Effect of Precipitate Size and Dispersion on Lankford Values of Titanium Stabilized Interstitial-free Steels

A quantitative study was undertaken to characterise the size, dispersion and microchemistry of precipitates and the texture of two hot-dip galvanised Ti stabilised interstitial free steels of comparable chemistry and grain size but with a distinct difference in Lankford values. Small angle neutron scattering technique was used complementary to electron optical techniques to resolve the ultra-fine precipitates (<5 mm). The specimen with a dense dispersion of fine precipitates exhibited a weak intensity of {111} texture and a low Lankford value. In order to clarify whether the development of {111} texture was suppressed by increased solute carbon in the matrix or by the Zener pinning force exerted by the ultra-fine precipitates during recrystallisation growth, internal friction measurements were carried out. The effect of ultrafine precipitates in retarding the grain boundary mobility is confirmed. The possible roles of solute carbon effect, and particle pinning effect on the evolution of {111} texture are discussed.