Here,a near alpha-type Ti6.5 Al2 Zr1 Mo1 V alloy has been fabricated by electron beam selective melting(EBSM).Near-equiaxed grains existed in the first few layers,whereas elongated columnar priorβgrains almost parall...Here,a near alpha-type Ti6.5 Al2 Zr1 Mo1 V alloy has been fabricated by electron beam selective melting(EBSM).Near-equiaxed grains existed in the first few layers,whereas elongated columnar priorβgrains almost parallel to the building direction formed in the subsequent built layers.Interspacing ofβphase gradually decreased as the build height increased.Martensiteα'with twins and dislocations emerged and microhardness value reached the maximum in the top region,whereas onlyα/βphase appeared in other regions in the EBSMed sample.Multiple phase transformations can be observed with the change of peak temperatures during each thermal cycle.With a sufficient dwell time,martensiteα'in the middle and bottom regions in-situ decomposed intoα+βand coarsened by the heat conduction from the subsequent layers.Fineβprecipitates nucleated heterogeneously insideα'plates and at plate-plate interfaces during the subsequent EBSM process.Considering the phase transformation during the heating process and the cooling process,the existence time of different phases was combined with cycle heating and cooling to clarify the dynamic evolution of micro structure under complex thermal history of EBSM,favoring the fabrication of high-performance titanium alloy components.展开更多
基金financial support from The National Key Research and Development Program of China(2018YFB1105200)。
文摘Here,a near alpha-type Ti6.5 Al2 Zr1 Mo1 V alloy has been fabricated by electron beam selective melting(EBSM).Near-equiaxed grains existed in the first few layers,whereas elongated columnar priorβgrains almost parallel to the building direction formed in the subsequent built layers.Interspacing ofβphase gradually decreased as the build height increased.Martensiteα'with twins and dislocations emerged and microhardness value reached the maximum in the top region,whereas onlyα/βphase appeared in other regions in the EBSMed sample.Multiple phase transformations can be observed with the change of peak temperatures during each thermal cycle.With a sufficient dwell time,martensiteα'in the middle and bottom regions in-situ decomposed intoα+βand coarsened by the heat conduction from the subsequent layers.Fineβprecipitates nucleated heterogeneously insideα'plates and at plate-plate interfaces during the subsequent EBSM process.Considering the phase transformation during the heating process and the cooling process,the existence time of different phases was combined with cycle heating and cooling to clarify the dynamic evolution of micro structure under complex thermal history of EBSM,favoring the fabrication of high-performance titanium alloy components.
