Copper Based Bulk Metallic Glasses for Medical Devices

Bulk metallic glasses (BMGs) represent a viable alternative for replacing classic materials used in medical devices. This paper presents the research conducted in order to obtain copper based BMGs using two different chemical compositions: Cu48Zr47Al5 and Cu45Zr45Al5Ag5. The samples were obtained by copper mold casting and their structure and properties were investigated using X-Ray diffraction (XRD), differential scanning calorimetry (DSC) and optical microscopy.

Characterization and Corrosion Resistance of Boron-Containing-Austenitic Stainless Steels Produced by Rapid Solidification Techniques

The composition of a commercial duplex stainless steel was modified with boron additions (3.5, 4.5, and 5.5 wt.%) and processed by rapid-quenching techniques: Melt-spinning, copper-mold casting, and high-velocity oxygen fuel (HVOF). Spray deposition was also used to produce alloys as the process may induce rapid-solidified-like microstructures. These processing routes led to microstructures with distinguished corrosion resistance. Among the alloys with different boron contents, the 63.5Fe25Cr7Ni4.5B composition enabled the production of fully amorphous ribbons by melt-spinning. The cooling rate experienced during copper-mold casting, high-velocity oxygen fuel, and spray deposition did not ensure complete amorphization. The crystalline phases thereby formed were (Fe,Cr)2B and (Fe,Mo)3B2 borides in an austenitic-matrix with morphology and refinement dependent of the cooling rates. Fully amorphous 63.5Fe25Cr7Ni4.5B ribbons exhibited outstanding corrosion resistance in chloride-rich alkaline and acid media with negligible corrosion current densities of about 10−8 A/cm² and a broad passivation plateau. Although the specimens of the same composition produced by HVOF process and spray deposition exhibited lower corrosion resistance because of intrinsic porosity and crystalline phases, their corrosion behaviors were superior to those of AISI 1045 steel used as substrate with the advantage to be reinforced with hard borides known to be resistant against wear.

A Centimeter-Size High Toughness Zr-Cu-Al-Nb Bulk Metallic Glass with Nano-Crystallization and Phase Separation

In this paper, a centimeter-size Zr-Cu-Al-Nb bulk metallic glass (BMG) with high notch toughness of 107±13 MPa∙m0.5 was designed and fabricated by copper mold casting. With 1% Nb substitution for Zr in Zr48Cu45Al7 glass forming alloy, the glass forming ability (GFA) and toughness of the BMG were enhanced significantly. The coexistence of nano-crystallization and phase separation in the glassy matrix was observed in Zr47Cu45Al7Nb1, which would possibly lead to the high toughness of this alloy due to the easy and populous nucleation of shear bands and the increasing resistance of shear band propagation. The influences of nano-crystallization and phase separation on the toughness of BMGs are discussed in detail. The strategy utilized in this study provides a novel approach in search for new BMGs with high toughness and good GFA.

Studies on Fe-Cr-Ni-Si-B Bulk Metallic Glass for Automotive Applications

Researches and developments were carried out for obtaining of bulk metallic glass (BMG) from the Fe-Cr-Ni-Si-B system. The used processing methods were copper mold casting and melt spinning method. The resulted materials are in form of sheets with sizes of 69.7 x 64 x 3/1.5 mm and of strips with thickness less than 50 microns, which were obtained by varying the melt spin technological parameters. The both processing variants are not suitable for obtaining such of alloy in bulk metallic glass form. Adding of zirconium to this alloy produces bulk metallic glasses only for the melt spin products. The DSC analysis emphases that the zirconium modified alloy processed by melt spinning method exhibits a high glass forming ability (GFA).

Fe-Based Bulk Metallic Glass with Good Soft Magnetic Properties

Bulk Fe73Nb3Al2Ge2P9C6B4Si1 metallic glass with the diameter of 2 mm was prepared by copper mold casting. The Fe-based metallic glass exhibits good magnetic properties with high saturation magnetization and low saturated magnetostriction. The saturation magnetization and coercive force remains almost unchanged with annealing temperature below the crystallization temperature. The crystallization leads to the decrease in the softness of magnetic properties. The Fe-based glass exhibits a good correspondence between large glass-forming ability and good soft magnetic properties.

Surface Crystallization in Mg-Based Bulk Metallic Glass during Copper Mold Casting

The localized crystallization of Mg54Cu28Ag7Y11bulk metallic glass (BMG) in the injection casting process using a copper mold was investigated. It has been found that several crystalline phases were formed close to the as-cast surface but did not exist in the internal part of the BMG plate. It is abnormal that the as-cast surface is partially crystallized with higher cooling rate than that of inside. Overheating of the melt and nucleation induced by the surface of copper mold play key roles in the abnormal crystallization. It is suggested that the function of copper mold to trigger heterogeneous nucleation cannot be totally ignored, although it provides the high cooling rate for the glass formation during casting.