微合金元素对V-N中碳微合金钢组织和性能的影响

采用金相显微镜和透射电镜等分析方法研究了微合金元素对V-N中碳微合金钢组织和性能的影响.结果表明,V-N中碳微合金钢的热轧态组织为铁素体+珠光体组织,随着钢中V、N含量增加,铁素体含量增多,晶粒变细;微合金钢中的V、Ti、N等元素主要以V(C,N)和V(C,N)+Ti(C,N)形式析出,其中V(C,N)颗粒细小,而V(C,N)+Ti(C,N)颗粒较粗大;细小、弥散分布在钢中的V(C,N)相以析出强化的方式改善了中碳微合金钢的综合力学性能;而适量的Ti在钢中形成弥散分布的TiN相阻止热加工过程中奥氏体晶粒的过分长大,细化了微合金钢的组织.     

热连轧过程复合微合金碳氮化物析出的定量计算

以微合金元素的析出热力学和析出动力学为基础,针对Fe-Nb-V-Ti-Al-C-N合金系,定量计算了热连轧过程中(Nb,V,Ti)(C,N)和AlN在奥氏体中的析出行为,并进一步分析了热轧制温度对析出行为的影响。计算结果表明,对所研究的钢种成分和工艺条件,在加热过程中(Nb,V,Ti)(C,N)就已经析出,在粗轧阶段,(Nb,V,Ti)(C,N)析出粒子平均半径逐渐减小,在精轧阶段,(Nb,V,Ti)(C,N)基本达到平衡析出量,终轧后析出粒子平均半径保持在23 nm左右。轧制时的热变形增大了形核率,促进了析出,使析出粒子的平均半径减小。随加热和轧制温度的降低,(Nb,V,Ti)(C,N)的析出量有所增加,粒子平均半径减小。     

微合金元素Nb,Mo在应变诱导析出过程中的相互作用

运用热模拟技术和透射电子显微镜,研究了C-Mo、C-Ti-Mo和C-Nb-Mo三种简单成分钢奥氏体变形后松弛过程中微合金元素Nb、Mo在析出物中的相瓦作用.结果表明:在850℃变形后松弛1000 s.三种钢均保持了奥氏体状态,但C-Ti-Mo和C-Nb-Mo钢有析出发生,能谱分析显示析出颗粒分别是Ti(C,N)和含Mo的Nb(C,N).微合金元素Mo与Nb有较强的相互作用,在Nb(C,N)析出后,Mo可能溶入Nb(C,N)的析出颗粒之中.     

低碳钢中微合金元素Nb，Mo在析出过程中的相互作用

运用热模拟技术和TEM分析法，研究了C-Ti．Mo和C-Nb-Mo两种简单成分钢奥氏体变形后弛豫过程中微合金元素Nb，Mo在析出物中的相互作用。结果表明：在850℃变形后弛豫1000s，C-Ti-Mo和C-Nb-Mo钢均保持了奥氏体状态且两种简单成分钢中均有析出发生，能谱分析显示析出颗粒分别是Ti（C，N）和含Mo的Nb（C,N）。微合金元素Mo与Nb有较强的相互作用，在Nb（C,D）析出后，Mo可能溶入Nb（C，N）的析出颗粒之中。     

低碳钢中微合金元素Nb,Mo在析出过程中的相互作用

运用热模拟技术和TEM分析法,研究了C-Ti-Mo和C-Nb-Mo两种简单成分钢奥氏体变形后弛豫过程中微合金元素Nb,Mo在析出物中的相互作用.结果表明:在850℃变形后弛豫1000s,C-Ti-Mo和C-Nb-Mo钢均保持了奥氏体状态且两种简单成分钢中均有析出发生,能谱分析显示析出颗粒分别是Ti(C,N)和含Mo的Nb(C,N).微合金元素Mo与Nb有较强的相互作用,在Nb(C,N)析出后,Mo可能溶入Nb(C,N)的析出颗粒之中.     

