冶炼工艺对A286合金高温拉伸性能的影响

为了研究冶炼工艺对A286合金高温拉伸性能的影响，分别采用真空感应熔炼炉+电渣重熔和电弧炉+VOD炉+LF炉+电渣重熔两种工艺冶炼了不同成分的A286合金。对合金进行了900℃保温2 h水冷的固溶处理和720℃保温16 h的时效处理，并在450、550、650、700、750、800℃进行了拉伸试验。结果表明：固溶和时效处理后采用两种工艺冶炼的A286合金的显微组织均为奥氏体，并有孪晶，晶粒度为9.5级；随着拉伸试验温度的提高，合金的屈服和抗拉强度均降低；由于孪晶和晶界析出相较多，电弧炉熔炼试样的高温强度略高于真空感应熔炼试样；由于杂质含量较高，电弧炉熔炼试样在650～700℃发生脆断，700℃塑性最低。     

三联冶炼IN718合金棒材650℃长期时效后的组织与性能

研究了经标准热处理的真空感应+电渣重熔+真空自耗三联工艺冶炼IN718合金细晶250 mm棒材在650℃下长期时效过程中组织和性能的变化。结果表明:时效1000~5000 h后,晶粒度未发生明显变化,但γ″相逐渐粗化,晶界δ相附近的γ″相贫化区逐渐加宽;时效4000 h时,晶内析出部分针状δ相;达5000 h时,在晶内析出魏氏体状δ相;经长期时效后合金室温和650℃拉伸性能变化不明显;合金持久寿命在时效2000 h内亦无明显变化,超过3000 h后,合金持久寿命则明显的降低,5000 h时合金持久寿命降低了近40%;添加的0.010%P元素,能显著降低Nb元素的扩散系数,从而降低强化相γ″相的长大速率,延缓γ″相向δ相转变,有效地抑制了长期时效后合金的拉伸和持久性能的衰减。     

均匀化处理对铸态GH625合金组织的影响

利用光学显微镜、扫描电镜和能谱分析等研究了采用真空感应熔炼和保护气氛电渣重熔工艺生产的GH625合金的铸态组织和均匀化热处理后的微观组织。结果表明:采用双联工艺生产的GH625合金电渣锭存在枝晶和元素偏析,其中Nb、Mo、Ti元素为主要偏析元素;均匀化热处理后枝晶消除明显,块状及条状碳化物碎化,棱角钝化;相同均匀化热处理工艺下Ti、Mo、Nb达到均匀化的难度依次加大;GH625合金最佳的均匀化热处理的工艺为1200℃保温24 h。     

钠冷快堆控制棒驱动机构用GH1059合金动导管的试制

采用真空感应+保护气氛电渣重熔冶炼出GH1059合金,经过锻造+热挤压+两个道次冷轧工艺成功研制出外径186 mm/内径104 mm的动导管.检测结果表明:GH1059合金动导管表面质量及尺寸精度优良,基体为全奥氏体组织,平均晶粒尺寸约为78.23 μm,晶内有近似圆形的含Cr、Fe、Ni、Mo的碳化物,晶内及晶界还有...     

镍基耐蚀合金925均匀化及固溶过程组织演变规律

为研究925合金在均匀化及固溶过程中组织演变规律,利用金相显微镜、扫描电镜和能谱分析等对经真空感应熔炼(VIM)和保护气氛下电渣重熔(ESR)双联工艺冶炼的925合金的原始铸态、均匀化态、锻态和固溶态的组织和析出相进行分析。结果表明：铸态组织中含有TiN、MC、γ′相、σ相以及η相;1160℃退火5h可使γ′相、σ相及η相回溶,退火20h偏析基本消除;在950-1070℃固溶过程中,M₂₃C₆相在晶界析出量逐渐减少,1040℃以上晶粒急剧长大。     

GH2747高温合金无缝管的试制

采用真空感应和电渣重熔工艺成功冶炼GH2747合金管坯,经过热穿孔、两道次冷轧及固溶热处理研发出规格为25 mm×3 mm的无缝管,并对其进行了无损检验、水压试验、表面检验、尺寸检测、化学成分分析、组织及性能检验。结果表明,GH2747高温合金无缝管工艺可靠,表面质量及尺寸精度良好;其化学成分满足GB/T 14992-2005的规定,各元素含量适中;无缝管基体为奥氏体等轴晶粒,平均晶粒度约为5.5级;无缝管的拉伸性能及维氏硬度、工艺性能及耐晶间腐蚀性能良好。研发出的GH2747高温合金无缝管的各项性能均满足其使用要求。     

GH2747高温合金无缝管的试制

采用真空感应和电渣重熔工艺成功冶炼GH2747合金管坯，经过热穿孔、两道次冷轧及固溶热处理研发出规格为25 mm×3 mm的无缝管，并对其进行了无损检验、水压试验、表面检验、尺寸检测、化学成分分析、组织及性能检验。结果表明，GH2747高温合金无缝管工艺可靠，表面质量及尺寸精度良好；其化学成分满足GB/T 14992-2005的规定，各元素含量适中；无缝管基体为奥氏体等轴晶粒，平均晶粒度约为5.5级；无缝管的拉伸性能及维氏硬度、工艺性能及耐晶间腐蚀性能良好。研发出的GH2747高温合金无缝管的各项性能均满足其使用要求。     

