tailieunhanh - Dtudy of effect of friction stir welding parameters on impact energy of AA7075-T6

The experimental results showed that, in all cases, the lowest impact energy is located at the stirred zone and that energy seems to be increased from the SZ to the HAZ across the welding. Furthermore, it is also found that the impact energy is decreased when the ratio of rotation speed to welding speed (ω/v) is increased. | Tạp chí Khoa học và Công nghệ 54 (1) (2016) 99-108 STUDY OF EFFECT OF FRICTION STIR WELDING PARAMETERS ON IMPACT ENERGY OF AA7075-T6 Duong Dinh Hao1, *, Tran Hung Tra1, Vu Cong Hoa2 1 Department of Engineering Mechanics, Nha Trang University, 02 Nguyen Dinh Chieu St., Nha Trang City, Vietnam 2 Department of Engineering Mechanics, Ho Chi Minh City University of Technology, 268 Ly Thuong Kiet St., District 10, Ho Chi Minh City, Vietnam * Email: dinhhao@ Received: 29 March 2015; Accepted for publication: 12 September 2015 ABSTRACT The influences of the tool rotation speed (denoted ω) and the welding speed (denoted v) on the impact energy at the representative zones in the friction stir welding (FSW) of AA7075-T6 were investigated. Here, the standard V–Notched specimens were applied in which the notches were addressed at the stirred zone (SZ), the heat affected zones (HAZ) in both the advancing side and the retreating side and the mixed zone (MZ). The experimental results showed that, in all cases, the lowest impact energy is located at the stirred zone and that energy seems to be increased from the SZ to the HAZ across the welding. Furthermore, it is also found that the impact energy is decreased when the ratio of rotation speed to welding speed (ω/v) is increased. The microstructure, the temperature distribution, and the hardness in and around the welded zone were considered and discussed. Keywords: friction stir welding, welding speed, temperature distribution, microstructure, hardness, impact energy. 1. INTRODUCTION Aluminum alloy 7075-T6 has a very high ultimate tensile strength of 572 MPa and yield strength of 503 MPa [1], and is used extensively in the aerospace industry along with others in the AA2xxx series (Fig. 1). They are, however, aluminum alloys which are considered unsuitable for arc welding. This is one of their weaknesses. In 1991, The Welding Institute (TWI) in the UK invented new technology – “friction stir welding” (FSW) (Fig. 2). .