Nb-V-Ti和V-Ti微合金钢中碳氮化物的回溶行为

采用TEM和EDX技术,研究了低碳微合金钢中Nb,V,Ti的碳氮化物在不同温度保温后的回溶行为.结果表明,Nb-V-Ti微合金钢中存在尺寸明显不同的两类析出,较大的析出颗粒平均尺寸在80 nm以上,其心部为(Nb,V,Ti)(C,N),而边部为(Nb,Ti)(C,N),较小的析出颗粒平均尺寸在20 nm以下,其类型为(Nb,Ti)(C,N).两类析出物中Nb/Ti原子比均随回溶温度的升高而减小.V-Ti微合金钢中,Ti的存在对V的回溶具有拖曳作用,提高了V的碳氮化物的热稳定性.Nb-V-Ti微合金钢中,由于Nb,V,Ti之间综合作用,使得析出相中V具有更高的热稳定性.     

Nb-Ti微合金钢中第二相的溶解行为

利用碳萃取复型、TEM和EDX分析,研究了低碳Nb-Ti微合金钢在1 300℃等温过程中第二相粒子的溶解行为。实验结果表明:钢中有两类尺度存在显著差异的析出颗粒,其一为尺寸在50 nm以上的富钛相(生成于钢液凝固阶段),其二为尺寸小于20 nm的富铌相(形成于奥氏体变形过程)。在1 300℃保温2 h后,应变诱导析出相基本消失,而凝固过程中形成的析出相在保温48 h后,还存在含Nb的(Nb,Ti)(C,N)复合相。在微合金钢中含Ti的情况下,碳氮化物的稳定性大幅提高。这些结果表明,析出相的形成和热稳定性在很大程度上取决于Nb和Ti原子的相互作用。     

超低碳微合金钢中碳氮化物的溶解行为

利用萃取复型,结合TEM和EDX技术,研究了超低碳Nb-Ti微合金钢中析出相粒子在1300℃保温后的回溶行为.结果表明,基体中存在两类析出相:一类为凝固过程中形成的比较粗大的析出相,另一类为应变诱导下产生的析出相,尺寸比较细小.凝固过程中形成的析出相中富Ti,应变诱导下的细小析出相富Nb.在1300℃回溶时应变诱导析出相不稳定,2h后基本不存在,而凝固过程中形成的析出相在回溶48 h后,还存在含Nb的(Nb,Ti)(C,N)复合相.在钢中含Ti的情况下,Nb碳氮化物的稳定性大幅提高.     

低碳微合金钢中Nb、V、Ti碳氮化物的回溶研究

采用透射电镜和X射线光谱技术,研究了低碳微合金钢中Nb、V、Ti的碳氮化物在不同温度保温1 h后的回溶行为.结果表明,低碳微合金钢中存在尺寸明显不同的两类析出,其中颗粒尺寸较大的在80 nm以上;这种颗粒的心部是(Nb,V,Ti)(C,N)相,而颗粒边缘为(Nb,Ti)(C,N)相;颗粒尺寸较小的在20 nm以下,其类型为(Nb,Ti)(C,N).两类析出物中Nb与Ti的原子比均随回溶温度的升高而减小.     

裂解加工汽车连杆用V-N微合金锻钢的连续冷却转变

通过热模拟试验方法对V-N微合金锻钢的奥氏体连续冷却转变进行研究,结果表明,在较低的冷却速度下,V-N微合金锻钢发生γ→α+р转变,且珠光体比例和晶粒度随着冷却速度提高而增多、增大,但在高的冷却速度下,V-N微合金锻钢直接发生γ→M转变,最终产物为马氏体组织;同时,V-N微合金锻钢在连续冷却转变过程中会析出V（C, N）等析出相,在较低的冷却速度下,这些析出相数量多而细小,但当冷却速度增大到一定程度后（≥10 ℃/s）,共析相变被抑制,第二相的析出被抑制。     

The influence of hot deformation on the microstructure of Ni-Al and Ni-Al-Fe alloys with small Ti2B addition

Results of microstructure investigation of Ni-Al and Ni-Al-Fe alloys with addition of 0.5at.% Ti₂B after hot deformation are presented. Ti partially dissolves in the matrix, promoting formation of a discontinuous phase and precipitates of γ′ phase of Ll₂ structure during hot deformation of Ni-Al and Ni-Al-4.3at.%Fe alloys. In all investigated alloys precipitates of different compositions, enriched in Ti, were noticed. A compression test proved that due to the grain boundaries strengthening, the fracture mechanism changes into a transcrystalline one, improving fracture toughness of the hot deformed alloy. Fracture occurs in the deformation induced Ll₀ martensite.     

