THE EFFECT OF THERMOMECHANICAL PROCESSING ON THE TENSILE AND FATIGUE BEHAVIOR OF THIXOMOLDED® AM60

Tensile and fatigue experiments were performed at RT and 150 degrees C on AM60 after three processing treatments: (1) as-thixomolded (as-molded), (2) thixomolded then thermomechanically processed (TTMP), and (3) thixomolded then TTMP then annealed (annealed). The TTMP procedure resulted in a significantly reduced grain size and a tensile yield strength greater than twice that of the as-molded material without a debit in elongation-to-failure (epsilon(f)). The as-molded material exhibited the lowest strength while the annealed material exhibited an intermediate strength but the highest epsilon(f) (>19%). The as-molded material exhibited the lowest fatigue threshold values and the lowest fatigue resistance. The annealed material exhibited the greatest fatigue resistance and this was suggested to be related to its balance of tensile strength and ductility. Overall the results indicate that thermomechanically processing of AM60 dramatically improves the mechanical behavior making this alloy attractive for structural applications in the automotive, aerospace, wind energy, and biomedical industries.