Mechanical and thermal stability of Bulk Metallic Glass alloys identified as candidates for space mechanism applications

Abstract

Extraterrestrial environments expose engineering components to severe operating conditions for extended durations. Challenges of extreme temperature changes and high vacuum are being met by careful selection of available materials or by development of novel high-performance materials and processes. Bulk Metallic Glasses (BMGs) are amorphous alloys that exhibit very high strengths, hardness, strain energy storage, corrosion resistance, and the capacity for thermoplastic formability, and are of interest in space engineering design. Using criteria driven by the requirements of specific space-based mechanisms, BMG alloys were selected from the literature for processing and performance evaluation. Alloys particularly suited for gearing applications and flexure-based compliant mechanisms were identified and standard test specimens produced. Four Zr-based BMG alloys were selected for analysis: Zr53Al16Co23.25Ag7.75, Cu47Zr46Al5Y2, Zr49Ti1.96Cu37.24Al9.8Y2, and Zr60Ti2Nb2Al7.5Ni10Cu18.5, with compositions in at.%. Presented in this work are the results of compression testing, fatigue testing, and differential scanning calorimetry; previous results of wear and hardness testing have been presented elsewhere. A maximum space service temperature of 400 °C is considered. The alloys exhibited significant differences in processability and thermomechanical performance. The alloy Zr49Ti1.96Cu37.24Al9.8Y2 exhibited the best overall performance for gearing applications; and Zr60Ti2Nb2Al7.5Ni10Cu18.5 was the best alloy for compliant flexures.

Keywords

• Fatigue
• Stress/strain measurements
• Thermal analysis
• Amorphous materials
• Design of space components
• Plasticity