钒氮非调质钢的组织细化

为研究静态再结晶过程中析出相对组织的细化作用,选取先前研究的V-N非调质钢作为试样,在Gleeble-1500D热模拟机上进行单道次与双道次压缩实验,计算了不同等温时间下的再结晶分数,采用带有STEM附件、INCA能谱仪及GIF能量过滤器的透射电镜JEM-2100F分析了析出相。结果表明:道次等温期间奥氏体中析出相主要为尺寸在55～140 nm的(Ti,V)(C,N);相变冷却期间铁素体中析出相则为细小的长22～100 nm、宽13～39 nm的VC。静态再结晶与析出相相互竞争、共同细化组织。等温时间较短,静态再结晶起主要细化作用;析出相数量随等温时间延长而增加,使静态再结晶出现停滞平台;等温时间较长,奥氏体局部出现的溶质贫乏区促进了晶内铁素体形核,使组织细化。     

TSCR工艺生产Ti-IF钢中第二相粒子析出行为的模拟研究

研究了模拟薄板坯连铸连轧工艺（Thin Slab Casting and Rolling）生产Ti-IF钢的析出行为.利用透射电镜分析了铸坯连续快速冷却及热连轧过程Ti-IF钢中第二相粒子的析出行为特征,将TiS,Ti4C2S2等析出粒子的尺寸、分布及数量分别与传统工艺的析出物进行了分析比较.结果表明,TSCR生产的Ti-IF钢析出物比传统工艺更为粗大,且发现有较粗大的TiC和Ti4C2S2的复合析出物.     

轧制变形对网状结构TiB_w/Ti复合材料组织与力学性能的影响(英文)

通过反应热压技术成功制备出网状结构TiB晶须增强纯钛(TiBw/Ti)复合材料。原位合成的TiB晶须分布在大尺寸Ti基体颗粒周围形成网状结构。这种新型的网状结构TiBw/Ti复合材料表现出优异的综合力学性能。为了进一步改善力学性能及指导后续塑形变形加工,研究这种新型复合材料的轧制变形行为。结果表明:由于基体的形变强化,这种新型TiBw/Ti复合材料的强度可以通过轧制变形得到有效的提高,并且强度水平随着变形量的增加而增加。其中,通过轧制变形,可以使8.5%TiBw/Ti复合材料的强度从842MPa提高到 1030 MPa。需要指出的是,随着变形量的增加,TiB晶须的断裂程度也增加,这一点对复合材料的力学性能是不利的。     

Ti–Cu–Ni shape memory bulk metallic glass composites

New Ti–Cu–Ni shape memory bulk metallic glass composites were obtained by carefully controlling the cooling rate upon quenching. This allows for the formation of a metastable microstructure consisting mainly of ductile, spherical martensitic Ti(Ni,Cu) precipitates embedded in an amorphous matrix also containing a small volume fraction of TiCu and Ti₂Cu precipitates. These composites exhibit large ductility and high strength combined with a strong work-hardening behaviour. A deformation mechanism is proposed with the help of experimental observations and finite-element simulation. The simulation results demonstrate that stress concentrations occur around the precipitates, which promotes a heterogeneous stress distribution and the formation of multiple shear bands. Additionally, different transformation temperatures were observed for martensitic precipitates depending on whether they are completely or partially embedded in the amorphous matrix.     

