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Bulk glass formation and mechanical properties for Cu–Hf–Ti–M (M = B,Y) alloys
Journal of Non-Crystalline Solids 353 (2007) 839–841 www.elsevier.com/locate/jnoncrysol
Bulk glass formation and mechanical properties for Cu–Hf–Ti–M (M = B,Y) alloys I.A. Figueroa a, R. Rawal a, P. Stewart b, P.A. Carroll c, H.A. Davies a,*, H. Jones a, I. Todd a a
Department of Engineering Materials, University of Sheffield, Mappin Street, Sheffield S1 3JD, UK b BAE Systems Ltd., Wharton, Lancs, UK c TWI (Yorkshire) Ltd., Catcliffe, Rotherham, UK Available online 20 February 2007
Abstract The glass forming ability (GFA), nanohardness Hn and Young’s modulus E of ternary alloys in the compositional series Cu60Hf40 xTix (x = 5–35) are reported and discussed. Bulk glass formation was observed for the three alloys x = 17.5, 20 and 22.5, with critical rod diameters dc for a fully glassy structure of 4, 4 and 3 mm, respectively. A dc of 4 mm was also observed for the Cu55Hf25Ti20 alloy. These compositions generally had the highest values of reduced glass temperature while no correlation was observed between the GFA and the parameter DTx. Both Hn and E surprisingly showed minima at 20 at.%Ti for the Cu60Hf40 xTix series. The addition of 1 at.%B or Y to the Cu60Hf22.5Ti17.5 alloy slightly decreased the GFA but slightly increased the elastic modulus. 2007 Elsevier B.V. All rights reserved. PACS: 61.43.dq; 62.20. x; 81.05.Kf Keywords: Amorphous metals, metallic glasses; Alloys; Liquid alloys and liquid metals; Transition metals; Mechanical properties; Hardness; Indentation; Microindentation; Short-range order
1. Introduction Bulk glass formation in ternary Cu–Ti–Zr alloys was first reported in 2001 [1]. Alloys in the isomorphous system Cu–Ti–Hf can also be cast as bulk glasses [2,3] and are of interest because of their potentially higher thermal stability and strength than their Cu–Zr–Ti counterparts. The composition Cu60Ti15Hf25 [2], for instance, has a tensile fracture strength of 2130 MPa, combined with plastic elongation of around 1.6%. Moreover, the addition of Zr [4] or Nb [5] to Cu–Hf–Ti alloys increases their glass forming ability (GFA), with fully glassy rods of diameter 5 mm being castable. In the present paper, we report and discuss
*
Corresponding author. Tel.: +44 (0)114 222 5518; fax: +44 (0)114 222 5943. E-mail address: h.a.davies@sheffield.ac.uk (H.A. Davies). 0022-3093/$ - see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2006.12.068
initial results of a study of GFA and mechanical properties for the alloy series Cu60Hf40 xTix and for Cu55Hf25Ti20 and also the influence of small additions of B or Y on these properties. 2. Experimental procedure Cu-based alloy ingots having compositions of Cu60Hf40 xTix (x = 5–35), Cu55Hf25Ti20 and (Cu60Hf22.5Ti17.5)100 xMx (M = Y,B) were prepared by argon arc melting mixtures of Cu (99.99% pure), Hf (99.8% pure), Ti (99.98% pure), Y (99.99% pure) and B (99.98% pure). The alloy compositions represent the nominal values but the weight losses in melting were negligible (<0.1%). Cylindrical alloy rods, of length 50 mm and having either stepped diameters of 4, 3 and 2 mm or a single diameter of 5 mm, were produced by copper mould, suction-casting within the argon arc furnace [3].
