热变形过程中23CrNi3Mo钢的断裂规律及数学拟合分析

通过实验和数学方法研究了23CrNi3Mo钢在不同温度下的变形规律。结果表明,23CrNi3Mo钢在800-1 200℃之间变形时,塑性良好,拉伸断口具有非常显著的塑性断裂特征。而且,减小夹杂物的数量,将会提高23CrNi3Mo钢的断裂性能。

9Cr-2W耐热合金的热变形行为及织构

通过热压缩试验研究9Cr-2W耐热合金在1000～1300℃和应变速率0.005～0.5s-1范围内的流变行为和热变形组织演变,并对热镦粗试样做了织构测定。分析该合金在实验参数范围内热变形的应力-应变特征,动力学方程,获得应力指数和变形激活能等表征其变形能力的重要特征参数。组织观察和织构测试结果表明,9Cr-2W耐热合金热变形过程中组织演变机制以动态回复和几何动态再结晶方式进行。在实际生产中,可以选择较高的变形温度来降低流变应力和改善各向异性。

Reheating and thixoforging of ZK60+RE alloy deformed by ECAE

The two-pass equal channel angular extrusion (ECAE) process was introduced into strain-induced melt activation (SIMA) to predeform a ZK60 alloy with rare earth (RE) addition. Microstructure evolution of ECAE-formed ZK60+RE alloy during reheating was investigated. Furthermore, tensile properties of thixoforged components were determined. The results show that the SIMA process can produce ideal microstructures, and spheroidized solid particles with little entrapped liquid can be obtained. With prolonging holding time, the size of solid particles increases and the degree of spheroidization is improved. The tensile properties of the thixoforged ZK60+RE samples are close to those of two-pass ECAE-formed samples.

Effects of process parameters on warpage of rapid heat cycle moulding plastic part

The effects of process parameters in rapid heat cycle moulding （RHCM） on parts warpage were investigated. A vehicle-used blue-tooth front shell （consisting of ABS material） was considered as a part example manufactured by RHCM method. The corresponding rapid heat response mould with an innovational conformal heating/cooling channel system and a dynamic mould temperature control system based on the Jll-W-160 type precise temperature controller was proposed. During heating/cooling process, the mould was able to be heated from room temperature to 160 ~C in 6 s and then cooled to 80 ~C in 22 s. The effects of processing conditions in RHCM on part warpage were investigated based on the single factor experimental method and Taguchi theory. Results reveal that the elevated mould temperature reduces unwanted freezing during the injection stage, thus improving mouldability and enhancing part quality, whereas the overheated of mould temperature will lead to defective product. The feasible mould temperature scope in RHCM should be no higher than 140 ~C, and the efficient mould temperature scope should be around the polymer heat distortion temperature. Melt temperature as well as injection pressure effects on warpage can be divided into two stages The lower stage gives a no explicit effect on warpage whereas the higher stage leads to a quasi-linear downtrend. But others affect the warpage as a V-type fluctuation, reaching to the minimum around the heat distortion temperature. Under the same mould temperature condition, the effects of process parameters on warpage decrease according to the following order, packing time, packing pressure, melt temperature, injection pressure and cooling time, respectively.

Thermal deformation analysis of the composite material satellite antenna

Controlling the thermal deformation is a crucial index for the design of the satellite antenna. To calculate and measure the satellite antenna’s thermal deformation is also an important step for the design of satellite antenna. Based on the foundation of equivalent assumption, the thermal deformation of the parabolic satellite antenna was analyzed by the finite element method for different design project. The best design project that had the minimum of the thermal deformation could be obtained through changing the lay-angle, lay-layers and lay-thickness of each layer. Results show the asymmetry structure has the minimum of thermal deformation. This paper may provide useful information for the further investigation on the coupling of thermal-stress structure.

Characterization of hot deformation behavior of Al-Zn-Mg-Mn-Zr alloy during compression at elevated temperature

The hot deformation behavior of Al-6.2Zn-0.70Mg-0.30Mn-0.17 Zr alloy and its microstructural evolution were investigated by isothermal compression test in the deformation temperature range between 623 and 773 K and the strain rate range between 0.01 and 20 s^(-1).The results show that the flow stress decreased with decreasing strain rate and increasing deformation temperature.At low deformation temperature(≤673 K) and high strain rate(≥1 s^(-1)),the main flow softening was caused by dynamic recovery;conversely,at higher deformation temperature and lower strain rate,the main flow softening was caused by dynamic recrystallization.Moreover,the slipping mechanism transformed from dislocation glide to grain boundary sliding with increasing the deformation temperature and decreasing the strain rate.According to TEM observation,numerous Al_3Zr particles precipitated in matrix,which could effectively inhibit the dynamic recrystallization of the alloy.Based on the processing map,the optimum processing conditions for experimental alloy were in deformation temperature range from 730 K to 773 K and strain rate range from 0.033 s^(-1) to 0.18 s^(-1) with the maximum efficiency of 39%.

Process Dynamics and Fractal Analysis of New Phase Formation in Thermal Processes

Boiling and fouling are taken as typical examples of new phase formation process to be analyzed and discussed in this paper. The process dynamics of nucleate boiling is analyzed and its mechanism is discussed from the view point of self-organization. Fouling, which is a more complicated phenomenon of new phase formation, involves series of underlying processes. The morphology and fractal analysis of fouling on low-energy surface and that with fouling inhibitors are studied and discussed. It is suggested that considering the process dynamics, fractal analysis and self-organization, a new avenue of research should be found.

Distortion behavior of hydro turbine blade castings during heat treatment processes under variation of seasonal temperature

Distortion often appears at the corners of heavy turbine blade castings during heat treatment processes, so a great machining allowance is generally set in production which directly results in cost increase. In this paper, a novel real-time measuring technology is developed for non-contact measuring the deformation behavior of heavy steel castings in heat treatment process. It was employed to measure the distortion and the temperature field of a batch of heavy turbine blade castings at cooling stage in normalizing process. Three inflection points appear in the distortion-time curves, and the residual distortion is affected by the regional area of not finished martensite transformation when the second inflection point appears. When the mean air temperature falls into the range of 10℃-20℃, the residual distortion is small; when it is lower than 10℃, positive distortion appears; when it is higher than 20℃, negative distortion appears. The distortion varies with seasonal temperature, which is directly responsible for the great machining allowance given in production.