Abstract:
This thesis explored the susceptibility of ferritic/bainitic, advanced high strength steels to zinc-based liquid metal embrittlement (LME). The understanding of the causes and effects of LME is critical because of the common use of zinc coatings for corrosion protection and an increased used of advanced high strength steels in industries such as automotive. Transformation induced plasticity steels, TBF 1180 and TRIP 700, and a complex phase steel, CP 1200, were studied to assess their susceptibility to LME during hot tensile tests. Comparisons between stress versus strain curves collected with and without zinc coatings at various temperatures and strain rates were used to determine the effect of the zinc-based embrittlement on the mechanical properties of these steels. The stress versus strain curves were collected using uniaxial hot tensile tests in a Gleeble 1500D thermal-mechanical simulator from Dynamic Systems Inc. The fracture modes were studied using scanning electron microscopy and energy-dispersive X-ray spectrometry (EDS). From the results it was determined that all three steels demonstrated LME at temperatures between 800 C and 900 C and nominal strain rates of 1.3 and 0.13 strain per second. The fracture mode for all LME cracks was found to be intergranular.