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Ribbon samples with a cross section typically of 0.03 mm · 2.0 mm were also produced by chill-block melt spinning in a sealed argon atmosphere. The rod and ribbon structures were examined by XRD and the glass transition (Tg) and crystallisation (Tx) temperatures determined by DSC (Perkin–Elmer DSC7) at a heating rate of 0.33 K/s. The liquidus temperatures (Tl) were measured by DTA (Perkin–Elmer DTA-7) at a heating rate of 0.33 K/s. The hardness Hn and the Young’s modulus E of 2 mm diameter rod samples of the alloys were derived from nanoindenter measurements (Hysitron Triboscope). Fig. 1. Plot of Trg (Tg/Tl) for Cu60Hf40 xTix alloy series.
3. Results and discussion Table 1 gives the critical rod diameters, the thermal properties, Tg, Tx, Tl and the reduced glass temperature Trg (=Tg/Tl), for alloys in the series Cu60Hf40 xTix with x in the range 5–35. Only for the three alloys x = 17.5, 20 and 22.5 could fully glassy rods of diameter in the range 2–4 mm be cast, with no crystalline phase detected either by XRD or from etched metallographic cross sections of the rods. The remaining compositions could be vitrified only as melt spun ribbon. Increasing the Ti:Hf ratio results in rapid decreases in Tg and Tx, as would be expected [6] from the fact that the melting point and cohesive energy for Ti are substantially lower than for Hf. The values of Trg are plotted against the Ti content x in Fig. 1; the value peaks at x = 20. The data are in satisfactory agreement with those of Inoue et al. [2], except that the latter are consistently slightly larger than the present values. The three bulk glass forming alloys thus have compositions spanning the peak in Trg. The composition Cu55Hf25Ti20, for which the critical glassy rod diameter was found to be close to 5 mm, also had a Trg of 0.61. Thus, there is good correlation between the GFA and the measured Trg. The usefulness of Trg as a figure of merit in predicting GFA for non-bulk glass forming metallic alloys is well established [6] but the limitations of using such a simple single parameter for predicting GFA for bulk glass forming compositions, having very low critical cooling rates for glass formation, particularly across a diverse range of alloy systems, have subsequently been emphasized [7]. Nevertheless, for the present single alloy Table 1 Glass forming section thickness and thermal properties for the Cu60Hf40 xTix (x = 5–35) alloy series Composition
dc (mm)
Tg (K)
Tx (K)
DTx (K)
Tl (K)
Trg
Cu60Hf35Ti5 Cu60Hf30Ti10 Cu60Hf25Ti15 Cu60Hf22.5Ti17.5 Cu60Hf20Ti20 Cu60Hf17.5Ti22.5 Cu60Hf15Ti25 Cu60Hf10Ti30 Cu60Hf5Ti35
<0.03 <0.03 <0.03 4–5 4–5 3–4 <0.03 <0.03 <0.03
775 751 748 745 740 732 722 700 690
828 806 788 780 767 755 745 726 712
53 55 40 35 27 23 23 26 22
1333 1263 1240 1234 1211 1229 1223 1233 1223
0.58 0.59 0.6 0.6 0.61 0.59 0.59 0.56 0.56
system, the correlation between GFA and Trg is surprisingly good, probably because the crystalline phases which are being suppressed by glass formation do not change over the composition range 5–35 at.%Ti. In contrast, the parameter DTx (=Tx Tg), which has been proposed as a predictive parameter for GFA [8], shows an overall continuous decrease between x = 5 and 35, allowing for experimental scatter, and thus does not correlate with the GFA. The liquidus temperature Tl has its minimum value for the 20 at.%Ti alloy, probably corresponding to a ternary eutectic, since only this composition has a single melting peak in the DTA trace, and, clearly, this is a dominating factor in determining that Trg has its maximum value at this composition. The atomic diameter of Ti (0.146 nm) is intermediate between those of Cu (0.127 nm) and Hf (0.157 nm) and, evidently, equal proportions of Hf and Ti result in maximum stabilization of the densely packed liquid structure. The addition of 1 at.