Currently there is renewal of interest in actuation functionality using high temperature shape memory alloys with transformation temperatures above 100°C (HTSMA) driven by strong demand for reliable and powerful actuators to be used in engines and gas turbines, where it is preferable to adopt single piece compact adaptive actuator over more complex multicomponent assemblies. The aim of this project is to clarify the reasons for poor dimensional and functional stability and fatigue failure of NiTiX actuators. The research will be performed by combination earlier developed and used methods (thermomechanical fatigue testing, in-situ X-ray and neutron diraction, TEM and micromechanics modeling) . The research will be coordinated with worldwide academic and industrial partners currently developing HTSMA actuators. Approaches to modify the microstructure of NiTiX alloys so so they act as well performing HTSMA actuators for 100°C-300°C temperature range will be proposed (adjustment of composition, degree of cold work, heat treatment, texture, grain size, precipitation strengthening).