Microstructure evolution of Al-4Cu-Mg alloy during semi-solid treatment

The microstructure of a cold-deformed Al-4Cu-Mg alloy during semi-solid treatment was investigated, which shows that grain detachment and grain spheroidization processes during the semi-solid treatment are very important to control the fabricated semi-solid microstructures. For the two different processes, the driving force comes from the external heat source and the reduction in total interfacial area, respectively. The evolution models of microstructure morphology in the two processes were presented based on microstructure observations. It can be found that these models are useful to provide a reasonable estimated critical time of the evolution of microstructure during the semi-solid treatment.     

半固态Al-4Cu-Mg合金加工图研究

根据动态材料模型.建立了半固态Al-4Cu-Mg合金加工图.利用加工图确定了试验材料热变形的流变失稳区,结果表明半固态成形时的流变失稳区范围与应变速率有关.此外,获得了等温压缩试验参数范围内的热变形最佳工艺参数.半固态加工最佳工艺参数为加热温度560℃.应变速率0.001 s-1.     

Dynamic recrystallization during hot torsion of Al-4Mg alloy

Binary Al-4Mg alloy have been deformed by hot torsion at 300-500℃ and strain rates of 0,006-1.587 s-1 to a true strain of 5.5. The specimens were annealed in vacuum for 1.5 h at 500℃ and then water quenched. The study indicates that the dynamic recrystallization occurs during hot torsion of Al-4Mg alloy in a certain range of Z parameter (Zener-Hollmon Parameter), i.e. 19.3 ≤ lnZ ≤ 24.8. Increasing the strain rate at higher deformation temperature or reducing the strain rate at lower deformation temperature accelerates the occurrence of dynamic recrystallization in the alloy.     

半固态等温热处理对AZ91D镁合金组织的影响

研究了 AZ91 D镁合金在半固态等温热处理过程中 ,等温时间、等温温度对其组织形态和初生相尺寸的影响 .研究发现 :在升温过程中 ,晶界处的共晶组织 (δ+γ)中的 γ相先发生溶解 ,之后 ,随着温度进一步升高 ,δ相又发生熔化分离 ,并在等温处理过程中逐渐变为球状 .当等温时间过长时 ,球状颗粒有长大的趋势 ,结果表明 :在 570℃时保温 60 min,可得到初生相尺寸在 50～ 80 μm的球状组织 .     

Effects of Sb and heat treatment on the microstructure of Al-15.5wt%Mg2Si alloy

The modification effects of alloying element Sb and heat treatment on Al-15.5wt%Mg₂Si alloy were investigated by Olympus microscopy (OM), scanning electron microscopy and energy disperse spectroscopy (SEM-EDS), and X-ray diffraction (XRD). It is found that Sb plays a significant role in shaping primary Mg₂Si phase and eutectic Mg₂Si phase in Al-15.5wt%Mg₂Si alloy. The Sb addition of about 1.0wt% makes the resultant alloy show the finest primary Mg₂Si phase and the eutectic Mg₂Si phase with well distribution. But further increasing the Sb content decreases the amount of primary Mg₂Si phase, and some segregated phases appear at regions between the grains. In addition, heat treatment can modify the microstructural feature of Sb-modified Al-15.5wt%Mg₂Si alloy in terms of obviously shortening the nodulizing time of primary Mg₂Si phase and eutectic Mg₂Si phase.     

Direct preparation of semi-solid billets by the semi-solid isothermal heat treatment for commercial cold-rolled ZL104 aluminum alloy

Semi-solid isothermal heat treatment was proposed to directly process cold-rolled ZL104 aluminum alloys and obtain semi-solid billets. The effects of two process parameters, namely, temperature and processing time, on the microstructure and hardness of the resulting billets were also experimentally examined. Average grain size(AGS) increased and the shape factor(SF) of the grain improved as the process temperature increased. The SF of the grain also increased with increasing processing time, and the AGS was augmented when the processing time was prolonged from 5 to 20 min at 570°C. The hardness of the aluminum alloy decreased because of the increase in AGS with increasing temperature and processing time. The optimal temperature and time for the preparation of semi-solid ZL104 aluminum alloys were 570°C and 5 min, respectively. Under optimal process parameters, the AGS, SF, and hardness of the resulting alloy were 35.88 μm, 0.81, and 55.24 MPa,respectively. The Lifshitz–Slyozov–Wagner relationship was analyzed to determine the coarsening rate constant at 570°C, and a rate constant of 1357.2 μm~3/s was obtained.     