%B slightly reduced the glass forming ability (GFA) for the Cu60Hf22.5Ti17.5, to a critical rod diameter (dc) of 3 mm, while 3 at.%B reduced dc to <2 mm. The B additions resulted in markedly reduced Tg, to 693 and 670 K for 1 and 3 at.%, respectively, accompanied by reductions in Tl of only 20 K. Thus, Trg was substantially reduced to 0.57 and 0.55 by the 1 and 3 at.%B additions, respectively, but without causing dramatic reduction in GFA. Clearly, addition of the fourth atomic species causes a step change in the relation between GFA and Trg, possibly because of a change in the crystalline phases being suppressed. A fully glass structure was found for rods of diameter 2 mm on addition of 1 at.%Y to Cu60Hf22.5Ti17.5. The Young’s modulus E of alloy rods in the series Cu60Hf40 xTix, determined from nanoindentation measurements, is plotted for the range of x = 15–25 in Fig. 2. Also plotted is the value of nanohardness Hn. The 15 and 25 at.%Ti rod samples, however, contained some crystalline phase(s) which would be expected, in any case, to result in increased E. Both parameters showed an apparent minimum at 20 at.%Ti, which is rather surprising, considering that Tg decreases continuously between x = 5 and 35. For a homogeneous glass structure, devoid of crystalline microstructure, it has previously been found that thermal stability, expressed by Tg or Tx, correlates quite well with
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and 2 mm, respectively. Generally, the alloys having the highest values of Trg had the highest GFA, whereas no correlation was found between GFA and DTx. The values of nanohardness and E for the Cu60Hf40 xTix series were surprisingly found to have minima at 20 at.%Ti. Acknowledgments IAF is grateful for the financial support of the Mexican Council of Science and Technology (Conacyt), through scholarship No. 205146. HAD and HJ acknowledge financial support of part of the work by QinetiQ, Farnborough. Valuable technical support provided by Mr P. Hawksworth is also acknowledged. References Fig. 2. Plot of the elastic modulus E and Nanohardness for the 2 mm cast Cu60Hf40 xTix alloy rods.
mechanical properties, including Hv and E, at least within a particular alloy system [9]. The addition of 1 at.%B and Y to the Cu60Hf22.5Ti17.5 glass increased E by about 2% which was barely significant. The effect of B on Hn again was very small, 2% increase, while the Y resulted in a significant decrease of 5%. 4. Conclusions Several compositions in the system Cu–Ti–Hf system, including Cu60Ti17.5Hf22.5, and Cu55Ti20Hf25, which had not previously been reported, were found to be bulk glass formers as rods >3 mm diameter. The addition of small concentrations of B or Y decreased slightly rather than enhanced the GFA, to yield glassy rods of diameter 3
[1] A. Inoue, W. Zhang, T. Zhang, K. Kurosaka, Mater. Trans. 42 (2001) 1149. [2] A. Inoue, W. Zhang, T. Zhang, K. Kurosaka, J. Mater. Res. 16 (2001) 2836. [3] I.A. Figueroa, H.A. Davies, I. Todd, J. Alloys Compd., in press. [4] A. Inoue, W. Zhang, T. Zhang, K. Kurosaka, Acta Mater. 49 (2001) 2645. [5] C. Qin, W. Zhang, K. Asami, N. Ohtsu, A. Ionue, Acta Mater. 53 (2005) 3903. [6] H.A. Davies, Phys. Chem. Glasses 17 (1976) 159. [7] H.A. Davies, in: M. Vazquez, A. Hernando (Eds.), Nanostructure and Non-Crystalline Materials, World Scientific, Singapore, 1995, pp. 3–14. [8] A. Inoue, Bulk Amorphous Alloys: Preparation and Fundamental Characteristics, Mater. Sci. Foundations, No. 6, Trans. Tech. Publications, Switzerland, 1998. [9] I.W. Donald, H.A. Davies, Phil. Mag. 42 (1980) 277; I.W. Donald, S.H. Whang, H.A. Davies, B.C. Giessen, in: T. Masumoto, K. Suzuki (Eds.), Proceedings of the fourth International Conference Rapidly Quenched Metals, Sendai, The Japan Institute Metals, 1982, pp. 1377–1380.
