Transformation Temperature of Titanium Measured by DSC AITranslate
Abstract AITranslate
β transus temperature （Tβ） is a very important process parameter. Due to the fluctuation of composition and different content of interstitial elements，the phase transformation temperature of titanium alloy products of the same brand and different batches can have a deviation of tens of degrees. In order to ensure the quality stability of materials，β phase transformation temperature of each batch of titanium materials is measured in industrial production. At present，Thermal analysis method and metallographic method are commonly used for measuring the transformation point of titanium alloy. In this paper，it was measured by differential scanning calorimetry for β transformation temperature of α-type，α+β-type and metastable β-type titanium alloys to analyze the applicability of transition temperature in differential scanning calorimetry （DSC）. The microstructure of the sample was observed and analyzed by metallographic microscope during DSC measurement process，the influence mechanism of phase transformation，room temperature and high temperature microstructure of titanium alloy on DSC measurement data was studied. The effect of heating rate on DSC results of TC4 sample was studied to observe the optimal DSC parameter. At the same time，in order to determine the accuracy of DSC method in measuring the transformation point temperature of titanium and titanium alloy，the metallographic method was used for data comparison and analysis. The results showed that DSC could be used to measure β phase transformation point of various types of titanium alloys. According to metastable β-type titanium，especially in hot working state or solid solution state，there was no obvious endothermic/exothermic peak in DSC curve，it was suggested that β titanium alloys could be heat treated in 650 ℃/1 h +550 ℃/1 h air cooling （AC） before DSC measurement to ensure sufficient α phase precipitation. For forging α+β-type titanium alloy，due to the difference and transformation of titanium alloy microstructure during DSC heating and cooling，there was a large deviation between the first measurement and the subsequent measurement results. The original state of TC4 was hot working state，the original α phase was broken or disintegrated，the initial crystallographic relationship between α and β phase was destroyed，the microstructure was equiaxed α phase + intergranular β. When it was heated to β phase，the phase transformation needed to overcome large resistance. Due to no holding time in the heating process of DSC method，Tβ moved to high temperature. After cooling from 1120 ℃，α and β phases followed the burgers orientation relationship：（110）β∥（0001）α，［111］β∥［1120］α，the microstructure was primitive β grain boundary + fine lamellar β transformation structure. On the second repeated temperature rise，α→β transition proceeded inversely along the habitual surface during cooling，the phase transition resistance was greatly reduced and Tβ was close to the real phase transition temperature. After the third DSC test，the microstructure was no longer changed and remained original β grain boundary + fine lamellar β. It could be seen that the results of phase transformation point of titanium after the first time were the actual phase transformation temperature for forging α+β，usually the second result could be used as the final Tβ. The phase transition point temperatures were 989 ℃ （10 ℃·min−1），989 ℃ （20 ℃·min−1） and 996 ℃ （30 ℃·min−1） respectively. When the heating rate was 10 ℃·min−1，the phase transition endothermic peak was very flat，the peak shape was small，and the thermal effect was not obvious. When the heating rate increased to 20 and 30 ℃·min−1，the phase transition reaction peak was obvious，the peak shape was sharp，and the sensitivity was improved. The measured value of 20 ℃·min−1 was roughly consistent with that of 10 ℃·min−1，and the phase transition point temperature of 30 ℃·min−1 was relatively high. During DSC test，the heating rate was directly proportional to the thermal hysteresis effect of the sample. The larger the heating rate，the more serious the thermal hysteresis phenomenon was. The slower the heating rate was，the smaller the thermal hysteresis effect was，the higher the resolution was，but the sensitivity was reduced. So，based on the above data and reasons，it was suggested that the heating rate should be measured at 20 ℃·min−1 for TC4 by DSC. The metallographic method was used to verify the accuracy of DSC measurement，it showed that the phase transition point data of differential scanning calorimetry and metallography β were very close，the difference was only 7 ℃. Due to the characteristics of low thermal conductivity of titanium alloy and fast heating rate，there was not enough time for the complete phase transition reaction，resulting the thermal lag effect during DSC measurement and the results difference between the differential scanning calorimetry and metallographic. Therefore，DSC measurement results were relatively reliable. After temperature correction，DSC method could be used as a fast and reliable means for phase transition point temperature measurement.
