【摘要】：在現(xiàn)代工業(yè)中,高溫、高壓設(shè)備應(yīng)用的日益廣泛以及其逐漸向更高溫度、更大壓力方向發(fā)展的趨勢迫使人們快速開發(fā)新的可適用材料,同時(shí)也使人們更為關(guān)注服役材料的安全性。持久性能是保證材料安全服役的重要指標(biāo),通常采用蠕變持久實(shí)驗(yàn)的方法來獲得,但是該方法存在著周期長、材料需要量大、能耗高等缺點(diǎn),制約著人們對材料蠕變性能的快速認(rèn)知,進(jìn)而降低新材料的研發(fā)速度。因此,迫切需要一種快速且準(zhǔn)確的持久性能預(yù)測方法。應(yīng)力松弛實(shí)驗(yàn)作為一種蠕變信息的快速獲得方法,可以用于快速的分析材料的蠕變持久性能�；诖�,本文以具有典型BCC和FCC晶體結(jié)構(gòu)的數(shù)種耐熱鋼材料為研究對象,分別開展了應(yīng)力松弛實(shí)驗(yàn)和蠕變持久實(shí)驗(yàn),探討了應(yīng)力松弛過程中的蠕變速率(稱為松弛蠕變速率,εSRT)與恒載荷蠕變的最小蠕變速率εmin)的關(guān)系及相關(guān)因素的影響作用,分析了穩(wěn)態(tài)松弛蠕變和穩(wěn)態(tài)恒載荷蠕變的變形機(jī)制,并提出了基于材料的應(yīng)力松弛行為快速且高精度的預(yù)測持久性能的方法。研究發(fā)現(xiàn),材料的松弛蠕變速率與最小蠕變速率的大小關(guān)系較為復(fù)雜,受材料、溫度(T)和應(yīng)力(σ)等因素影響作用較大。其中,材料因素的影響作用主要在于兩種穩(wěn)態(tài)蠕變階段的微觀組織差異,與材料晶體結(jié)構(gòu)類型關(guān)系不大；當(dāng)溫度條件為T/Tm≥0.60且應(yīng)力條件為σ/σ0.2≤0.40時(shí),不同材料都表現(xiàn)出εmin與穩(wěn)態(tài)εSRT大小相接近現(xiàn)象,超出這個(gè)條件范圍的εmin與穩(wěn)態(tài)εSRT大小關(guān)系則較為復(fù)雜。與此同時(shí),本文也提出了穩(wěn)態(tài)松弛蠕變速率與最小蠕變速率的相互轉(zhuǎn)化模型,并在多種材料中得到了驗(yàn)證。通過分析數(shù)種材料在穩(wěn)態(tài)松弛蠕變階段和穩(wěn)態(tài)恒載荷蠕變階段的應(yīng)力指數(shù)、表觀激活能和表觀激活體積的大小,本文認(rèn)為：εmin與穩(wěn)態(tài)εSRT大小相近現(xiàn)象的產(chǎn)生與冪律失效蠕變無關(guān),而與位錯(cuò)攀移、粘滯性滑移和擴(kuò)散蠕變等應(yīng)力指數(shù)較低的冪律蠕變有關(guān)；穩(wěn)態(tài)松弛蠕變過程中表觀激活體積隨應(yīng)力降低而增大的現(xiàn)象表明低應(yīng)力的穩(wěn)態(tài)松弛蠕變行為對熱激活運(yùn)動(dòng)依賴性較強(qiáng)。另外,Tm為熔點(diǎn)絕對溫度,σ0.2為發(fā)生0.2%塑性應(yīng)變時(shí)的屈服應(yīng)力。在預(yù)測持久性能方面,傳統(tǒng)的基于蠕變持久實(shí)驗(yàn)的斷裂時(shí)間數(shù)據(jù)和最小蠕變速率數(shù)據(jù)的方法在預(yù)測結(jié)果上相差不大,但是僅采用時(shí)間相對較短的蠕變持久實(shí)驗(yàn)數(shù)據(jù)來預(yù)測的持久性能可能與真實(shí)蠕變數(shù)據(jù)差異較大,這意味著傳統(tǒng)方法在高精度預(yù)測材料持久性能時(shí)較為依賴于長時(shí)間的蠕變持久實(shí)驗(yàn)數(shù)據(jù)。而通過應(yīng)力松弛實(shí)驗(yàn)數(shù)據(jù)結(jié)合少量的高應(yīng)力蠕變持久實(shí)驗(yàn)數(shù)據(jù)的方法可以高精度的預(yù)測材料的持久性能,其預(yù)測結(jié)果比僅采用短時(shí)間蠕變持久實(shí)驗(yàn)的傳統(tǒng)預(yù)測方法具有更高的精度,并且與真實(shí)蠕變數(shù)據(jù)相差不大。
[Abstract]:In modern industry, the increasing application of high-temperature and high-pressure equipment and its trend towards higher temperature and greater pressure force people to develop new and applicable materials quickly. It also makes people pay more attention to the safety of service materials. The durability property is an important index to ensure the safe service of materials, which is usually obtained by creep rupture test. However, this method has many disadvantages, such as long period, large material requirement, high energy consumption, and so on. It restricts the rapid understanding of creep properties of materials, and then reduces the speed of research and development of new materials. Therefore, there is an urgent need for a fast and accurate durable performance prediction method. As a fast method to obtain creep information, stress relaxation test can be used to analyze the creep rupture properties of materials. Based on this, stress relaxation experiments and creep rupture tests were carried out on several heat-resistant steel materials with typical BCC and FCC crystal structures, respectively. The relationship between creep rate (called relaxation creep rate, 蔚 SRT) and minimum creep rate 蔚 min (constant load creep) and the influence of relative factors on creep rate during stress relaxation are discussed. The deformation mechanism of steady relaxation creep and steady state constant load creep is analyzed. A fast and high precision method for predicting the rupture performance based on the stress relaxation behavior of materials is proposed. It is found that the relationship between the relaxation creep rate and the minimum creep rate is more complex, which is influenced by the factors such as material, temperature (T) and stress (蟽). Among them, the effect of material factors is mainly due to the difference of microstructure between the two steady state creep stages, and has little relation to the crystal structure type of the material, when the temperature condition is T/Tm 鈮，

本文編號(hào)：2195818