【作者】 段春艳；

【导师】 郭鸿镇；

【作者基本信息】 西北工业大学 ， 材料加工工程， 2004， 硕士

【摘要】 钛合金、铝合金等有色合金强度高、重量轻，被广泛应用在结构重量有至关重要意义的航空航天制造业中。研究这些合金的超塑性能，对采用超塑性等温锻造方法制造复杂形状锻件具有重要意义。 本文对Φ16mmLD10铝合金热轧棒材采用420℃再结晶退火处理，使合金获得更加均匀、细小的晶粒组织，平均延伸率由158.2％提高到223％，该方案为本文推荐的较佳超塑性预处理方案。另外，原棒材经380℃、460℃退火及500℃固溶水冷处理后，也可获得较细的晶粒和较好的超塑性，个别试样的延伸率高达321％。 超塑性拉伸试验结果表明，经420℃退火处理后，LD10铝合金在460℃～510℃温度范围内，及在1.1×10^-2S^-1～1.1×10^-4S^-1应变速率范围内，具有超塑性，平均延伸率在108％～231％范围内变化。本文所得的最佳超塑性温度范围为500℃～510℃，最佳应变速率为3.3×10^-4S^-1，在此温度和应变速率条件下，经420℃退火处理棒材的平均延伸率达到223％～231％，流动应力仅为10.389MPa～12.962MPa。在具有较好超塑性的LD10拉伸断口中，于晶粒表面上产生有大量的丝状金属须。 本文以具有明显铁偏析的Ti-1023合金棒材为原材料，采用粉末烧结+等温锻造的复合工艺制备Ti-1023粉末合金，使合金相对密度高达99.57％，显微组织异常均匀、细小，初生α相等轴性良好，完全消除了原棒材中的Fe偏析和β斑缺陷，室温拉伸性能大幅度提高，并呈现出了1269％的良好超塑性，个别试样δ值高达1422％，该项复合工艺为制备优质Ti-1023合金、细化合金组织、提高超塑性能的有效方法。 超塑性拉伸试验结果表明，Ti-1023粉末合金在700℃～820℃温度范围内以及在3.3×10^-4s^-1～3.3×10^-2S^-1应变速率范围内都具有超塑性，拉伸延伸率分别在391％～1269％和155％～1422％范围内显著变化。所得最佳超塑性温度为750℃～760℃，最佳初始应变速率为3.3×10^-4s^-1～3.3×10^-3s^-1，在此温度和初始应变速率条件下，延伸率高达1269％～1422％，流动应力仅为23.6 MPa～62.3MPa。在最佳超塑性条件下Ti-1023粉末合金拉伸试样呈现典型的“点”形式断裂，断口表面起伏很大，晶间断裂特征特别明显。更多还原

【Abstract】 Titanium and aluminum alloys, which are nonferrous alloys, have considerable strength-to-weight advantage over comparable-strength steels. Therefore, they have been found in wide use in aerospace industry. It is of great significance to research on the superplastic properties of these alloys for using superplastic isothermal forging to manufacture complex forge pieces.In this paper, equiaxed fine-grained structure can be obtained when 16mm diameter hot-rolled bars of LD10 alloy are pretreated via proper recrystallization annealing (temperature 420℃). The average elongation is increased from 158.2% to 223%, and the process is the optimal pretreatment in this paper. In addition, equiaxed fine-grained structure and better superplasticity can also be obtained when the hot-rolled bars are pretreated via proper recrystallization annealing (temperature 380℃, 460℃) and solution annealing (temperature 500℃). And the maximum elongation is 321% in individual specimen.The tensile specimens through annealing at 420℃ present superplasticity (elongation 108%~231%), in the range of temperature from 460℃ to 510℃ and the strain rate from 1.1x10-2s-1 to 1.1x10-4s-1. The optimal superplastic deformation condition is 500℃~510℃ and 3.3x10-4s-1, on which the average elongation is 223%~232% and the flow stress is only 10.389MPa~12.962MPa. The tensile specimens which show better superplasticity appear filaments fracture.The process of powder sintering + isothermal forging is used for Ti-1023 alloy in which the element of Fe is segregated obviously. The relative density can reach 99.57%, homogeneous and fine-grained microstructure can be obtained, the primary a phases are better equiaxed grain and Fe segregation and B spot are completely removed. The tensile property at room temperature get better improved. Therefore the alloy presents excellent superplasticity (elongation 1269%), and the maximum value in individual specimen is 1422%. The process is an effective way to prepare high quality Ti-1023 alloy, to refine the microstructure and improve the superplastic property of the alloy.The experimental result of superplastic tensile test indicates that Ti-1023 powder alloy appear superplasticity (elongation 391%~1269% and 155%~1422% ) in the range of temperature from 700℃ to 820℃ and strain rate from 3.3 X10-4s-1to 3.3 X 10-2s-1. The optimal superplastic deformation condition is 750℃~760℃ and 3.3 X 10-4s-1-3.3 X 10-3s-1, in which the elongation can reach 1269%~1422% and the flowstress is 23.6Mpa~62.3 Mpa. Under optimal superplastic deformation condition the tensile specimens fracture in the form of point and the fracture surface fluctuates greatly. It shows obvious intergranular fracture.更多还原