A Gold-Based Bulk-Solidifying Amorphous Alloy for Jewelry — Comparison with a Palladium-Based Amorphous Alloy

The gold alloys are used in jewelry for their aesthetic appearance and inertia to the environment. In jewelry a hardness superior to 300 HV is desirable to facilitate the final machining and reduce the wear of the final product. The maximum hardness that can be obtained with the standard 18 carats gold (Au75-Ag12.5-Cu12.5 (wt%)) through a combination of heat treatment and cold working is about 290 HV. Gold-based bulk metallic glasses (BMGs) are an alternative as they present unique properties in comparison with crystalline counterparts, especially easy thermoplastic processing combined with a high hardness. Pd-base BMGs are another solution, due also to their attractive features.An Au49Cu26.9Si16.3Ag5.5Pd2.3 (% at.) and a Pd40Cu30Ni10P20 (% at.) bulk metallic glasses were fabricated by a copper mould suction casting technique in an argon atmosphere. In the as-cast state hardness, shear modulus and hardness are high (HV0.3= 360 and 530 in the Au-and Pd-base BMGs, respectively). Various heat treatments have been performed to modify the microstructural state. Formation of crystalline particles induces an increase of both shear modulus and hardness but a drastic decrease in toughness and therefore this formation should be absolutely avoided during casting or thermo processing.

Download Full-text

A Conflict of Fineness and Stability: Platinum- and Palladium-Based Bulk Metallic Glasses for Jewellery

Johnson Matthey Technology Review ◽

10.1595/205651321x16045078967011 ◽

2020 ◽

Author(s):

O. S. Houghton ◽

A. L. Greer

Keyword(s):

Metallic Glasses ◽

Bulk Metallic Glasses ◽

Precious Metals ◽

High Hardness ◽

Scratch Resistance ◽

Cast State ◽

High Definition ◽

Glass Forming ◽

Thermoplastic Forming ◽

Near Net Shape

For the metals used in jewellery, high hardness and the associated scratch resistance are much sought after. Conventional crystalline alloys for jewellery are alloyed and extensively processed (thermally and mechanically) to improve hardness, but it is difficult to reach values beyond 300 HV. The advent of bulk metallic glasses, based on precious metals and with hardness exceeding 300 HV in the as-cast state, is therefore of great interest for both jewellery and watchmaking. The non-crystalline structure of these materials not only gives high hardness, but also the opportunity to shape metals like plastics, via thermoplastic forming. For more traditional jewellery manufacture, bulk metallic glasses also exhibit high-definition and near-net-shape casting. Gold-based alloys have long dominated the consideration of bulk metallic glasses for jewellery as they can comply with 18K hallmarks. Although bulk metallic glasses based on platinum or palladium possess excellent thermoplastic formability, and are without known tarnishing problems, achieving useful glass-forming ability within the more restrictive hallmarking standards typically used for jewellery (≥95 wt.% Pt or Pd) is, at best, challenging. In this review, platinum- and palladium-based bulk metallic glasses are discussed, focusing on their potential application in jewellery and on the further research that is necessary.

Download Full-text

Additive Manufacturing of Bulk Metallic Glasses—Process, Challenges and Properties: A Review

Metals ◽

10.3390/met11081279 ◽

2021 ◽

Vol 11 (8) ◽

pp. 1279

Author(s):

Navid Sohrabi ◽

Jamasp Jhabvala ◽

Roland E. Logé

Keyword(s):

