite, a localized strengtheni
Data Loading...