Processing,Microstructure and Mechanical Properties of Ti6Al4V Particles-Reinforced Mg Matrix Composites

Novel Ti6Al4V particles-reinforced AZ91 Mg matrix composites were successfully fabricated by stir casting method. The stirring time in semisolid condition directly affected the particle distribution and the quality of the ingots.Furthermore, the optimal speed of the heating and the liquid stirring could overcome particle settlement caused by the density difference between the matrix and the particles. Ti6Al4V particles distributed uniformly in the composites with different particle contents. The average grain size decreased with the increase in the particle contents. The Ti6Al4V particles bonded pretty well with the alloy matrix. In addition, there were some interfacial reactions in the composites.There were rod-like Al_3Ti phases at the interface. The precipitates extended from the particle surface to the matrix, and they might improve the interfacial bonding strength. The ultimate tensile strength, yield strength and elastic modulus were enhanced as the particle contents increased, and the elongation was much better than that of the same matrix material reinforced with SiC particles. Thus, the novel composites exhibit better comprehensive mechanical properties.     

Effects of rolling deformation on microstructure and mechanical properties of network structured TiBw/Ti composites

TiB whiskers reinforced pure Ti (TiB_w/Ti) composites with a novel network microstructure were successfully fabricated by reaction hot pressing (RHP). TiB whiskers are in situ synthesized around the large pure Ti matrix particles, and subsequently formed into TiB_w network structure. The novel TiB_w/Ti composites with a network microstructure exhibit a superior combination of mechanical properties. In order to further improve the mechanical properties and guide the subsequent plastic forming, the rolling deformation behavior of the novel composites was investigated. The results show that the strength of the novel TiB_w/Ti composites can be effectively enhanced by rolling deformation due to the matrix deformation strengthening effect, and increased with increasing the rolling reduction. The strength of 8.5%TiB_w/Ti (volume fraction) composite is significantly increased from 842 MPa to 1030 MPa by rolling deformation. It is certain that the TiB whiskers are gradually broken with increasing the rolling reduction, which is harmful to the mechanical properties of the composites.     

反应热压(Al2O3+TiB2+Al3Ti)/Al复合材料的组织形成机制

采用B或B2O3、TiO2和Al粉反应热压制备了原位 (Al2O3 TiB2 Al3Ti)/Al复合材料,采用光学显微镜、扫描电镜和透射电镜分析了原位复合材料的显微组织.热压状态下,反应生成相Al3Ti呈大块不规则形状,尺寸约几十微米; Al2O3和TiB2为细小弥散质点,TEM分析发现TiB2颗粒呈六边形,而Al2O3颗粒呈等轴状.在以Al粉、TiO2粉和B粉为原料制备的复合材料中,除反应生成了大块的Al3Ti相外,还有细小针状Al3Ti相沉淀析出,且呈弥散分布.热挤压后大块的Al3Ti被破碎成细小弥散质点.Al2O3在TiO2和B2O3粉末表面生成; TiB2在B或B2O3粉表面形成,因而均呈弥散分布,且尺寸细小.自TiO2中还原出的Ti溶入液态Al中形成Al3Ti时,Ti可在液态Al中长距离扩散,因而Al3Ti呈大块不规则状.     

粉末冶金Al3(Zr,Ti)/Al复合材料的组织与性能

为了研究Zr含量变化对Al-Ti-Zr铝基复合材料组织与力学性能的影响,以纯Al粉末作为基体材料,纯Ti粉和纯Zr粉作为增强体材料,采用粉末冶金原位合成法在750℃烧结制备了Al-Ti-Zr复合材料。随后将烧结制备的复合材料加热到400℃进行热压变形处理,测试其组织和性能的变化。结果表明:在Al-Ti-Zr三元体系中,复合材料内部通过置换反应生成Al3(Zr,Ti)化合物;随着Zr含量的增加,复合材料的组织更加均匀、致密化,其抗拉强度、硬度逐渐增加,抗拉强度最大值为227.66 MPa,硬度最大值为132.83 HV0.025;复合材料的耐腐蚀性能随着Zr含量的增加呈现下降趋势,在Zr含量为5%时,复合材料的耐腐蚀性能最佳,其腐蚀电位为-0.67661 V,腐蚀电流密度为1.0214×10^-6 A/cm^2。