Bulk glass formation and mechanical properties for Cu–Hf–Ti–M (M = B,Y) alloys I.A. Figueroa a, R. Rawal a, P. Stewart b, P.A. Carroll c, H.A. Davies a,*, H. Jones a, I. Todd a a
Department of Engineering Materials, University of Sheffield, Mappin Street, Sheffield S1 3JD, UK b BAE Systems Ltd., Wharton, Lancs, UK c TWI (Yorkshire) Ltd., Catcliffe, Rotherham, UK Available online 20 February 2007
Abstract The glass forming ability (GFA), nanohardness Hn and Young’s modulus E of ternary alloys in the compositional series Cu60Hf40 xTix (x = 5–35) are reported and discussed. Bulk glass formation was observed for the three alloys x = 17.5, 20 and 22.5, with critical rod diameters dc for a fully glassy structure of 4, 4 and 3 mm, respectively. A dc of 4 mm was also observed for the Cu55Hf25Ti20 alloy. These compositions generally had the highest values of reduced glass temperature while no correlation was observed between the GFA and the parameter DTx. Both Hn and E surprisingly showed minima at 20 at.%Ti for the Cu60Hf40 xTix series. The addition of 1 at.%B or Y to the Cu60Hf22.5Ti17.5 alloy slightly decreased the GFA but slightly increased the elastic modulus. 2007 Elsevier B.V. All rights reserved. PACS: 61.43.dq; 62.20. x; 81.05.Kf Keywords: Amorphous metals, metallic glasses; Alloys; Liquid alloys and liquid metals; Transition metals; Mechanical properties; Hardness; Indentation; Microindentation; Short-range order
1. Introduction Bulk glass formation in ternary Cu–Ti–Zr alloys was first reported in 2001 [1]. Alloys in the isomorphous system Cu–Ti–Hf can also be cast as bulk glasses [2,3] and are of interest because of their potentially higher thermal stability and strength than their Cu–Zr–Ti counterparts. The composition Cu60Ti15Hf25 [2], for instance, has a tensile fracture strength of 2130 MPa, combined with plastic elongation of around 1.6%. Moreover, the addition of Zr [4] or Nb [5] to Cu–Hf–Ti alloys increases their glass forming ability (GFA), with fully glassy rods of diameter 5 mm being castable. In the present paper, we report and discuss
*
Corresponding author. Tel.: +44 (0)114 222 5518; fax: +44 (0)114 222 5943. E-mail address: h.a.davies@sheffield.ac.uk (H.A. Davies). 0022-3093/$ - see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2006.12.068
initial results of a study of GFA and mechanical properties for the alloy series Cu60Hf40 xTix and for Cu55Hf25Ti20 and also the influence of small additions of B or Y on these properties. 2. Experimental procedure Cu-based alloy ingots having compositions of Cu60Hf40 xTix (x = 5–35), Cu55Hf25Ti20 and (Cu60Hf22.5Ti17.5)100 xMx (M = Y,B) were prepared by argon arc melting mixtures of Cu (99.99% pure), Hf (99.8% pure), Ti (99.98% pure), Y (99.99% pure) and B (99.98% pure). The alloy compositions represent the nominal values but the weight losses in melting were negligible (<0.1%). Cylindrical alloy rods, of length 50 mm and having either stepped diameters of 4, 3 and 2 mm or a single diameter of 5 mm, were produced by copper mould, suction-casting within the argon arc furnace [3].
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I.A. Figueroa et al. / Journal of Non-Crystalline Solids 353 (2007) 839–841
Ribbon samples with a cross section typically of 0.03 mm · 2.0 mm were also produced by chill-block melt spinning in a sealed argon atmosphere. The rod and ribbon structures were examined by XRD and the glass transition (Tg) and crystallisation (Tx) temperatures determined by DSC (Perkin–Elmer DSC7) at a heating rate of 0.33 K/s. The liquidus temperatures (Tl) were measured by DTA (Perkin–Elmer DTA-7) at a heating rate of 0.33 K/s. The hardness Hn and the Young’s modulus E of 2 mm diameter rod samples of the alloys were derived from nanoindenter measurements (Hysitron Triboscope). Fig. 1. Plot of Trg (Tg/Tl) for Cu60Hf40 xTix alloy series.
