Spark plasma sintering of iron based amorphous alloys, composites, and coatings

Amorphous alloys or bulk metallic glasses (BMG's) are new class of materials having superior mechanical properties when compared to conventional metals and alloys due to their disordered atomic structure. Fabrication of BMG's involves solidification at a very high rate which is difficult to attain for bulk samples (size > 10mm). This motivated researchers to find alternative techniques to fabricate bulk amorphous alloys. Spark plasma sintering (SPS) is one such processing technique where, simultaneous application of direct pulsed current and pressure activates the sintering process and compacts the material at a lower temperature (200-300 °C less) and within shorter sintering time (few minutes) than conventional sintering techniques like hot pressing and hot iso-static pressing. In this study, spark plasma sintering (SPS) technique is used to fabricate iron based amorphous alloys, composites, and coatings. Spark plasma sintering technique is used to fabricate highly dense fully amorphous iron based amorphous alloy below crystallization temperature (~600 °C) of the material. SPS is also used to fabricate in-situ and ex-situ iron based amorphous composite near crystallization temperatures. It was observed that temperature, pressure and reinforcement in amorphous alloys play significant role in densification of the BMG composites. Iron based amorphous composite coatings are successfully fabricated on aluminum substrate. This coating exhibited high micro-hardness (~1000 HV) and wear resistance (70-80 % higher) when compared to aluminum substrate. Fabrication of bulk metallic glass alloys, composites and coatings using SPS showed promising results and one of the best techniques. Moreover, as SPS takes short sintering time and lesser energy in fabrication of BMG, it present significant commercialization potential for bulk structural applications.