Mechanical Properties ◽

Additive Manufacturing ◽

Metallic Glasses ◽

Small Volume ◽

Review Paper ◽

Bulk Metallic Glasses ◽

Amorphous State ◽

High Hardness ◽

Complete Understanding ◽

High Cooling Rates

Bulk Metallic Glasses (BMG) are metallic alloys that have the ability to solidify in an amorphous state. BMGs show enhanced properties, for instance, high hardness, strength, and excellent corrosion and wear resistance. BMGs produced by conventional methods are limited in size due to the high cooling rates required to avoid crystallization and the associated detrimental mechanical properties. Additive manufacturing (AM) techniques are a potential solution to this problem as the interaction between the heat source, e.g., laser, and the feedstock, e.g., powder, is short and confined to a small volume. However, producing amorphous parts with AM techniques with mechanical properties comparable to as-cast samples remains a challenge for most BMGs, and a complete understanding of the crystallization mechanisms is missing. This review paper tries to cover recent progress in this field and develop a thorough understanding of the correlation between different aspects of the topic. The following subjects are addressed: (i) AM techniques used for the fabrication of BMGs, (ii) particular BMGs used in AM, (iii) specific challenges in AM of BMGs such as the control of defects and crystallization, (iv) process optimization of mechanical properties, and (v) future trends.

Download Full-text

Magnetic Properties and Glass Forming Ability of Fe-B-Y-Nb-Zr Bulk Metallic Glasses

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.577.27 ◽

2012 ◽

Vol 577 ◽

pp. 27-30 ◽

Cited By ~ 2

Author(s):

San Xin Wang ◽

Ze Yu Wu

Keyword(s):

Thermal Stability ◽

Magnetic Properties ◽

Metallic Glasses ◽

Bulk Metallic Glasses ◽

Supercooled Liquid Region ◽

Glass Forming Ability ◽

Maximum Diameter ◽

Liquid Region ◽

Casting Technique ◽

Glass Forming

Bulk metallic glasses (BMGs) alloys (Fe71.2B24Y4.8)96Nb4-xZrx (x = 1-4 at.%) with a maximum diameter of 5 mm were synthesized with low purity materials by copper mold casting technique. The effect of Zr substitution for Nb on the structure, thermal stability and the magnetic properties has been studied. It was found that the substitution of an appropriate amount of Zr for Nb can improve the glass forming ability. The wide supercooled liquid region ∆Tx (exceeding 123 K) and a high Tg (exceeding 868 K) demonstrated a high thermal stability of the present Fe-based BMGs. In addition, these BMGs also exhibit good soft magnetic properties with relatively high saturation magnetization of 88 emu/g, and low coercivity of 20 Oe.

Download Full-text

Structure and Properties of Zr-Based Bulk Metallic Glasses in As-Cast State and After Laser Welding

Materials ◽

10.3390/ma11071117 ◽

2018 ◽

Vol 11 (7) ◽

pp. 1117 ◽

Cited By ~ 9

Author(s):

Wirginia Pilarczyk

Keyword(s):

Laser Welding ◽

Metallic Glasses ◽

Bulk Metallic Glasses ◽

Structure And Properties ◽

Cast State

Download Full-text

Theoretical prediction of temperature dependent shear modulus of bulk metallic glasses

Intermetallics ◽

10.1016/j.intermet.2017.08.013 ◽

2017 ◽

Vol 91 ◽

pp. 86-89 ◽

Cited By ~ 1

Author(s):

Xianhe Zhang ◽

Weiguo Li ◽

Ying Li ◽

Jianzuo Ma ◽

Yong Deng ◽

...

Keyword(s):

Shear Modulus ◽

Theoretical Prediction ◽

Metallic Glasses ◽

Bulk Metallic Glasses ◽

Temperature Dependent

Download Full-text

Rejuvenation of Zr-Based Bulk Metallic Glasses by Ultrasonic Vibration-Assisted Elastic Deformation

Materials ◽

10.3390/ma13194397 ◽

2020 ◽

Vol 13 (19) ◽

pp. 4397

Author(s):

Yan Lou ◽

Shenpeng Xv ◽

Zhiyuan Liu ◽

Jiang Ma

Keyword(s):