3. Results and discussion Table 1 gives the critical rod diameters, the thermal properties, Tg, Tx, Tl and the reduced glass temperature Trg (=Tg/Tl), for alloys in the series Cu60Hf40 xTix with x in the range 5–35. Only for the three alloys x = 17.5, 20 and 22.5 could fully glassy rods of diameter in the range 2–4 mm be cast, with no crystalline phase detected either by XRD or from etched metallographic cross sections of the rods. The remaining compositions could be vitrified only as melt spun ribbon. Increasing the Ti:Hf ratio results in rapid decreases in Tg and Tx, as would be expected [6] from the fact that the melting point and cohesive energy for Ti are substantially lower than for Hf. The values of Trg are plotted against the Ti content x in Fig. 1; the value peaks at x = 20. The data are in satisfactory agreement with those of Inoue et al. [2], except that the latter are consistently slightly larger than the present values. The three bulk glass forming alloys thus have compositions spanning the peak in Trg. The composition Cu55Hf25Ti20, for which the critical glassy rod diameter was found to be close to 5 mm, also had a Trg of 0.61. Thus, there is good correlation between the GFA and the measured Trg. The usefulness of Trg as a figure of merit in predicting GFA for non-bulk glass forming metallic alloys is well established [6] but the limitations of using such a simple single parameter for predicting GFA for bulk glass forming compositions, having very low critical cooling rates for glass formation, particularly across a diverse range of alloy systems, have subsequently been emphasized [7]. Nevertheless, for the present single alloy Table 1 Glass forming section thickness and thermal properties for the Cu60Hf40 xTix (x = 5–35) alloy series Composition
dc (mm)
Tg (K)
Tx (K)
DTx (K)
Tl (K)
Trg
Cu60Hf35Ti5 Cu60Hf30Ti10 Cu60Hf25Ti15 Cu60Hf22.5Ti17.5 Cu60Hf20Ti20 Cu60Hf17.5Ti22.5 Cu60Hf15Ti25 Cu60Hf10Ti30 Cu60Hf5Ti35
<0.03 <0.03 <0.03 4–5 4–5 3–4 <0.03 <0.03 <0.03
775 751 748 745 740 732 722 700 690
828 806 788 780 767 755 745 726 712
53 55 40 35 27 23 23 26 22
1333 1263 1240 1234 1211 1229 1223 1233 1223
0.58 0.59 0.6 0.6 0.61 0.59 0.59 0.56 0.56
system, the correlation between GFA and Trg is surprisingly good, probably because the crystalline phases which are being suppressed by glass formation do not change over the composition range 5–35 at.%Ti. In contrast, the parameter DTx (=Tx Tg), which has been proposed as a predictive parameter for GFA [8], shows an overall continuous decrease between x = 5 and 35, allowing for experimental scatter, and thus does not correlate with the GFA. The liquidus temperature Tl has its minimum value for the 20 at.%Ti alloy, probably corresponding to a ternary eutectic, since only this composition has a single melting peak in the DTA trace, and, clearly, this is a dominating factor in determining that Trg has its maximum value at this composition. The atomic diameter of Ti (0.146 nm) is intermediate between those of Cu (0.127 nm) and Hf (0.157 nm) and, evidently, equal proportions of Hf and Ti result in maximum stabilization of the densely packed liquid structure. The addition of 1 at.%B slightly reduced the glass forming ability (GFA) for the Cu60Hf22.5Ti17.5, to a critical rod diameter (dc) of 3 mm, while 3 at.%B reduced dc to <2 mm. The B additions resulted in markedly reduced Tg, to 693 and 670 K for 1 and 3 at.%, respectively, accompanied by reductions in Tl of only 20 K. Thus, Trg was substantially reduced to 0.57 and 0.55 by the 1 and 3 at.