Abstract: The erosion behaviour of TiNi alloy foils (Ni: 50.5 at pct, thickness: 70~90μm) under various heat treatments has been studied with two different tests: sand-blasting erosion (SBE) with impingement angle of 30°and slurry erosion (SE). The erosion resistance of the foils aged at 400~450℃/30 min is the best in all tests. The quenched foil is also good in the SBE test, but not so good in the SE test. The slurry-erosion resistance of the aged foils is better than that of L214 with high hardness. All the foils exhibit much better erosion resistance than 18Cr-8Ni stainless steel in the tests