A Study On The Multiaxial Mechanical Properties Of Zirconium Alloys At Room Temperature

Zirconium alloys have been extensively applied in chemical industry,nuclear industry,naval architecture and other fields due to a combination of properties of low neutron absorption cross-section,high corrosion resistance,excellent mechanical strength and anti-radiation performance.The paper aims to explore the mechanical properties and ratcheting behaviors of industrial pure zirconium and zirconium niobium alloys under multiaxial loads.The study will be of important theoretical and practical significance to guide the applications of zirconium alloys.Uniaxial and multiaxial tension tests were conducted on industrial pure zirconium to discover tensile mechanical properties of the material.In the uniaxial tension tests both in rolling direction?RD?and in transverse direction?TD?,anisotropy coefficient r-values of zirconium alloy sheets were calculated and some basic mechanical properties were obtained.In biaxial tension tests of cruciform zirconium alloy specimen,the effects of multiaxial stress on material macroscopic deformation were studied under varied stress ratios and strain paths change.Equal plastic work contours of zirconium alloy sheets were compared with the theoretical predictions based on von Mises yield criterion,comparisons with the Hill'48 yield criterion were also made.The microstructure observations of zirconium alloy sheets showed limited number of twins,indicating that dislocation dominates deformation mechanism of zirconium alloy sheets in uniaxial tension.However,abundant tension twins were activated in biaxial tension,indicating that twinning is the dominant plastic deformation mechanism of zirconium alloy sheets.Uniaxial and multiaxial ratcheting tests,were also conducted zirconium alloy tubes under combined axial load and internal pressure at room temperature.The experimental results showed that in uniaxial symmetrical cyclic tests,the axial strain ratcheted significantly as the material was subjected to a symmetrical cyclic loading.In multiaxial ratcheting tests,zirconium alloy tubes were highly sensitive to both the axial stress amplitude?_xa and the internal pressure p_i.The hoop ratcheting strain??increased continuously with the increase of axial stress amplitude,whereas the evolution of axial ratcheting strain?_x was related to the axial stress amplitude.The internal pressure restricted the ratcheting accumulation in the axial direction,but promoted the hoop ratcheting strain on the contrary.In addition,the loading history and loading sequence had significant influences on multiaxial ratcheting strain.The microstructure observations illustrated that no significant difference of textures between the as-received tubes and the deformed tubes,which indicated that the textures of zirconium alloy tubes cannot be significantly changed by the limited ratcheting deformation.