CHEN Shan-hua, G. SCHUMACHER. Quantitative Analyses of γ/γ Interfacial Relations of TiAl-based Alloy[J]. Journal of Materials Engineering, 2004, 0(5): 3-6,11.
The γ/γ lamellar interfaces play a critical role in the mechanical properties of (γ+α2) two phase TiAl-based alloys. An umambiguous experimental determination of all six domain orientaions in lamellar structure and the interface types between neighboring γ laths in a (γ+α2) two-phase TiAl alloy containing Mn and Nb were analysed by means of convergent-beam electron diffraction. The results show that a single High-Order-Laue-Zone (HOLZ) line pattern is adequate to uniquely describe the γ lath orientation, and four types of interfaces, i.e., 120° rotational interfaces, true-twin interfaces, pseudo-twin interfaces and antiphase boundaries occurred in the present alloy. The statistical analysis shows that among the possible interface types, true-twin related interfaces are observed most frequently, while the pseudo-twin interfaces and the 120° rotational interfaces are less. The occurrence of antiphase boundaries in this alloy is rather low.
WANG Kai-guo, LI Jia-rong, LIU Shi-zhong, LI Ying, CAO Chun-xiao. Study on Creep Properties of Single Crystal Superalloy DD6 at 760℃[J]. Journal of Materials Engineering, 2004, 0(5): 7-11.
The creep properties of the second generation single crystal superalloy DD6 with [001], [011] and [111] orientations have been investigated under different stress levels at 760℃. The results show that the creep properties of DD6 are obviously anisotropic. Creep time decreases in the order [111], [001], [011] under the same test conditions. Stationary strain rates of [001], [011] and [111] orientations are different under the same test conditions. The types of matrix channel with different orientations differ each other and the stress level varies with different matrix channels. The creep deformation at small strains mianly concentrates on the highly stressed matrix channels.
YUAN Chao, GUO Jian-ting, JI Guang. High Temperature Mechanical Behavior of a Cast Nickel-base Superalloy with Low Cost[J]. Journal of Materials Engineering, 2004, 0(5): 12-15,39.
The tensile, creep and stress-rupture properties at high temperature of a cast nickel-base superalloy K46 without cobalt, as comparison with superalloy K412, were investigated. The results show that the tensile and stress-rupture strength at high temperature of alloy K46 are higher than that of alloy K412, but the cost of the former is lower than the latter. At 950℃, the alloy K46, usually being worked under 800℃, has enough strength and ductility to safety use. It is found that the creep curves of alloy K46 consist mainly of a longer steady-state creep stage and an accelerated creep stage, which occupies the most creep strain. It is thought that the creep deformation mechanism of alloy K46 is controlled by the dislocation climb around the γ′particles. It is observed that the tensile, creep and stress-rupture fracture process have the intergranular characteristics.
LI Jin-ping, MENG Song-he. Effect of Added Fe Element on Microstructure of CuCr Contact Materials[J]. Journal of Materials Engineering, 2004, 0(5): 16-18,22.
CuCr and CuCrFe contact materials were made by mechanically alloying, explosive compaction and sintering at low temperature. OM, SEM and TEM were used to observe their microstructure, it was studied mainly the effect of the added Fe element on microstructure of CuCr contact materials. The results show that the effect of the added Fe is more obvious and microstructure of the CuCrFe alloys is much finer than that of CuCr alloys; a majority of Fe dissolves into Cr phase, and the added Fe does not make strain strips and dislocation vanish, on the contary, it makes riffled dislocation appear so that conductivity of CuCr alloys is much lower.
HE Xiao, WU Yan, CAO Jian-ling, SHEN Bao-luo. Investigation on Static and Dynamic Fracture Behavior of Hydrogen-bearing Ti-2Al-2.5Zr Alloy[J]. Journal of Materials Engineering, 2004, 0(5): 19-22.
The compact tension(CT) samples of Ti-2Al-2.5Zr titanium alloy bearing 110μg/g hydrogen were employed to study behaviors of sustain load cracking(SLC) and fatigue cracking. Fracture surfaces were observed by SEM. Results show that this alloy containing 110μg/g hydrogen is easily subject to delayed hydrogen cracking(DHC), which owes to hydrogen diffusing to the crack tip accumulating, leading to hydrides precipitating and separating from substrate. But for fatigue loading, the same content hydrogen has little effects on cracking, which is controlled by the normal fatigue fracture mechanism of crack initiation, stable propagation and sudden rupture process.
HUANG Yuan-lin, MA Shi-ning, LI Chang-qing, LI Xin. Comparison of Properties Between Anodic Oxide Film and Ti(C,N)/TiN Multi-element-layer Film Prepared on Aluminium Alloy[J]. Journal of Materials Engineering, 2004, 0(5): 23-25,29.
