The effects of cooling rates on solidification behaviors,segregation characteristics and tensile property of GH4151 alloy were investigated using microstructure characterization and tensile test.Firstly,a relationship...The effects of cooling rates on solidification behaviors,segregation characteristics and tensile property of GH4151 alloy were investigated using microstructure characterization and tensile test.Firstly,a relationship between the secondary dendrite arm spacing and cooling rate was determined and it was confirmed to be valid.Secondly,it can be found from microstructure observations that the morphology of(Nb,Ti)C carbides transits from blocky and script type to fine script type and spotty type,and the refinedγ'phase was observed due to decrease of segregation with increasing cooling rates.Thirdly,the solidification microstructures of the industrial-scale samples were analyzed.The morphology ofηphase changes from indistinguishable shape,fine needle-like shape to large block-like shape with increasing ingot diameter.As a result,the mechanical properties of alloy decrease due to increase of brittle precipitations.The experimental results show that the precipitation behavior of GH4151 is affected by segregation degree of elements,and the segregation degree is determined by solute distribution process and solid back-diffusion process.展开更多
使用高温同步热分析仪,以10 K/min的升温速率对55%CaF2-20%CaO-3%MgO-22%Al2O3-x%B2O3(质量分数,x≤3.0)的失重率进行测定.根据测定结果确定挥发反应机理函数G(α)和动力学参数,并分析挥发反应机理.结果表明:随B2O3加入量增加,熔渣挥发...使用高温同步热分析仪,以10 K/min的升温速率对55%CaF2-20%CaO-3%MgO-22%Al2O3-x%B2O3(质量分数,x≤3.0)的失重率进行测定.根据测定结果确定挥发反应机理函数G(α)和动力学参数,并分析挥发反应机理.结果表明:随B2O3加入量增加,熔渣挥发失重量降低;温度≥1 673 K时,熔渣挥发机理函数为G(α)=α,符合Mampel power law (n=1),熔渣挥发受挥发组元的形核长大控制;加入质量分数0.5%B2O3使熔渣挥发活化能从458.69 kJ·mol^-1降低至431.54 kJ·mol^-1,但B2O3加入量≥1.0%,活化能变化不明显;B2O3加入可抑制熔渣吸潮,为降低熔渣烘烤成本,熔渣中B2O3加入量应≥1.0%;提高炉内CaF2分压,可大幅降低熔渣的挥发失重及熔渣挥发对冶炼铸锭质量的影响.展开更多
文摘The effects of cooling rates on solidification behaviors,segregation characteristics and tensile property of GH4151 alloy were investigated using microstructure characterization and tensile test.Firstly,a relationship between the secondary dendrite arm spacing and cooling rate was determined and it was confirmed to be valid.Secondly,it can be found from microstructure observations that the morphology of(Nb,Ti)C carbides transits from blocky and script type to fine script type and spotty type,and the refinedγ'phase was observed due to decrease of segregation with increasing cooling rates.Thirdly,the solidification microstructures of the industrial-scale samples were analyzed.The morphology ofηphase changes from indistinguishable shape,fine needle-like shape to large block-like shape with increasing ingot diameter.As a result,the mechanical properties of alloy decrease due to increase of brittle precipitations.The experimental results show that the precipitation behavior of GH4151 is affected by segregation degree of elements,and the segregation degree is determined by solute distribution process and solid back-diffusion process.
文摘使用高温同步热分析仪,以10 K/min的升温速率对55%CaF2-20%CaO-3%MgO-22%Al2O3-x%B2O3(质量分数,x≤3.0)的失重率进行测定.根据测定结果确定挥发反应机理函数G(α)和动力学参数,并分析挥发反应机理.结果表明:随B2O3加入量增加,熔渣挥发失重量降低;温度≥1 673 K时,熔渣挥发机理函数为G(α)=α,符合Mampel power law (n=1),熔渣挥发受挥发组元的形核长大控制;加入质量分数0.5%B2O3使熔渣挥发活化能从458.69 kJ·mol^-1降低至431.54 kJ·mol^-1,但B2O3加入量≥1.0%,活化能变化不明显;B2O3加入可抑制熔渣吸潮,为降低熔渣烘烤成本,熔渣中B2O3加入量应≥1.0%;提高炉内CaF2分压,可大幅降低熔渣的挥发失重及熔渣挥发对冶炼铸锭质量的影响.
