Some austenite crystals will remain unchanged even after quenching below the martensite finish (M) temperature. There is no thermal activation energy for the transformation from austenite to martensite. The strength of the martensite is reduced as the amount of retained austenite grows. Further excessive heat-treatment brings about the decomposition of the martensite and reversion to austenite. The R-phase is another martensitic phase that competes with the martensite phase mentioned above. Normalized steel consists of pearlite, martensite and sometimes bainite grains, mixed together within the microstructure. Tempering following quenching will transform some of the brittle martensite into tempered martensite. This reduces the amount of total martensite by changing some of it to ferrite. Cu phases in some aluminium alloys or martensite platlets in steel. These are fully quenched to martensite during processing. Below M, martensite formation under load allows superelasticity due to twinning. It is not possible to autogenous weld HY-80 due to the formation of untempered martensite. Too much martensite leaves steel brittle; too little leaves it soft. One mechanism that aids in this process is the twinning of the martensite phase. The slower cooling rate will reduce the likelihood of martensite formation.