外文翻譯-稀土元素對鎂合金的影響（英文）

1、Journal of Alloys and Compounds 481 (2009) 379–384Contents lists available at ScienceDirectJournal of Alloys and Compoundsjournal homepage: www.elsevier.com/locate/jallcomEffects of rare-earth elements Gd and Y on the so

2、lid solution strengthening of Mg alloysL. Gao a,b, R.S. Chen a,?, E.H. Han aa State Key Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, 62 Wencui Road,Shenyang 110016, P

3、eople’s Republic of Chinab Graduate School of the Chinese Academy of Sciences, Beijing 100049, People’s Republic of Chinaa r t i c l e i n f oArticle history:Received 31 December 2008Received in revised form 24 February

4、2009Accepted 26 February 2009Available online 13 March 2009Keywords:Mg–Gd–Y alloySolid solution strengtheningHall–Petch relationshipMechanical propertiesa b s t r a c tA number of Mg–Gd, Mg–Y binary and Mg–Gd–Y ternary a

5、lloys are investigated in terms of solid solutionstrengthening efficiency in this work. It is found that both gadolinium and yttrium in solid solution give acn concentration dependence of the yield strength, where c is t

6、he solute atom concentration and n = 1/2 or2/3. This simplified analysis illustrates that we are able to satisfactorily predict the ternary solid solutionstrengthening in Mg–Gd–Y alloys. Gd and Y in solid solution are fo

7、und to give a considerably higherstrengthening effect than Al and Zn. It is suggested that, in addition to the classical size and/or modulusmisfits model, the valency effect may account for the enhanced strengthening of

8、Gd and Y in Mg.© 2009 Elsevier B.V. All rights reserved.1. IntroductionMagnesium alloys have great potential to be used as structuralmaterials because they are the lightest among all the structuralalloys in use [1–1

9、2]. Compared with aluminum alloys, however, thestrength of magnesium alloys is still relatively low which limitstheir extensive application. To improve the mechanical propertiesof Mg alloy, Mg–RE (rare-earth elements, su

10、ch as Gd, Y, Ce, Nd,misch metal, etc.) alloys have been given tremendous attention dueto their high specific strength at both room and elevated tempera-tures as well as their excellent creep resistance [1,3,6,7,9,12]. Am

11、ongthem, Mg–Gd–Y system is one of the promising candidates for anovel Mg-based age hardenable alloy.In general, precipitation hardening and solid solution strength-ening are two major mechanisms for the strengthening by

12、REadditions to increase the strength of Mg alloys [13,14]. The struc-ture and morphology of the precipitate phases and the precipitationsequence in the Mg–Gd–Y alloys have been relatively well estab-lished [8,10,11,15].

13、However, solid solution strengthening in thissystem has not been investigated yet. Previous work [13,16,17]indicated that yttrium shows significantly higher solid solutionstrengthening efficiency than that of Zn or Al.In

14、 this work, the strength of a number of Mg–Gd, Mg–Y binaryand Mg–Gd–Y ternary solid solution alloys were investigated. The? Corresponding author. Tel.: +86 24 23926646; fax: +86 24 23894149.E-mail addresses: rongshichen@

15、yahoo.com, rschen@imr.ac.cn (R.S. Chen).aim of the work was to isolate the individual solid solution strength-ening effects of Gd and Y atoms and to predict the strength ofthe ternary solid solution alloys. Terms affecti

16、ng the strengtheningefficiency were also discussed.2. Experimental proceduresIn this study, a number of Mg–Gd, Mg–Y binary and Mg–Gd–Y ternary alloyswere investigated. The alloys were prepared from high purity magnesium

17、(99.97%),and Mg–25Gd (wt.%), Mg–25Y (wt.%) master alloys by melting in an electric resis-tance furnace at about 780 ?C under protection with an anti-oxidizing flux. The meltswere poured into a mild steel mould preheated

18、to 200–300 ?C with a diameter of100 mm. The chemical compositions were determined by using inductively coupledplasma atomic emission spectroscopy (ICP). All the alloys were solution treated at535–540 ?C for 1.5–9 h (see

19、Tables 1 and 2 for a full description), followed by quench-ing into hot water at ～70 ?C. The solution treatments were optimized according tothe Mg–Gd and Mg–Y binary phase diagram [18] and Mg–Gd–Y ternary phase dia-gram

20、[19,20] in order to make the secondary phase to dissolve into the Mg matrixcompletely.Tensile tests were performed at an initial stain rate of 1.0 × 10?3 s?1 at roomtemperature with an extensometer attached to the s

21、pecimen. Flat tensile specimenswith a gauge length of 25 mm and cross-section 3 × 6 mm2 were machined from thesolution treated material. Three specimens were used for each test condition toensure the reproducibility

22、 of the data.Hardness testing was carried out on a Vickers tester with a load of 500 g anda holding time of 15 s. Not fewer than 10 measurements were made for eachalloy. Both the hardness and tensile tests were conducted

23、 within hours of quench-ing.Specimens were etched in a 5 vol.% nital solution after mechanical polishingfor microstructural observation. The mean grain size (d) was measured by the lin-ear intercept method using the equa

24、tion d = 1.74L, where L is the linear interceptgrain size determined by optical microscopy [21]. At least 300 grain boundarieswere counted for each alloy with various Gd contents.0925-8388/$ – see front matter © 200

25、9 Elsevier B.V. All rights reserved.doi:10.1016/j.jallcom.2009.02.131L. Gao et al. / Journal of Alloys and Compounds 481 (2009) 379–384 381Fig. 2. Effect of concentration of Gd on the hardness of the Mg–Gd alloys. The ha

26、rd-ness of ternary Mg–Gd–Y alloys is plotted as a function of the total alloying content(Gd + Y) at.%. Error bars are standard deviations.There is little consensus on the magnitude of the Hall–Petchparameter, k, in Mg-ba

27、sed alloys, with values ranging from135 MPa ?m1/2 [8] to 1250 MPa ?m1/2 [24], and few studies [8]were conducted on the Hall–Petch relationship in Mg–Gd basedalloys. Therefore, some additional experiments were performed.T

28、he Mg–0.49 at.% Gd alloy melts were poured into three differ-Fig. 3. (a) Typical nominal stress–nominal strain curves for the studied Mg–Gdalloys. (b) Tensile properties of the Mg–Gd alloys as a function of the atom conc

29、en-tration of solute. ?0.2 is the 0.2% proof strength; ?UTS is the ultimate tensile strength;and εf is the elongation-to-failure.Fig. 4. Optical microstructure of Mg–0.49 at.% Gd alloy with different grain size, (a)d = 1

30、64 ?m, (b) d = 71 ?m, (c) d = 63 ?m by casting into three different moulds.ent moulds to obtain different cooling rate, and specimens withgrain size varying from ～63 ?m to 164 ?m were produced, as seenin Fig. 4. The nomi

31、nal stress–nominal strain curves obtained fromtensile tested specimens with different grain size at room temper-ature were presented in Fig. 5a. The specimens with the smallestgrain size (～63 ?m) exhibited the highest 0.

32、2% proof strength(～73.4 MPa), while 0.2% proof strength decreased with increasinggrain size (～71 ?m and ～164 ?m).The 0.2% proof strength of Mg–0.49 at.% Gd alloy exhibits grainsize dependence according to Hall–Petch rela

33、tionship, as shownin Fig. 5b. In the present study, the experimental Hall–Petch rela-tion is expressed as ?0.2 = 46.5 + 188d?1/2, namely, the ?0 andk are 46.5 MPa and 188 MPa ?m1/2, respectively, in the solu-tion treated