本文關鍵詞：GH4169合金中δ相對疲勞性能的影響規(guī)律研究　出處：《貴州大學》2016年碩士論文　論文類型：學位論文

  更多相關文章： GH4169合金 δ相 斷裂韌性 疲勞裂紋擴展速率

【摘要】：GH4169合金是一種時效強化型高溫合金,由于其良好的強韌性,耐蝕性,焊接性能及抗疲勞性能,在航空航天和石油行業(yè)得到廣泛的運用。合金中析出相δ相的析出、溶解規(guī)律及其熱加工行為已得到廣泛的研究。外在環(huán)境因素、加載條件對GH4169合金疲勞裂紋擴展速率的影響規(guī)律也有報道。然而δ相含量對GH4169合金斷裂韌性及疲勞裂紋擴展速率的研究卻鮮有報道。本文通過定量表征δ相的含量對GH4169合金疲勞裂紋擴展及斷裂性能。采用OM、SEM、TEM等技術手段表征GH4169合金顯微組織及δ相的體積分數(shù)。研究不同的δ相含量和晶粒尺寸對GH4169合金斷裂韌性和疲勞裂紋擴展速率的影響機制。本文研究這六種熱處理工藝中,δ相含量隨著固溶溫度的下降及保溫時間的延長而增加。隨著δ相的增加,材料的強度降低,但是塑性卻有所增加。隨著晶粒尺寸的增加,材料強度下降,符合霍爾佩奇關系。材料的沖擊韌性隨著δ相的增加而降低。隨著δ相含量的增加,GH4169合金斷裂韌度呈現(xiàn)下降的趨勢。δ相主要沿晶界分布。由于δ相本身為金屬間化合物,且其周圍會形成貧Nb元素的微塑性區(qū),對裂紋擴展有吸引作用,從而導致裂紋發(fā)生沿晶擴展。晶粒尺寸增大會降低裂紋遇到晶界的概率,在一定的晶粒尺寸范圍內增加裂紋的擴展阻力,提高材料的斷裂韌度。通過緊湊拉伸試樣得到六種工藝狀態(tài)下GH4169合金的Paris曲線。結果表明,δ相含量的增加會導致Paris曲線的穩(wěn)定擴展階段和快速擴展階段的疲勞裂紋擴展速率增加。穩(wěn)定擴展階段裂紋尖端塑性區(qū)大于等于晶粒尺寸,分布在晶界上的δ相會加速疲勞裂紋擴展速率。在快速擴展階段,裂紋尖端塑性區(qū)遠大于晶粒尺寸,δ相對疲勞裂紋擴展的影響作用更加顯著。在低應力強度因子狀態(tài)下,接近于Paris曲線的初始擴展階段時,裂紋尖端塑性區(qū)小于晶粒尺寸,δ相對疲勞裂紋擴展速率的影響效果降低。在這個階段,一定的晶粒尺寸條件的,適當?shù)脑黾泳Я３叽缬兄诮档推诹鸭y擴展速率。
[Abstract]:GH4169 alloy is a kind of aging strengthened superalloy, because of its good strength and toughness, corrosion resistance, welding property and fatigue resistance. It has been widely used in aerospace and petroleum industry. The precipitation, dissolution and hot working behavior of 未 phase in alloy have been widely studied. The effect of loading conditions on the fatigue crack growth rate of GH4169 alloy is also reported. However, the study of 未 phase content on fracture toughness and fatigue crack growth rate of GH4169 alloy is rarely reported. The fatigue crack propagation and fracture properties of GH4169 alloy were quantitatively characterized by the content of 未 phase. OM was used. SEM. TEM and other techniques were used to characterize the microstructure and volume fraction of 未 phase in GH4169 alloy. The effects of 未 phase content and grain size on fracture toughness and fatigue crack propagation rate of GH4169 alloy were studied. Mechanism. In this paper, six kinds of heat treatment processes are studied. The content of 未 phase increases with the decrease of solution temperature and the prolongation of holding time. With the increase of 未 phase, the strength of the material decreases, but the plasticity increases. With the increase of grain size, the strength of the material decreases. The impact toughness of the material decreases with the increase of 未 phase and increases with the increase of 未 phase content. The fracture toughness of GH4169 alloy shows a decreasing trend. 未 phase mainly distributes along grain boundary. Because 未 phase itself is an intermetallic compound, and there is a microplastic zone around it, which is poor in NB element. The increase of grain size will reduce the probability of crack meeting grain boundary and increase the resistance of crack propagation in a certain range of grain size. The Paris curves of GH4169 alloy under six different processing conditions were obtained by compact tensile test. The results showed that the fracture toughness of the alloy was improved. The increase of 未 phase content leads to the increase of fatigue crack growth rate in the stable and fast growth stages of the Paris curve, and the plastic zone at the crack tip is greater than or equal to the grain size in the stable growth stage. The 未 phase distributed on the grain boundary will accelerate the fatigue crack growth rate. At the rapid growth stage, the plastic zone at the crack tip is much larger than the grain size. The effect of 未 on fatigue crack growth is more obvious. At the condition of low stress intensity factor, the plastic zone at crack tip is smaller than grain size when it is close to the initial growth stage of Paris curve. The effect of 未 on fatigue crack growth rate is reduced. At this stage, a proper increase of grain size is helpful to reduce the fatigue crack growth rate under certain grain size conditions.
【學位授予單位】：貴州大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TG132.3

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