直接使用半固态等温热处理法将工业冷轧ZL104铝合金制备成半固态坯

Semi-solid isothermal heat treatment was proposed to directly process cold-rolled ZL104 aluminum alloys and obtain semi-solid billets. The effects of two process parameters, namely, temperature and processing time, on the microstructure and hardness of the resulting billets were also experimentally examined. Average grain size (AGS) increased and the shape factor (SF) of the grain improved as the process temperature increased. The SF of the grain also increased with increasing processing time, and the AGS was augmented when the processing time was prolonged from 5 to 20 min at 570°C. The hardness of the aluminum alloy decreased because of the increase in AGS with increasing temperature and processing time. The optimal temperature and time for the preparation of semi-solid ZL104 aluminum alloys were 570°C and 5 min, respectively. Under optimal process parameters, the AGS, SF, and hardness of the resulting alloy were 35.88 μm, 0.81, and 55.24 MPa, respectively. The Lifshitz–Slyozov–Wagner relationship was analyzed to determine the coarsening rate constant at 570°C, and a rate constant of 1357.2 μm3/s was obtained.     

Enhanced elevated temperature wear resistance of Al-17Si-5Cu alloy after a novel short duration heat treatment

The goal of the present study is to improve the elevated temperature wear resistance of an Al-17 wt%Si-5 wt%Cu alloy(AR alloy) by a novel short duration heat treatment process. The elevated temperature(100°C) dry sliding wear behavior of an AR alloy was studied after microstructural modification using the proposed heat treatment. The study revealed considerable microstructural modifications after the heat treatment and the heat treated alloy was designated as HT(heat treatment) alloy. A higher hardness value was obtained for the HT alloy compared to the AR alloy. Accordingly, the wear rate for the HT alloy was found to be significantly lower compared to the as-cast AR alloy at all applied loads. Accelerated particle pull-out for the AR alloy at elevated temperatures resulted in poor wear behavior for it compared to the HT alloy. On the other hand, the Si particles remained intact on the worn surface of the HT alloy due to the good particle/matrix bonding that resulted from the isothermal heat treatment. Furthermore, the age hardening that occurred in the HT alloy during wear provided additional wear resistance. Thus, the HT alloy at 100°C exhibited a lower wear rate compared to the AR alloy even at room temperature for all applied loads. This improvement was attributed to microstructural modification upon isothermal heat treatment along with the age hardening effect.     

电阻法探测Al和Al-Cu合金形核与初始生长

用电阻法探测了 Al和 Al-Cu合金的凝固过程 ,研究了形核与初始生长对电阻率的影响 ;观察到结晶开始时总是伴有电阻率突然升高现象 (呈山峰状 ) ;而添加晶粒细化剂后凝固开始时电阻率突然升高的峰值减小     

Mg-Gd-Y-Zr合金在773和823K热处理时的氧化行为

采用金相显微镜(OM)观察、X线衍射(XRD)、扫描电镜(SEM)和能谱分析(EDS)等分析测试技术,研究Mg-Gd-Y-Zr合金在773和823K热处理时的氧化行为。研究结果表明:合金热处理后表面氧化物的主要成分为Y2O3和Zr2Gd2O7的混合物;合金在773K保温48h热处理后,表面被轻微氧化,显微组织与热处理前无明显差别;合金在823K保温48h热处理后表面氧化严重,形成较厚氧化层,氧化层中沿晶界分布有很多尺寸为5~10μm的方形及形状不规则粒子;合金在773K热处理时不需用保护气氛,而在823K热处理需用保护气氛。     

多孔TC4钛合金吸氢规律

利用管式氢处理炉采取固态气相渗氢法进行置氢实验,以研究多孔TC4钛合金置氢过程中吸氢量随置氢温度、置氢时间和相对密度的变化规律,并建立了相应的数学模型.结果表明:当多孔钛合金的相对密度较低时,吸氢量随置氢温度的升高而增加;当相对密度较高时,吸氢量与置氢温度的关系遵循Sievert’s定律,与致密钛合金的吸氢特性一致;多孔钛合金随置氢时间的延长,吸氢量增加;随着多孔钛合金相对密度的增加,吸氢量降低.     

