“Role of atomic packing in glass forming ability and stability of ternary and some quaternary bulk metallic glasses”

In this work we study the influence of atomic packing efficiency on glass-forming ability of bulk (defined as 3-dimentional massive glassy articles with a size of not less than 1 mm in any dimension) metallic glasses by the analysis of a database of ternary and quaternary bulk metallic glasses. An extensive dataset on the composition and stability (critical thickness, glass-transition temperature, crystallization temperature and liquidus temperature) of ternary and quaternary metallic glasses has been obtained from the literature data. The results indicate that glassy alloys compositions are distributed in a highly non-uniform way in the compositional area and tend to prefer specific values of fraction and atomic size ratios. For example in ternary alloys clear maxima are seen at about A65B15C20, A70B10C20, A65B10C25, A40B18C38, A45B17C28 and A58B13C45 compositions. Clear minimum at A50B25C25 corresponds to the A2BC compound, while A60B5C35 and A75B5C20 compositions are close to A2C and A3C binary compounds, respectively. Glass-forming ability is shown to increase with increasing the number of alloying elements. According to the statistical analysis one can anticipate that the difference in Dc among binary, ternary and quaternary alloys is meaningful which confirms the first Inoue’s principle for achieving high GFA. Quaternary bulk glass-forming alloys with large critical diameter in general have larger Tx than those of ternary alloys and are preferable for shaping in SCLR. As Tg and Tx for ternary and quaternary alloys nearly linearly depends on Tl, one may anticipate that it is not a coincidence but real physical meaning on structural unity of the bulk-glass-forming alloys. The data on glass-forming ability and thermal stability were collected for ternary and quaternary bulk metallic glasses. Only metallic glasses produced by solidification from the melt are considered. The data for binary bulk metallic glasses have been taken from our earlier paper. Data for similar alloys from different literature sources with slightly different reported properties were also collected. The data retrieved from the literature separately for ternary and quaternary alloys include alloy composition, critical thickness (rod sample diameter) for single glassy phase formation, the glass-transition, crystallization temperatures and liquidus temperatures, namely Tg, Tx and Tl, respectively. The compositions used in the present review are usually nominal compositions given by the pre-melting weight of the elements. Common thermal stability parameters, including Trg=Tg/Tl, Tx=Tx-Tg and  Tx/(TgTl) were calculated from Tg, Tx and Tl. We collected the data from an extensive number of literature sources on ternary (709 data points Fig. 1 represents the final part of the database) and quaternary (418 data points Fig. 2 represents the final part of the database) bulk metallic glassy alloys to find relation between the glass-forming ability (GFA), alloy composition and other parameters. The number of data points containing critical diameter was 93 and 212, respectively. The efficient cluster packing (ECP) model was used to establish the role of defect state and packing efficiency on metallic glass stability. Analysis of defects was also possible in the ECP structure, the most important are those associated with the filling of the inter-cluster sites. Structure and topology are inter-related in the ECP model to give a self-consistent description for a particular metallic glass. The structure of metallic glasses is related these to the glass stability and formability. Topological structure is obtained from the composition of the metallic glass, which gives both the atomic species (and hence atomic sizes) and concentrations. The critical diameter of ternary bulk glassy sample is plotted in Fig. 3 as a function of element B and C content in A-B-C alloys. Some clear maxima are seen at about A65B15C20, A70B10C20, A65B10C25, A40B18C38, A45B17C28 and A58B13C45 (less clear) compositions. One can also mention clear minima at the following compositions: A50B25C25, A60B5C35, A55B15C30, A46B7C47 and A75B5C20. A50B25C25 corresponds to the A2BC compound, while A60B5C35 and A75B5C20 compositions are close to A2C and A3C binary compounds, respectively. Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. 1. REPORT DATE 29 MAR 2010 2. REPORT TYPE Final 3. DATES COVERED 11-03-2009 to 25-03-2010 4. TITLE AND SUBTITLE Role of atomic packing in glass forming ability and stability of ternary and some quartenary bulk metallic glasses 5a. CONTRACT NUMBER FA23860914032