THE EFFECT OF THERMOMECHANICAL PROCESSING ON THE CREEP BEHAVIOR AND FRACTURE TOUGHNESS OF THIXOMOLDED? AM60 ALLOY

摘要

Creep and fracture toughness experiments were performed on a commercially available magnesium-aluminum alloy (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 conventional tensile-creep experiments were performed at applied stresses ranging between 20-75MPa and temperatures between 373-473K (100-200℃). In-situ tensile-creep tests were performed on selected samples. The as-molded material exhibited creep resistance superior to the thermomechanically processed materials. Creep experiments indicated grain boundary cracking, and grain size was expected to be an important microstructural parameter that affected the creep behavior. Fracture toughness experiments were performed at room temperature (RT) on single edge notched tension (SENT) samples. The TTMP and annealed materials exhibited fracture toughness values almost twice that of the as-molded material.