We are treating TI64 sample at open air furnace, to get bimodal structure treating it at below beta (955oc ) and aging it at 700oc.we are getting the bimodal structure for different same but problem is that different sample has different grain size, approx two to three times.We are controlling the temperature closely, but getting the same problem. Can anyone suggest other possible factors which can affect the grain size variation for the sample to sample.