TEXTURAL CHANGES THROUGH GRAIN-GROWTH IN TI-BEARING IF-STEEL INVESTIGATED BY ORIENTATION IMAGING MICROSCOPY AND X-RAY-DIFFRACTION

Textural changes were investigated using X-ray diffraction and orienta tion imaging microscopy (OIM). During normal grain growth, slight incr ease in gamma-fibre (ND//[111]) was observed. Prolonged annealing and a resultant[rant abnormal grain growth, however, decreased gamma and i ncreased ct (RD//[110]). The decrease/increase in fibres were mainly c aused by corresponding changes in F [{111}[112]] and l [{112}[110]] or ientations, while E [{111}[110]] and H [{001}[110]] components did not change significantly. OIM characterization of grain boundary nature i ndicated an approximate increase in the fraction of low angle (<20 deg rees) boundaries with increasing annealing time;At the initiation of a bnormal grain growth, the fraction of low angle boundaries (specially those with 1-5 degrees misorientation) were observed to have reached a relatively large value. Such observations may fit well with a simple scheme: the transient strengthening in gamma-fibre was possibly caused by normal grain growth of;l-grains. Al the later stages of grain grow th, the growth of the gamma-grains was possibly inhibited/stopped by g rains of similar orientations. This, in turn, may increase the fractio n of low angle boundaries. When the fraction of low-angle/low-mobility boundaries reached a critical value, growth of certain grains (as F/E in our case) were inhibited/pinned, while few of the more favourable placed/oriented grains could grow abnormally. Measured values of 'free length', defined as the average distance between an i (where i may be F/E/I/H) and al (where j is less than 20 degrees misoriented with i) grain, showed the highest value for [ and the lowest for F. Free lengt h can be considered as an average distance for non-interrupted growth. Highest free length Values for I, caused by the spatial locations, po ssibly favored abnormal grain growth of i grains.