镍基耐蚀925合金均匀化及固溶过程组织演变规律

为研究925合金在均匀化及固溶过程中组织演变规律,利用金相显微镜、扫描电镜和能谱分析等对经真空感应熔炼(VIM)和保护气氛下电渣重熔(ESR)双联工艺冶炼的925合金的原始铸态、均匀化态、锻态和固溶态的组织和析出相进行分析。结果表明:铸态组织中含有TiN、MC、γ'相、σ相以及η相;1160℃退火5 h可使γ'相、σ相及η相回溶,退火20 h偏析基本消除;在950～1070℃固溶过程中,主要析出相M_(23)C_6在晶界析出量逐渐减少,高于1040℃时晶粒急剧长大。     

高纯HGCr15轴承钢的组织和性能的研究

采用真空感应和真空自耗双真空(VIM+VAR)冶炼工艺生产的HGCr15轴承钢,其中氧含量仅为(5～7)×10-6.电渣钢ZGCr15的氧化物夹杂含量是双真空HGCr15轴承钢的4.2倍.经真空热处理后轴承零件(HGCr15)表面可以获得压应力.双真空HGCr15的接触疲劳寿命L10是电渣钢的1.49倍,断裂韧度KIC提高19%.     

冶炼工艺对15—5PH钢质量影响

本文主要阐述了真空感应、电渣重熔、真空自耗重熔和AOD工艺冶炼的一些特点,以及采用不同工艺冶炼对15-5PH钢质量的影响,同时,对进口料也进行了解剖分析.采用现行三种工艺冶炼15-5PH钢,质量完全可以达到美国进口料的实物水平.通过对比分析认为,采用电炉 AOD 真空自耗工艺冶炼,在保持优良质量的前提下,可以大幅度降低成本,提高市场竞争力.     

Correlation of the Tensile Properties of Pure Magnesium and Four Commercial Alloys with Their Mode of Fracturing

Tensile tests were conducted on pure magnesium and on four commercial alloys over a variety of temperatures and strain rates. The high positive slope of the ductility vs testing temperature curves that is found over a short range of testing temperatures for these materials was shown to result from the fact that the microstructure was not stable at these testing temperatures. Pure magnesium did not display a transition temperature, although its sub-room temperature ductility was low. This poor ductility resulted from a grain boundary weakness. The aluminum-bearing commercial magnesium alloys had a higher ductility than the pure magnesium. These alloys did exhibit a transition temperature and grain boundaries that were stronger than the grain material. Both pure magnesium and the commercial alloys began initiating cracks at strains equal to one half of their fracture strain.     

Effects of cold working degrees on grain boundary characters and strain concentration at grain boundaries in Alloy 600

Strain concentration at grain boundaries and grain boundary microstructure in cold worked Alloy 600 were characterized. Excluding the annealing twin boundaries, the base and 20% cold worked alloys exhibited higher random grain boundary fractions than the 8% and 40% cold worked alloys. An increased low angle boundaries and decreased annealing twins were observed with deformation. The 20% cold worked alloy displayed a maximum strain concentration at grain boundaries. The stress corrosion cracking growth in cold worked Alloy 600 in high temperature water showed a strong correlation with the strain concentration at grain boundaries.     

热轧Mg-1Zn和Mg-1Y合金退火组织演变及静态再结晶行为

对比研究了高温轧制制备的Mg-1.02Zn及Mg-0.76Y(质量分数,%)合金在不同温度退火条件下的组织演变及静态再结晶和晶粒长大动力学行为.结果表明,Mg-1Zn合金的轧制组织以剪切带和孪晶为主,在剪切带和孪晶内伴随着动态再结晶;而Mg-1Y合金的轧制组织中只有孪晶,未观察到剪切带和再结晶发生.退火过程中,Mg-1Zn合金静态再结晶过程主要受控于形核过程,而Mg-1Y合金则既受控于形核过程又受控于长大过程.利用经典的JMAK模型和长大模型分别描述了2种合金热轧制后的静态再结晶和晶粒长大动力学过程,结果表明,静态再结晶过程的Avrami因子n值与理想预测值偏离可能来自于再结晶的不均匀形核.固溶稀土Y原子比Zn原子对晶界移动的拖曳作用更强,导致Mg-1Y合金比Mg-1Zn合金晶粒长大因子n’更高.     

