外文翻譯--2017-t351鋁合金攪拌摩擦焊接頭的拉伸性能和斷裂位置（英文）

1、Journal of Materials Processing Technology 142 (2003) 692–696Tensile properties and fracture locations of friction-stir-welded joints of 2017-T351 aluminum alloyH.J. Liu a,b,?, H. Fujii a, M. Maeda a, K. Nogi aa Joining

2、and Welding Research Institute, Osaka University, Osaka 567-0047, Japan b National Key Laboratory of Advanced Welding Production Technology, Harbin Institute of Technology, Harbin 150001, PR ChinaReceived 30 October 2002

3、; received in revised form 15 May 2003; accepted 5 June 2003AbstractFriction stir welding (FSW) is a new and promising welding process that can produce low-cost and high-quality joints of heat-treatable aluminum alloys b

4、ecause it does not need consumable filler materials and can eliminate some welding defects such as crack and porosity. In order to demonstrate the friction stir weldability of the 2017-T351 aluminum alloy and determine o

5、ptimum welding parameters, the relations between welding parameters and tensile properties of the joints have been studied in this paper. The experimental results showed that the tensile properties and fracture locations

6、 of the joints are significantly affected by the welding process parameters. When the optimum revolutionary pitch is 0.07 mm/rev corresponding to the rotation speed of 1500 rpm and the welding speed of 100 mm/min, the ma

7、ximum ultimate strength of the joints is equivalent to 82% that of the base material. Though the voids-free joints are fractured near or at the interface between the weld nugget and the thermo-mechanically affected zone

8、(TMAZ) on the advancing side, the fracture occurs at the weld center when the void defects exist in the joints. © 2003 Elsevier B.V. All rights reserved.Keywords: Friction stir welding; Tensile properties; Welding p

9、arameter; Aluminum alloy; Fracture location1. IntroductionHeat-treatable aluminum alloys are difficult to fusion weld because some welding defects such as crack and porosity are easily formed in the weld during the solid

10、- ification of the welding pool [1]. Friction stir welding (FSW) is a solid phase welding process in which the metal to be welded is not melted during the welding, thus the crack and porosity often associated with fusion

11、 welding processes are eliminated [1,2]. Therefore, the FSW pro- cess can be used to weld heat-treatable aluminum alloys in order to obtain high-quality joints [1–4]. However, many studies on the microstructural characte

12、ristics and mechan- ical properties of the friction-stir-welded joints have in- dicated that FSW gives rise to softening in the joints of the heat-treatable aluminum alloys such as 2014-T651 [5], 2024-T3 [6,7], 2024-T351

13、 [8,9], 2024-T6 [10,11], 2195-T8 [12,13], 6061-T5 [14,15], 6061-T6 [8,16–18], 6063-T5 [19–21], 6082-T5 [22], 7075-T651 [23] and 7475-T76 [7] because of the dissolution or growth of strengthening pre-? Corresponding autho

14、r. Tel.: +81-6-6879-8663. E-mail addresses: lhj@jwri.osaka-u.ac.jp, liuhj@hope.hit.edu.cn (H.J. Liu).cipitates during the welding thermal cycle, thus resulting in the degradation of the mechanical properties of the joint

15、s. Hence, it is important to study the effects of welding pro- cess parameters on the mechanical properties of the joints and determine the optimum welding parameters so as to obtain high-quality friction-stir-welded joi

16、nts. In the 2xxx-series heat-treatable aluminum alloys, 2014-T651, 2024-T3, 2024-T351 and 2024-T6 were fric- tion stir welded in order to examine the tensile proper- ties [5–8,11] or fracture locations [5,7,8] of the joi

17、nts. The 2017-T351 aluminum alloy is one of the 2xxx-series heat-treatable aluminum alloys and it has not been friction stir welded up to now. This paper aims to demonstrate its friction stir weldability and the emphasis

18、 is placed on the relations of the tensile properties and fracture locations of the joints to the welding parameters in order to determine the optimum FSW parameters and find out the weakest locations of the joints.2. Ex

19、perimental procedureThe base material used in this study was a 2017-T351 alu- minum alloy plate of 5 mm thick, whose chemical compo- sitions and mechanical properties are listed in Table 1. The0924-0136/$ – see front mat

20、ter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0924-0136(03)00806-9694 H.J. Liu et al. / Journal of Materials Processing Technology 142 (2003) 692–696RS AS00.10.20.3-15 -10 -5 0 5 10 15Distance from weld

21、 center, mmStrain0.02 mm/r 0.07 mm/r 0.27 mm/rFig. 2. Strain distributions in the typical joints.distributions of the joints welded at the different revolution- ary pitches. In this figure, the location at which the maxi

22、- mum strain of each joint occurs is the fracture location of the joint. In addition, the retreating side and advancing side of each joint are denoted by RS and AS, respectively. It is observed from Fig. 2 that the strai

23、n distributions of the joints are located in a comparatively narrow region and the strain values are considerably low. Especially, the fracture lo- cations of the joints are not distant from the weld center and change wi

24、th the revolutionary pitches. When the revolution- ary pitch is much smaller e.g. 0.02 mm/rev, the fracture loca- tion of the joint is only 4.1 mm from the weld center. When the revolutionary pitch increases to 0.07 mm/r

25、ev, the frac- ture location of the corresponding joint changes to 1.9 mm away. When the revolutionary pitch is equal to or greater than 0.27 mm/rev, the joints are all fractured at the weld cen- ter. That is to say, as t

26、he revolutionary pitch increases, the fracture location of the joint gradually approaches the weld center. These results indicate that the joints are fractured under the conditions of local and heterogeneous deformation,

27、 and the fracture locations of the joints are significantly affected by the welding parameters. Moreover, it should be noted that all the joints are fractured on the advancing side or at the weld center, but not on the r

28、etreating side of the joints. This implies that the tensile properties of the joints are not the same on the two sides of the weld center, and the tensileFig. 3. Cross-sections of the typical joints welded at the differe

29、nt revolutionary pitches: (a) 0.02 mm/rev; (b) 0.07 mm/rev; and (c) 0.27 mm/rev.RS AS 90110130150-20 -15 -10 -5 0 5 10 15 20Distance from weld center, mmVickers hardness, Hv0.02 mm/r 0.07 mm/r 0.27 mm/rFig. 4. Microhardn

30、ess distributions of the typical joints welded at the different revolutionary pitches.properties on the advancing side are weaker than those on the retreating side.3.2. DiscussionA softened region has been formed in the

31、joints of 2017-T351 aluminum alloy due to the effect of friction heat as occurred in the joints of other heat-treatable aluminum alloys [7,21–23]. The tensile properties and fracture loca- tions of the joints are, to a l

32、arge extent, dependent on the welding defects and hardness distributions of the joints, and which, in turn, on the welding parameters [6,11,14]. Figs. 3 and 4 show, respectively, the typical cross-sections and microhardn

33、ess distributions of the joints welded at the dif- ferent revolutionary pitches. When the revolutionary pitch is smaller than 0.13 mm/rev, FSW produces defect-free joints (see Fig. 3(a) and (b)). When the revolutionary p

34、itch is greater than 0.13 mm/rev, some void defects are formed in the joints because of the lack of heat input to the joints (see Fig. 3(c)). When such void defects exist in the joints, the tensile properties and fractur

35、e locations of the joints are significantly affected by the defects. In Fig. 4, the hardness values at the void locations do not exist and are expressed by “x”. These voids generally occur in the middle of the weld, thus