KeyWords AITranslate
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Basic Information:
DOI：10.13373/j.cnki.cjrm.XY22030033
Chinese Library Classification Number:TG146
Citation Information:
β transus temperature （Tβ） is a very important process parameter. Due to the fluctuation of composition and different content of interstitial elements，the phase transformation temperature of titanium alloy products of the same brand and different batches can have a deviation of tens of degrees. In order to ensure the quality stability of materials，β phase transformation temperature of each batch of titanium materials is measured in industrial production. At present，Thermal analysis method and metallographic method are commonly used for measuring the transformation point of titanium alloy. In this paper，it was measured by differential scanning calorimetry for β transformation temperature of α-type，α+β-type and metastable β-type titanium alloys to analyze the applicability of transition temperature in differential scanning calorimetry （DSC）. The microstructure of the sample was observed and analyzed by metallographic microscope during DSC measurement process，the influence mechanism of phase transformation，room temperature and high temperature microstructure of titanium alloy on DSC measurement data was studied. The effect of heating rate on DSC results of TC4 sample was studied to observe the optimal DSC parameter. At the same time，in order to determine the accuracy of DSC method in measuring the transformation point temperature of titanium and titanium alloy，the metallographic method was used for data comparison and analysis. The results showed that DSC could be used to measure β phase transformation point of various types of titanium alloys. According to metastable β-type titanium，especially in hot working state or solid solution state，there was no obvious endothermic/exothermic peak in DSC curve，it was suggested that β titanium alloys could be heat treated in 650 ℃/1 h +550 ℃/1 h air cooling （AC） before DSC measurement to ensure sufficient α phase precipitation. For forging α+β-type titanium alloy，due to the difference and transformation of titanium alloy microstructure during DSC heating and cooling，there was a large deviation between the first measurement and the subsequent measurement results. The original state of TC4 was hot working state，the original α phase was broken or disintegrated，the initial crystallographic relationship between α and β phase was destroyed，the microstructure was equiaxed α phase + intergranular β. When it was heated to β phase，the phase transformation needed to overcome large resistance. Due to no holding time in the heating process of DSC method，Tβ moved to high temperature. After cooling from 1120 ℃，α and β phases followed the burgers orientation relationship：（110）β∥（0001）α，［111］β∥［1120］α，the microstructure was primitive β grain boundary + fine lamellar β transformation structure. On the second repeated temperature rise，α→β transition proceeded inversely along the habitual surface during cooling，the phase transition resistance was greatly reduced and Tβ was close to the real phase transition temperature. After the third DSC test，the microstructure was no longer changed and remained original β grain boundary + fine lamellar β. It could be seen that the results of phase transformation point of titanium after the first time were the actual phase transformation temperature for forging α+β，usually the second result could be used as the final Tβ. The phase transition point temperatures were 989 ℃ （10 ℃·min−1），989 ℃ （20 ℃·min−1） and 996 ℃ （30 ℃·min−1） respectively. When the heating rate was 10 ℃·min−1，the phase transition endothermic peak was very flat，the peak shape was small，and the thermal effect was not obvious. When the heating rate increased to 20 and 30 ℃·min−1，the phase transition reaction peak was obvious，the peak shape was sharp，and the sensitivity was improved. The measured value of 20 ℃·min−1 was roughly consistent with that of 10 ℃·min−1，and the phase transition point temperature of 30 ℃·min−1 was relatively high. During DSC test，the heating rate was directly proportional to the thermal hysteresis effect of the sample. The larger the heating rate，the more serious the thermal hysteresis phenomenon was. The slower the heating rate was，the smaller the thermal hysteresis effect was，the higher the resolution was，but the sensitivity was reduced. So，based on the above data and reasons，it was suggested that the heating rate should be measured at 20 ℃·min−1 for TC4 by DSC. The metallographic method was used to verify the accuracy of DSC measurement，it showed that the phase transition point data of differential scanning calorimetry and metallography β were very close，the difference was only 7 ℃. Due to the characteristics of low thermal conductivity of titanium alloy and fast heating rate，there was not enough time for the complete phase transition reaction，resulting the thermal lag effect during DSC measurement and the results difference between the differential scanning calorimetry and metallographic. Therefore，DSC measurement results were relatively reliable. After temperature correction，DSC method could be used as a fast and reliable means for phase transition point temperature measurement.
quote
| GB/T 7714-2015 | [1] Hongju Zhang, Ronggui Guo, Donghui Zhang, et al. Transformation Temperature of Titanium Measured by DSC[J]. Chinese Journal of Rare Metals, 2024, 48(10): 1388-1395. DOI:10.13373/j.cnki.cjrm.XY22030033. |
| MLA | [1] Hongju Zhang, et al., "Transformation Temperature of Titanium Measured by DSC." Chinese Journal of Rare Metals, vol. 48, no. 10, 2024, pp. 1388-1395, https://doi.org/10.13373/j.cnki.cjrm.XY22030033. |
| APA | [1] Hongju Zhang, Ronggui Guo, Donghui Zhang, Wen Xia, Shufeng Liu, Yingbao Zhong, & Shuming Wang. (2024). Transformation Temperature of Titanium Measured by DSC. Chinese Journal of Rare Metals, 48(10), 1388-1395. https://doi.org/10.13373/j.cnki.cjrm.XY22030033 |
| IEEE | [1] Hongju Zhang, Ronggui Guo, Donghui Zhang, Wen Xia, Shufeng Liu, Yingbao Zhong, and Shuming Wang, "Transformation Temperature of Titanium Measured by DSC," Chinese Journal of Rare Metals, vol. 48, no. 10, pp. 1388-1395, 2024, doi: 10.13373/j.cnki.cjrm.XY22030033. keywords: {transmission point；;microstructure；;metallography；;differential scanning calormetry （DSC）} |