热处理工艺对Al-12.7Si-0.6Mg合金焊接接头组织性能的影响

采用ER5356焊丝对厚度为6 mm的T6态Al-12.7Si-0.6Mg合金进行平板对接试验,使用交流脉冲TIG单面双道焊缝成形工艺,获得了良好的焊缝成形并且对焊接后材料分别进行了T5和T6态热处理。研究表明:热处理前,焊接接头热影响区内存在软化现象,接头抗拉强度为157.58 MPa,经T5态和T6态热处理后,焊接接头强度分别增至265.34 MPa和308.09 MPa;焊后热处理使熔合区析出的Si颗粒重新固溶到基体中,形成Al-Si固溶体及细小的α-Al枝晶组织,与焊缝区的等轴晶过渡良好,热影响区的显著硬度提高,使断裂位置由热影响区转移至熔合区,接头的抗拉强度和屈服强度大幅度提高。     

Ti-6Al-4V钛合金长寿命疲劳试验

研究了Ti-6Al-4V在室温空气环境下的疲劳性能,获得疲劳寿命为107下的Goodman曲线.结果表明,用简化的Goodman直线代替Goodman曲线对于Ti-6Al-4V钛合金偏于保守.对断口形貌的观察表明应力比R在0附近时裂纹萌生于内部,而当应力比接近-1和1时裂纹萌生于表面.另外,研究了估算Ti-6Al-4V在不同应力比的疲劳强度估算公式,得出Ti-6Al-4V厚板和挤压件缺口试样估算公式的系数,分别为1.422和1.042.     

Transient spinodal decomposition during annealing of rapidly solidified Al-10Sr alloy

Rapidly solidified Al-10Sr alloy ribbons were prepared using a single roller melt spinning technique. The annealing process of the rapidly solidified Al-10Sr alloy has been carried out using differential scanning calorimetry (DSC). The microstructure of as-annealed Al-10Sr alloy has been characterized by transmission electron microscopy (TEM). The equilibrium AUSr phase is dominant in the as-annealed alloy. Besides the Al₄Sr phase, an AlSr phase is also found in the alloy isothermally annealed at 873 K for 90 min. Furthermore, a modulated nanostructure was observed in the alloy isothermally annealed at 873 K for 90 min. With further prolonged annealing time, however, the AlSr phase disappears in the as-annealed alloy. The dependence of particle size and growth rate on annealing time as well as the modulated structure shows that the occurrence of the AlSr phase may be due to the spinodal decomposition.     

镍基合金粉末的预变形与热处理

对镍基合金粉末进行了20%,40%,60%的预变形,并对不同变形量的粉末在1050℃,1100℃,1120℃温度下保温2h热处理.结果表明:在1050℃,形变量增至60%时,发生完全再结晶且组织均匀化程度显著增加;1 100℃时,显微组织基本上都已均匀,基体中沿再结晶晶粒的晶界均匀析出弥散分布的γ′相;1 120℃时,显微组织更为均匀,在晶界上析出粗大γ′相.     

置氢Ti-6Al-4V合金组织演变与超塑性能

应用高温拉伸实验研究了氢对Ti-6Al-4V合金超塑变形行为的影响,借助于OM、SEM、TEM和XRD等分析手段,分析了氢对钛合金组织演变的影响. 结果表明:氢可促进合金中β相数量的增加,氢质量分数达到0.2%时合金出现马氏体组织,并随着氢含量的增加而逐渐粗化;适量的氢可以改善钛合金超塑变形行为,如降低流动应力和超塑变形温度、提高应变速率敏感指数m值;Ti-6Al-4V合金加入质量分数0.1%的氢,其峰值流动应力降低53%,变形温度降低约60℃,且由于氢的加入,使得超塑变形后的位错密度减少,说明氢促进了位错的运动.     