Ti(C,N)/TiN/Ti(C,N)/TiN/Ti(C,N)/TiN six-layer multi-element-layer film and anodic oxide film were prepared on LF6 substrate by multi-arc ion plating and anodic oxide respectively. Their Mechanical and tribological properties were investigated. The results show that their critical loads are 76N and 60N respectively, microhardnesses are HV0.251404 and HV0.25520 respectively, and their friction coefficients are 0.66 and 0.76 respectively which are relatively high and result in wear of counter object. But both hardness and wear resistance of multi-element-layer film increase by 3 times compared with that of anodic oxide film. Furthermore, friction coefficient curve of multi-element-layer film presents smooth, which shows that the film is worn steadily, but that of anodic oxide film presents jumping, which shows worn of the film is not steadily.
YIN Zhan-hua, LI Wo-guang, YU Ye-qiu. Mechanical and Memory Performance of CuAlNi Shape Memory Alloy Wires Cast by Ohno Continuous Casting Process[J]. Journal of Materials Engineering, 2004, 0(5): 26-29.
CuAlNi alloy wires in 1.5mm diameter were cast by ohno continuous casting process to obtain a longitudinal columnar structure. After solution treatment at 900℃, the stress curve of the wires shows two martensitic transformation stages which is similar to that of single crystal structure. The wires show a ultimate tensile strength of 633MPa, elongation of 14.95%. Under 4% strain, the number of repeat tensile fatigue rupture is 38560 cycles and the recovery rate keeps up 100%. After repeat tensile, a new phase forms along the boundaries so as to release stress concentration. This is probably the cause of great enhancement of repeat tensile fatigue life.
HUAI Li-min, CUI Li-shan, ZHANG Lai-bin, ZHENG Yan-jun. Reverse Martensitic Transformation Temperatures of TiNi Wires Prestrained under Different Methods[J]. Journal of Materials Engineering, 2004, 0(5): 30-32.
The reverse martensitic transformation behavior of TiNi shape memory alloy wires prestrained by cooling under constant strain constraint and prestrained by tension at room temperature were investigated. The results show that the reverse martensitic transformation temperatures of both wires increase and the recovery strain ratio of the both decrease with increasing prestrain, however, the reverse martensitic transformation temperature of the former is lower than that of the latter and the recovery strain ratio of the latter is higher than that of the former.
HUANG Li-jun, WANG Bao, GAO Yang. Investigation of TC4 and TC11 Titanium Alloys′ Combustion Resistance Properties[J]. Journal of Materials Engineering, 2004, 0(5): 33-35.
The combustion resistance properties of TC4 and TC11 titanium alloys had been studied by means of titanium combustion testing equipment and metallographic examination. The microstructure character of the combustion products had been analyzed. A formula, with regard to the impact pressure and the yield strength of the materials, had been deduced according to the tribology theory. Consequently, the reason, why different alloys need different critical impact pressure to lead into steady combustion state with identical circumstance, had been explained by this formula. Several approaches of developing combustion resistance titanium alloys had been suggested according to the conclusion.
ZHANG Jian, XU Zhi-feng, ZHENG Hai-zhong, HUANG Yin-Hui. Preparation of Polymer /Al2O3 Nano-composites by Selective Laser Sintering[J]. Journal of Materials Engineering, 2004, 0(5): 36-39.
A new practical method for preparation of bulk polymer/Al2O3 nano-composites by selective laser sintering(SLS) was introduced. The results show that under the proper processing parameter conditions, surface pretreatment polymer and nano-Al2O3 mixture powders can be produced into bulk polymer/Al2O3 nano-composites, which nano-sized Al2O3 particles are uniformly located within polymer matrix, and different properties of polymer/nano-composite can be obtained by controlling laser power, scanning speed and other factors.
TONG Jian-feng, CHEN Da-ming, LIU Xiao-guang, LI Bao-wei. Preparation of Nanoscale MgAl2O4 Powders by Aqueous Polymer Network Gel Method[J]. Journal of Materials Engineering, 2004, 0(5): 40-41,48.
Nanoscale MgAl2O4 ceramic powders were prepared by the aqueous polymer gel method. The preparing process was studied. The results show that polymer network inhibits the aggregate of MgAl2O4,nanoscale MgAl2O4 powders with 50nm size are obtained. Its calcinations temperature is 900℃,which is 100℃ lower than the general calcinations temperature.
GU Dong-dong, SHEN Yi-fu, PAN Yan-feng, XU Cheng-ting. Research on Mechanism of Direct Metal Laser Sintering[J]. Journal of Materials Engineering, 2004, 0(5): 42-48.
Sintering mechanism of the single-component/multi-component metal powders and the pre-alloyed powders during Direct Metal Laser Sintering (DMLS) process were analyzed. The material properties such as surface tension, viscosity, particle size and its distribution, and absorbance/ reflectivity together with the processing variables such as laser parameters, layering thickness of powders, atmospheric control, bed pre-heating temperature, and sintering assisted material, which affect sintering and densification of DMLS-processed parts, were discussed. The further directions of the research method in DMLS were addressed.
