Abstract
The competitive effect of microstructural features including primary α(αp),secondary α(αs),grain boundary α(αGB)and β grain size on mechanical properties of a near β Ti alloy were studied with two heat treatment processes.The relative effect of β grain size and STA(solution treatment and ageing)pro-cessing parameters on mechanical properties were quantitatively explored by the application of Taguchi method.These results were further explained via correlating microstructure with the fracture toughness and tensile properties.It was found that large numbers of fine αs precipitates and continuous αGB played greater roles than other features,resulting in a high strength and very low ductility(＜2％)of STA process samples.The β grain size had a negative correlation with fracture toughness.In the samples prepared by BASCA(β anneal slow cooling and ageing)process,improved ductility and fracture toughness were ob-tained due to a lower density of αs precipitates,a basket-weave structure and zigzag morphology of αGB.For this heat treatment,an increase in prior β grain size had an observable positive effect on fracture toughness.The contradictory effect of β grain size on fracture toughness found in literature was for the first time explained.It was shown that the microstructure obtained from different processes after β solu-tion has complex effect on mechanical properties.This complexity derived from the competition between microstructure features and the overall sum of their effect on fracture toughness and tensile properties.A novel table was proposed to quasi-quantitatively unravel these competitive effects.
基金项目
Baosteel Australia Joint Research Centre(BA16003)
ARC Research Hub for Computational Particle Technology(IH140100035)
a Node of Microscopy Australia,particularly the electron microscope funded by Australian Research Council(LE0882821)
NETL
NSTL
维普
万方数据