动车组夹钳螺栓断裂原因分析

动车组制动夹钳紧固螺栓在安装过程中发生断裂。采用扫描电子显微镜、光学显微镜、电感耦合等离子体光谱仪等对断裂螺栓进行断口形貌、显微组织及化学成分检测与分析。结果表明：断裂螺栓化学成分、显微组织均未见明显异常;螺栓断面可见明显高温氧化痕迹和粗大晶粒轮廓,且局部晶界熔化,在圆角处与表面连通;原奥氏体晶粒内部和螺栓其他部位可见细小晶粒,结合螺栓制作工艺,可以推断该螺栓在热镦过程中因加热温度控制不当导致局部过烧。通过不同温度热镦试验,提出合理的工艺改进建议。     

元素Y对Mg—Cu系合金的组织结构和显微硬度的影响

采用铜板空冷和铜辊甩带的方法，研究元素Y对Mg-Cu合金的组织结构和室温硬度的影响。研究表明：元素Y形成的化合物最终富集于枝晶网胞间。随着元素Y的添加，Mg-Cu二元合金试样的晶粒显著细化，显微硬度大幅提高。另外，在快速冷却条件下，Mg90 Cu5Y5试样的微观结构为微晶和非晶的夹杂，形成非晶的能力大大增强。     

元素Y对Mg-Cu系合金的组织结构和显微硬度的影响

采用铜板空冷和铜辊甩带的方法,研究元素Y对Mg-Cu合金的组织结构和室温硬度的影响。研究表明:元素Y形成的化合物最终富集于枝晶网胞间。随着元素Y的添加,Mg-Cu二元合金试样的晶粒显著细化,显微硬度大幅提高。另外,在快速冷却条件下,Mg90Cu5Y5试样的微观结构为微晶和非晶的夹杂,形成非晶的能力大大增强。     

稀土Y对镁合金显微组织及腐蚀性能的影响

利用对掺法熔铸镁合金AJ61++xY,研究了合金中相的组成和分布及其在3.5%NaCl溶液中的腐蚀行为.结果表明,添加稀土Y使AJ61镁合金的晶粒明显细化,Mg17Al12相的数量明显减少且由连续网状变成弥散颗粒状分布,沿晶界处生成耐蚀稀土相Al2Y、Al3Y,AJ61镁合金的耐腐蚀性得到明显改善.耐腐蚀性顺序为:AJ...     

Effect of microstructure on tensile properties and fracture behavior of intermetallic Ti2AlNb alloys

The tensile properties and fracture behaviors of Ti-22Al-27Nb and Ti-22Al-20Nb-7Ta alloys were investigated in the temperature range of 25-800℃ Three typical microstructures were obtained by ifferent thermomechanical processing techniques.The results indicate that the duplex microstructure has an optimum combination of tensile yield strength and ductility both at room and elevated temperatures.Adding Ta to Ti2AlNb alloy can improve the yield strength,especially at high temperature while retain a good ductility.The study on crack initiation and propagation in dedformed microstructure of Ti2AlNb alloys indicates that microstructure has ikmportant effect on the tensile fracture mechanism of the alloys.The cracks initiate within primary O/α2 grains along O/B2 boundaries or O phase laths in B2 matrix,and propagate along primary B2 grain boundaries for the duplex microstructure.The fracture mode is transgranular with ductile dimples for the duplex and the equiaxed microstructures,but intergranular for the lath microstructure.     

Microstructure quantification of Cu-4.7Sn alloys prepared by two-phase zone continuous casting and a BP artificial neural network model for microstructure prediction

Microstructures of Cu-4.7Sn(%) alloys prepared by two-phase zone continuous casting(TZCC)technology contain large columnar grains and small grains.A compound grain structure,composed of a large columnar grain and at least one small grain within it,is observed and called as grain-covered grains(GCGs).Distribution of small grains,their numbers and sizes as well as numbers and sizes of columnar grains were characterized quantitatively by metallographic microscope.Back propagation(BP) artificial neural network was employed to build a model to predict microstructures produced by different processing parameters.Inputs of the model are five processing parameters,which are temperatures of melt,mold and cooling water,speed of TZCC,and cooling distance.Outputs of the model are nine microstructure quantities,which are numbers of small grains within columnar grains,at the boundaries of the columnar grains,or at the surface of the alloy,the maximum and the minimum numbers of small grains within a columnar grain,numbers of columnar grains with or without small grains,and sizes of small grains and columnar grains.The model yields precise prediction,which lays foundation for controlling microstructures of alloys prepared by TZCC.     

大晶粒FeAl合金超塑性变形的显微组织演变和变形激活能

本文对大晶粒ＦｅＡｌ金属间化合物塑性变形的微观组织演变进行了研究，并测定了其超塑性变形激活能，显微组织分析表明，合金的超塑性变形是一个晶粒变形，内部形成亚晶界，进而亚晶界向晶界转换，从而使晶粒得以细化的过程，Ｆｅ－３６．５Ａｌ，Ｆｅ－３６．５Ａｌ－１Ｔｉ和Ｆｅ－３６．５Ａｌ－２Ｔｉ合金变形激活能的测定值分别为３７０，２９０和２６０ｋＪ．ｍｏｌ＾－１大大低于其他的ＦｅＡｌ基合金蠕变激活能，表明超塑性