Amorphous Alloy ◽

Free Volume ◽

Elastic Deformation ◽

Ultrasonic Vibration ◽

Metallic Glasses ◽

Bulk Metallic Glasses ◽

Supercooled Liquid ◽

Deformation Region ◽

Vibration Stress ◽

The Relationship

The rejuvenation of Zr52.5Cu17.9Ni14.6Al10Ti5 bulk metallic glasses (BMGs) by ultrasonic vibration-assisted elastic deformation (UVEF) was studied herein. The UVEF-treated samples demonstrate an obvious rejuvenation and have a higher relaxation enthalpy and a smaller range of supercooled liquid regions than the as-cast samples. The fracture of the rejuvenated amorphous alloy is mainly ductile fracture, and shear deformation occurs in the deformation region. It is also found that as the amplitude increases, the free volume of the rejuvenated amorphous alloy increases, the yield strength and the elastic modulus decrease, and the formability increases. The free-volume content is used to characterize the degree of rejuvenation, and a mathematical model of the relationship between the ultrasonic amplitude and free volume is established. In addition, it is found that the ultrasonic vibration stress induces the additional free volume in the Zr-based bulk metallic glasses and improves the plasticizing behavior. The temperature rise caused by the ultrasonic thermal effect does not induce additional free volume.

Download Full-text

Structural, Magnetic and Crystallization Study of Fe-Based Bulk Metallic Glasses

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.203-204.288 ◽

2013 ◽

Vol 203-204 ◽

pp. 288-291 ◽

Cited By ~ 5

Author(s):

Rafał Babilas ◽

Ryszard Nowosielski ◽

Wirginia Pilarczyk ◽

Grzegorz Dercz

Keyword(s):

Magnetic Properties ◽

Magnetic Permeability ◽

Metallic Glasses ◽

Bulk Metallic Glasses ◽

Annealing Process ◽

Bulk Amorphous Alloy ◽

X Ray Diffraction ◽

Cast State ◽

Scanning Calorimetry ◽

Crystallization Study

The work presents the structural, thermal and magnetic properties analysis of Fe72B20Si4Nb4 bulk metallic glasses in as-cast state and crystallization study of bulk amorphous alloy after annealing process. The studies were performed on bulk metallic glasses in of rods form with diameter of 1,5 and 2 mm. The structure analysis of the samples in as-cast state and phase analysis of studied alloy after annealing process was carried out by the X-ray diffraction (XRD) methods. Mössbauer spectroscopy (MS) was also used to investigate the local structure for studied bulk metallic glasses. Thermal properties associated with glass transition, onset and peak crystallization temperatures was examined by differential scanning calorimetry (DSC). The soft magnetic properties examination of tested material contained initial magnetic permeability and disaccommodation of magnetic permeability.

Download Full-text

Improving plasticity and toughness of Cu-Zr-Y-Al bulk metallic glasses via compositional tuning towards the CuZr

Journal of Materials Research ◽

10.1557/jmr.2010.0031 ◽

2010 ◽

Vol 25 (2) ◽

pp. 375-382 ◽

Cited By ~ 17

Author(s):

Yong Shen ◽

Jian Xu

Keyword(s):

Shear Modulus ◽

Intermetallic Compounds ◽

Metallic Glasses ◽

Bulk Metallic Glasses ◽

Critical Diameter ◽

Glass Forming Ability ◽

Al Alloys ◽

Simple Approach ◽

Glass Forming ◽

Tie Line

In this work, we propose a simple approach for designing plastic bulk metallic glasses (BMGs) by exploiting the ductility of intermetallic compounds involved in the BMG-forming system. Its validity was examined by investigating a series of quaternary Cu-Zr-Y-Al alloys along the composition tie-line between Cu42Zr44.4Y3.6Al10 (Y1) and the B2 CuZr phase, expressed as (Cu0.5Zr0.5)x(M)100-x (M = Zr0.15Y0.225Al0.625, 84≤x≤93). When tuning the composition towards the CuZr, the glass-forming ability of alloys is dramatically degraded, showing a reduction of critical diameter Dc for BMG formation from 16 mm at x = 84 (Y1) to 2 mm at x = 93. As the composition of BMGs shifts to the CuZr terminal, the shear modulus μ of the BMGs decreases, whereas the Poisson's ratio ν increases. With respect to the Y1 BMG, compressive plasticity and toughness of the Y2 BMG (x = 92, Dc = 4 mm) with a higher concentration of the CuZr are improved, which is consistent with its lower μ and higher ν values.

Download Full-text