摘要
High-pressure torsion(HPT)processing under a pressure of 6.0 GPa was applied to Ti29.7Ni50.3Hf20(at.%)alloy.Two types of structure were observed after HPT with 3 revolutions:first one is the mixture of amorphous phase and retained nanocrystalline;second is the alternating bands of amorphous phase and high defect density crystalline.As a result,post deformation annealing(PDA)at 500-700℃leads to the non-uniform distribution of martensite and parent phase grains.The grains of martensite are twice larger compared to that of parent phase.The nanocrystalline and ultrafine grains form after annealing at 500-600℃and 700℃,respectively.The twinning mechanism does not change with the reduction of martensitic grains up to^35 nm.The relationship between strength and grain size in Ti29.7Ni50.3Hf20 alloy obeys the classical Hall-Petch relationship with a coefficient of 10.80±0.39 GPa nm^1/2.
基金
supported by National Key R&D Program of China[grant number 2017YFE0123500]
National Natural Science Foundation of China[grant number 51971072,51671064]
the Fundamental Research Funds for the Central University[grant number HEUCFG201836]
the support from the RFBR-CNPq-DST research project№19-58-80018
the support in part from the Russian Foundation for Basic Research(project No.20-03-00614)。
