【作者】 王伟功；

【导师】 孙东立；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2006， 硕士

【摘要】 本文对含氢BT20合金的高温热压缩行为及变形机理进行了研究。测定了渗氢时间和氢含量之间的关系,使用Gleeble-1500D热模拟试验机得到了含氢BT20合金热压缩真应力-真应变曲线,讨论了不同工艺参数不同变形条件下真应力-真应变曲线的变化规律。利用金相显微镜、透射电子显微镜(TEM)和高分辨电子显微镜(HREM)观察了压缩变形前后的微观组织,计算了不同温度下的变形激活能,讨论了热变形行为及变形机理。对真空除氢工艺进行了初步探索。渗氢结果表明,氢气流量为990ml/min,分压为0.1MPa,800℃下渗氢,渗氢时间和氢含量之间的关系为:CH(t)=1.2-1.2exp(-t/120),固、气界面的扩散通量为:J=3ρ[exp(-t/120)]/200。TEM观察结果表明,达到一定的氢浓度后生成氢化物,直到氢质量百分含量为0.76%室温得到的依然是面心立方的δ氢化物,氢化物特征是针状浮凸,具有惯习面和中脊。含氢BT20合金热压缩变形的流变应力曲线随着氢含量的增加先下移再升高。适当的氢含量可以使流变应力峰值达到最小值。应变速率会影响最低流变应力峰值对应的氢含量。计算得到氢含量为0.47%的BT20合金600℃/8.3×10-4s-1变形激活能为90KJ·mol-1,比原始材料600℃的变形激活能降低了50KJ·mol-1。原始材料800℃的变形激活能为390KJ·mol-1。氢含量为0.47%的BT20合金800℃/8.3×10-4s-1变形激活能为140KJ·mol-1,变形方式发生了变化。TEM和HREM观察结果表明,600℃变形出现层错和孪晶。800℃高应变速率时变形发生再结晶。氢含量为0.47%的BT20合金变形前后的除氢结果表明,渗氢后适当的变形速率使α相晶粒变形时,除氢获得的晶粒比较细小。更多还原

【Abstract】 The thermo-compressive behavior and deformation mechanism of BT20 alloy with hydrogen at high temperature were studied in this paper. Relation of hydrided time and hydrogen content was mensurated. Ture stress-ture strain curve of thermo-compressive deformation of BT20 alloy with hydrogen was obstained by Gleeble-1500D and different process parameter effect on it was discussed. Metallomicroscope (MS), transmission electron microscope (TEM) and high resolution electron microscope (HREM) were used to observe microstructure before and after thermo-compressive deformation. Activation energy of deformation was calculated.Deformation behavior and mechanism was discussed by activation energy of deformation and microstructure.Dehydrided process in vacuum was investigated.The hydrided results show relation of hydrided time and hydrogen content meets CH(t)=1.2-1.2exp(-t/120), diffusion flux of solid and gas interface J= 3ρ[exp(-t/120)]/200 with hydrogen partial pressure 0.1MPa and hydrogen flux 990ml?min-1. TEM shows only hydrides were generated until hydrogen content up to 0.76% and hydrides have features as follows: needle convex, habit plane, median ridge, bit vector.Ture stress-ture strain curve of thermo-compressive deformation of BT20 alloy with hydrogen first descends and then rises integrally as hydrogen content increases and peak of flow stress occur in it. Appropriate hydrogen content can reduce peak of flow stress up to minimal value. Strain rate effect on hydrogen content corresponding to minimal value of peak of flow stress.Activation energy of deformation of BT20 alloy with 0.47% hydrogen content and strain rate 8.3×10-4s-1 is 90KJ·mol-1. Hydrogen reduces Activation energy of deformation in 600℃by 50 KJ·mol-1. Activation energy of deformation of BT20 alloy in 800℃is 390KJ·mol-1, Activation energy of deformation of BT20 alloy with 0.47% hydrogen content in 800℃and strain rate 8.3×10-4s-1 is 140KJ·mol-1. MS, TEM and HREM show fault ribbon and twin after deformation.recrystallization occurs in high strain rate in 800℃.Dehydrided result of before and after deformation of BT20 alloy with 0.47%更多还原