Pseudoelastic CoNiGa high-temperature shape memory alloys (HT-SMAs) show a wide range of transformation temperatures and lower processing costs than conventional Ni-Ti-X HT-SMAs which renders them useful for high temperature applications in automotive industries. Recent studies demonstrated stable functional properties from ambient temperature up to 200°C. In addition, heat treatments at intermediate temperatures promote the precipitation of γ´- particles which significantly increases the hardness of the austenite matrix. In particular the γ´ - particle morphology varies with ageing conditions and leads to functional properties which differ from the particle free material. In-situ mechanical tests at elevated temperatures are conducted using the SXD Laue Diffractometer to assess the detwinning mechanism and martensite twin domain relationships in depth.