Effect of equal channel angular pressing on aging treatment of Al-7075 alloy

The effect of aging treatment on microstructure and mechanical properties of equal channel angular pressed Al-7075 alloy was examined.Commercial Al-7075 alloy in the solid solution heat-treated condition was processed by equal channel angular pressing through route BCat both the room temperature and 120 1C. Only three passes of equal channel angular pressing was possible due to the low ductility of the alloy at both temperatures. Followed by equal channel angular pressing, the specimens have been aged at 120 1C for different aging times. Mechanical properties were measured by Vickers microhardness and tensile tests and microstructural observations were undertaken using transmission electron microscopy, X-ray diffractometer as well as optical microscopy. Microstructural investigations showed that ultrafine-grained materials with grain size in the range of 200–350 nm and 300–500 nm could be obtained after three passes of equal channel angular pressing at room temperature and 120 1C, respectively. Equal channel angular pressing of solid solution heat-treated Al-7075 alloy accelerates precipitation rate and subsequently leads to a significant decrease in aging time to attain maximum mechanical properties. Furthermore, it is possible to achieve maximum mechanical properties during equal channel angular pressing at 120 1C as a result of dynamic aging and formation of small η′ phase.     

Morphology and quantitative analysis of O phase during heat treatment of hot-deformed Ti_2AlNb-based alloy

A 1040°C-hot-deformed Ti_2AlNb-based alloy solution-treated at 950°C and aged at different temperatures was quantitatively investigated. The microstructure, size of the phase, and microhardness of the deformed alloys were measured. The results indicated that the microstructure of the deformed Ti_2AlNb-based alloy specimens comprise coarse O lath, fine O lath, equiaxed O/α_2, and acicular O phase. More O phase was generated in the deformed alloy after heat treatment because the acicular O phase was more likely to nucleate and grow along the deformation-induced crystal defects such as dislocations and subgrain boundaries. After deformation and subsequent heat treatment, the acicular O phase of the resultant alloy became finer compared to that of the undeformed alloy, and the acicular O phase became coarser and longer with the elevated aging temperature, while the width of the O lath exhibited unobvious variations. The hot deformation facilitated the dissolution of the O lath but accelerated the precipitation of the acicular O phase. When the 950°C-solution-treated deformed Ti_2AlNb-based alloy was then aged at 750°C for different periods, the phase content was nearly invariable, O and B2 phases eventually reached equilibrium, and the microstructure became stable and homogeneous.     

Effects of conform continuous extrusion and heat treatment on the microstructure and mechanical properties of Al-13Si-7.5Cu-1Mg alloy

The effects of conform continuous extrusion and subsequent heat treatment on the mechanical and wear-resistance properties of high-alloying Al-13Si-7.5Cu-1Mg alloy were investigated. The microstructures of alloys before and after conform processing and aging were compared by transmission electron microscopy and scanning electron microscopy, respectively. The results reveal that the primary phases were broken and refined by intense shear deformation during conform processing. After the conform-prepared Al-13Si-7.5Cu-1Mg alloy was subjected to solid-solution treatment at 494℃ for 1.5 h and aging at 180℃ for 4 h, its hardness improved from HBS 115.8 to HBS 152.5 and its ultimate tensile strength increased from 112.6 to 486.8 MPa. Its wear resistance was also enhanced. The factors leading to the enhanced strength, hardness, and wear resistance of the alloy were discussed in detail.     

钽涂层对Ti-6Al-4V合金抗腐蚀性能的影响

摘要：目的 在模拟体液环境中,研究钽（Ta）涂层对Ti-6Al-4V合金抗腐蚀性能的影响。方法 对Ti-6Al-4V合金试样采用等离子喷涂技术在其表面形成一层500μm厚的钽涂层。通过模拟体液环境下电化学测量法对比涂层前后的试样抗腐蚀性能的强弱。结果 塔菲尔极化曲线图形显示,Ti-6Al-4V合金经钽涂层处理后表现出阳极和阴极极化曲线低平,自腐蚀电位向正方向移动,钝化区间变长,而维钝电流降低。结论 Ti-6Al-4V合金表面涂覆钽涂层的表面改性处理能有效提高基体金属的抗腐蚀性能,为解决人工关节无菌性松动及Ti-6Al-4V合金关节假体的优化提供了发展方向。