Laser ultrasonics for metallurgy ( LUMet) is an innovative sensor technology for in-situ measurement of microstructure evolution during thermomechanical processing.Laser ultrasonics is a technique which is fast,remote and particularly adapted to measurements at high temperatures during complex thermomechanical processing paths.Recent advances in this technique will be illustrated with laboratory studies using a Gleeble 3500 thermomechanical simulator with a LUMet attachment.The LUMet technique has been used to measure austenite grain growth,austenite formation and decomposition in low-carbon steels during heating- cooling cycles,as well as ferrite recrystallization during annealing of cold-rolled steels.The LUMet measurements have been validated with conventional metallographic data.In particular,these studies have been focused on thermal cycles for the heat affected zone in an API-X80 linepipe steel as well as for intercritical annealing treatments of a DP600 steel that are typical for hot dip galvanizing lines.These examples are used to show the significance of this new sensor technology to accelerate the development of metallurgical process models for advanced steels.Even though a number of limitations exists,the LUMet system offers exciting opportunities for process development in the laboratory and process control in the plant.