%B additions, respectively, but without causing dramatic reduction in GFA. Clearly, addition of the fourth atomic species causes a step change in the relation between GFA and Trg, possibly because of a change in the crystalline phases being suppressed. A fully glass structure was found for rods of diameter 2 mm on addition of 1 at.%Y to Cu60Hf22.5Ti17.5. The Young’s modulus E of alloy rods in the series Cu60Hf40 xTix, determined from nanoindentation measurements, is plotted for the range of x = 15–25 in Fig. 2. Also plotted is the value of nanohardness Hn. The 15 and 25 at.%Ti rod samples, however, contained some crystalline phase(s) which would be expected, in any case, to result in increased E. Both parameters showed an apparent minimum at 20 at.%Ti, which is rather surprising, considering that Tg decreases continuously between x = 5 and 35. For a homogeneous glass structure, devoid of crystalline microstructure, it has previously been found that thermal stability, expressed by Tg or Tx, correlates quite well with
I.A. Figueroa et al. / Journal of Non-Crystalline Solids 353 (2007) 839–841
841
and 2 mm, respectively. Generally, the alloys having the highest values of Trg had the highest GFA, whereas no correlation was found between GFA and DTx. The values of nanohardness and E for the Cu60Hf40 xTix series were surprisingly found to have minima at 20 at.%Ti. Acknowledgments IAF is grateful for the financial support of the Mexican Council of Science and Technology (Conacyt), through scholarship No. 205146. HAD and HJ acknowledge financial support of part of the work by QinetiQ, Farnborough. Valuable technical support provided by Mr P. Hawksworth is also acknowledged. References Fig. 2. Plot of the elastic modulus E and Nanohardness for the 2 mm cast Cu60Hf40 xTix alloy rods.
mechanical properties, including Hv and E, at least within a particular alloy system [9]. The addition of 1 at.%B and Y to the Cu60Hf22.5Ti17.5 glass increased E by about 2% which was barely significant. The effect of B on Hn again was very small, 2% increase, while the Y resulted in a significant decrease of 5%. 4. Conclusions Several compositions in the system Cu–Ti–Hf system, including Cu60Ti17.5Hf22.5, and Cu55Ti20Hf25, which had not previously been reported, were found to be bulk glass formers as rods >3 mm diameter. The addition of small concentrations of B or Y decreased slightly rather than enhanced the GFA, to yield glassy rods of diameter 3
[1] A. Inoue, W. Zhang, T. Zhang, K. Kurosaka, Mater. Trans. 42 (2001) 1149. [2] A. Inoue, W. Zhang, T. Zhang, K. Kurosaka, J. Mater. Res. 16 (2001) 2836. [3] I.A. Figueroa, H.A. Davies, I. Todd, J. Alloys Compd., in press. [4] A. Inoue, W. Zhang, T. Zhang, K. Kurosaka, Acta Mater. 49 (2001) 2645. [5] C. Qin, W. Zhang, K. Asami, N. Ohtsu, A. Ionue, Acta Mater. 53 (2005) 3903. [6] H.A. Davies, Phys. Chem. Glasses 17 (1976) 159. [7] H.A. Davies, in: M. Vazquez, A. Hernando (Eds.), Nanostructure and Non-Crystalline Materials, World Scientific, Singapore, 1995, pp. 3–14. [8] A. Inoue, Bulk Amorphous Alloys: Preparation and Fundamental Characteristics, Mater. Sci. Foundations, No. 6, Trans. Tech. Publications, Switzerland, 1998. [9] I.W. Donald, H.A. Davies, Phil. Mag. 42 (1980) 277; I.W. Donald, S.H. Whang, H.A. Davies, B.C. Giessen, in: T. Masumoto, K. Suzuki (Eds.), Proceedings of the fourth International Conference Rapidly Quenched Metals, Sendai, The Japan Institute Metals, 1982, pp. 1377–1380.