Predicting phase equilibrium,phase transformation,and microstructure evolution in titanium alloys

Phase transformation and microstructural evolution in commercial titanium alloys are extremely complex. Traditional models that characterize microstructural features by average values without capturing the anisotropy and spatially varying aspects may not be sufficient to quantitatively define the microstructure and hence to allow for establishing a robust microstructure-property relationship. This article discusses recent efforts in integrating thermodynamic modeling and phase-field simulation to develop computational tools for quantitative prediction of phase equilibrium and spatiotemporal evolution of microstructures during thermal processing that account explicitly for precipitate morphology, spatial arrangement, and anisotropy. The rendering of the predictive capabilities of the phase-field models as fast-acting design tools through the development of constitutive equations is also demonstrated. For more information, contact Y.-Z. Wang, Department of Materials Science & Engineering, Ohio State University, 2041 College Road, Columbus, OH 43221, USA; (614) 292-0682; fax (614) 292-1537; e-mail wang.363@osu.edu.     

Mechanical relaxations in polybutene-1 and poly-4-methylpentene-1

Dynamic mechanical measurements between — 180°C and 180°C were made on both isotropic and drawn samples of polybutene-1 (PB-1) and poly-4-methylpentene-1 (P4MB1) over a wide frequency range by the use of a torsional pendulum (0.3–3 Hz), a viscoelastic spectrometer (5–90 Hz) and ultrasonic technique (3 MHz). The relaxation peaks were identified and the associated activation energies determined from Arrhenius plots. For PB-1 it was observed that orientation reduces the height and shifts up the temperature of the α_a-peak associated with large scale main-chain motion in the amorphous regions, but has little effect on the β-peak associated with side-group motion. In addition to the α_a and β relaxations a high-temperature crystalline relaxation (α_c) is also observed in P4MP1. For both the α_c and β relaxations the mechanical loss at 45° to the draw direction is much larger than that at 90°, which indicates that shear processes are involved in these relaxations.     

纺牵—步法中粗旦丙纶长丝沸水收缩率初探

在纺牵联合一步法纺丝机上研究了丙纶切片的熔融指数对纤维沸水收缩率的影响，发现熔融指数高的切片，其纤维的沸水收缩率变化大。沸水收缩率随热定型的温度升高而下降。沸水收缩率可根据用户提供中心值（Ｍ）通过实验确定，一般以Ｍ±１．５为宜。     

Toughening by Metallic Lamina in Nickel/Alumina Composites

Tape casting and hot-pressing were used to produce metal/ alumina laminate composites. The mechanical behavior of these laminates was characterized. The strength and toughness of the laminates were greatly improved in comparison to that of monolithic alumina. Indentation strength values of the laminates remained approximately constant for indent loads between 10 and 100 N. Thus, this type of laminate appears to be a good candidate for damage-tolerant composite material design.     

α,β,γ,δ-四-(4-吡啶)卟啉分光光度法测定瓷餐具铜溶出量

本文提出用α，β，γ，δ-四-（4-吡啶）卟啉为显色剂，分光光度法测定瓷餐具铜的溶出量，该方法灵敏度高，选择性好，可以不经分离，直接对试样进行测定，操作简便，结果满意。     

SO_4~（2－）／ZrO_2固体超强酸的失活与再生

初步探索了ＳＯ_４~２－／ＺｒＯ２固体超强酸的失活机理．并着重研究了催化剂的两种再生方法：灼烧法和溶剂洗涤法。催化剂主要是因结焦而失活，高温灼烧能基本恢复催化剂原有活性．且再生效果与灼烧温度有关。溶剂洗涤法有一定的再生能力，但不显著．     

Contents Volume 10 (2003)

Volume Contents

Contents Volume 10 (2003)     

Effects of hydrogen on the transition layers between diamond films and Zr, Hf substrates

Highly purified polycrystalline wafers of Zr and Hf were chosen as substrates for diamond deposition by means of the d.c. arc discharge plasma CVD method. Polycrystalline diamond films were formed on both substrates. Scanning electron microscopy and high resolution X-ray diffraction were used to investigate the surface morphology of the diamond films and the composition of the interface layers between the diamond films and substrates. The experiments showed that the transition layer between the diamond films and Zr substrates was ZrC, ZrH and ZrC_0.32H_1.2. For Hf substrates, in addition to HfC, it is supposed that there were also some hydrides or carbohydrides in the transition layer, because several X-ray reflections appeared which could not be assigned to Hf, HfC or diamond.