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半固态触变成形AZ91D镁合金卫星角框件 总被引:6,自引:3,他引:3
通过对等径道角挤压处理后的AZ91D镁合金坯的触变成形试验,并借助于金相显微镜、Instron材料拉伸试验机等分析手段,对AZ91D镁合金卫星角框件的半固态触变成形工艺进行了研究。研究结果表明:当坯料加热温度为560℃,保温时间为20min,模具预热温度为400℃,保压时间为40s时,强度可达到292MPa,伸长率达到4.8%;触变成形对材料微观组织的影响主要表现为较明显的固液相分离现象,而对制件晶粒形状的影响比较小,在成形过程中,坯料的流动方式是以液相包裹球状固相颗粒的方式进行的;通过固溶处理和自然时效可以提高触变成形后的卫星角框件的强度;当固溶时间为6h,强度提高幅度在10%以上。 相似文献
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在自行设计的Couette型同轴双桶流变仪上对半固态AZ91D镁合金浆料的触变性能进行了研究,结果表明半固态AZ91D浆料经等温静置后,表观粘度升高,然后在剪切作用下逐渐降低,最后达到一个稳态值,呈现出典型的剪切变稀特性;在相同剪切速率下,随静置时间的延长,半固态AZ91D合金浆料在随后的剪切作用下表观粘度达到稳态所用时间随之延长,同时稳态表观粘度也相应增大,这主要是由于静置过程中固相颗粒发生了合并;在剪切速率和静置时间相同时,随固相率的增加,半固态AZ91D合金浆料达到稳态所需时间也随之增加;在相同固相率和静置时间下,随剪切速率的增大,半固态AZ91D合金浆料的稳态表观粘度随之降低,同时达到稳态粘度所需时间也随之减小. 相似文献
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高固相率半固态镁合金触变成形数值模拟 总被引:1,自引:0,他引:1
对高固相率半固态镁合金触变成形过程进行数值模拟,分析了成形过程中的应力、应变分布和温度场,对比了半固态坯料与常规态坯料成形的特点.结果表明,半固态镁合金材料具有变形抗力小,应力、应变分布均匀的特点,材料流动性、充填性能优于常规坯料,能够一次成形复杂形状零件.数值模拟为半固态成形工艺参数的优化起到很好的参考作用. 相似文献
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Z. H. Xiao J. R. Luo S. S. Wu D. N. Li Y. W. Mao X. J. Song 《Journal of Materials Engineering and Performance》2004,13(1):60-63
In this paper, a rheo-diecasting process of AZ91D alloy semi-solid slurry produced with a twin-screw stirring mixer was investigated.
The results show that the tensile strength and elongation of the sample made by rheo-diecasting were 37% and 44% higher, respectively,
than those produced by conventional liquid diecasting. The castings fabricated by rheo-diecasting possessed good density with
low shrinkage and could be heat treated. It is a “near-net shape” production process. 相似文献
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Thixotropic behavior of semi-solid AZ91D magnesium alloy 总被引:1,自引:0,他引:1
The thixotropie behavior of semi-solid AZ91D slurry was studied through a Couette type viseometer.The results show that the apparent viscosity of semi-solid AZ91D magnesium alloy slurry increases after being isothermally held, but the apparent viscosity quickly falls down to a steady state value after being stirred again and it takes on a sharp shear-thinning behavior. With the same shearing rate and the rest time increasing, the steady apparent viscosity increases because of the agglomeration of the solid particles, and the time required for the slurry to reach the steady state also becomes longer. If the solid fraction increases, it takes longer time for the slurry to reach the steady apparent viscosity with the same shearing rate and the same rest time. If the solid fraction and the rest time are the same, but the shearing rate rises, it takes shorter time for the slurry to reach the steady apparent viscosity and the final steady apparent viscosity also decreases. 相似文献
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Microstructure of electromagnetic stirred semi-solid AZ91D alloy 总被引:4,自引:0,他引:4
The microstructures of semi-solid AZ91D alloy stirred by rotationally electromagnetic field were studied.The shape of primary α-Mg phase is dendrite under conventional solidification condition and the primary α-Mg grains are changed to the fine rosette-like or granular grains under electromagnetic stirring condition. If the electromagnetic stirring frequencies are low, there are a large amount of fine rosette-like primary α-Mg grains and the fine rosettelike primary α-Mg grain in two dimensions belongs to a single grain in three dimensions; there are also many spherical primary α-Mg grains, they may belong to a single grain in three dimensions and the orientation differences of the grains between them are very small. If the electromagnetic stirring frequencies are high, a lot of the fine rosette-like primary α-Mg grains disappear and are converted into granular grains, and moreover, most of these granular grains belong to different grains in three dimensions. 相似文献
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Ji Ze Sheng Yan Hong Hua Zheng Xiao Ping S.O. Sugiyama J. Yanagimoto 《Journal of Materials Processing Technology》2008,202(1-3):412-418
Many complicated factors affect thixoforming fluidity in thixoforming process of semi-solid metal (SSM). So, it is important to forecast the flow property of SSM. Rigid visco-plastic constitutive model of semi-solid AZ91D Mg alloy was established at different strain rate. The thixoforming process of semi-solid AZ91D Mg alloy was simulated using commercial finite element software DEFORM-3D™. The fluid and effective stress–strain fields in the thixoforming process were obtained and the relationships among stress, strain rate and temperature also were analyzed. The thixoforming experiments were performed at 570 °C with different holding time. Finite element analysis results were compared with experimental ones, and experimental data has good agreements with the simulation results. 相似文献
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By means of equal channel angular extrusion (ECAE) test, upsetting test and metalloseope, reheating mierostruetures of raw casting ingots, materials prepared by SIMA and materials extruded by ECAE in semi-solid state were investigated. The results show that compared with those of raw casting ingots and materials prepared by SIMA, reheating microstrueture of materials extruded by ECAE is the best and the final grain size is the finest. With increasing holding time, a growing phenomenon occurs in reheating microstrueture of materials extruded by ECAE, which can be described by Ostwald ripening law. The average grain size increases firstly, subsequently decreases and the shape factor of grains approaches to 1 as the reheating temperature increases. With increasing equivalent strain, the average grain size decreases. This demonstrates that reheating material extruded by ECAE technology is a good method to prepare AZ91D magnesium alloy semi-solid billets. 相似文献
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At constant applied current, the evolution of morphology, structure and composition of anodic film on Mg alloy AZ91D with anodizing time was investigated using SEM, EDX and XRD. The development of anodic film on the Mg alloy was similar to that on high-purity Mg except that, attributed to alloying effect, hunch-like resultants replaced volcano-like ones to become predominant initial products at transitional stage of anodization. The black cicatrices at the anode surface were related with the inhomogeneous activation and dissolution under strong polarization conditions. The evolution of micropores in shape, size and number was associated with anodizing mechanism. The main elements in anodizing products were Mg, O, Al and Si, indicating that both alloy substrate and electrolyte solution were involved in anodization. Anodic film developed early was mainly comprised of periclase MgO and forsterite Mg2SiO4. However, amorphous compounds became dominant with treatment time increasing. In anodizing products, the element Al existed primarily in the form of amorphous compound. 相似文献
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应变诱发AZ91D镁合金半固态组织形态及形成机理 总被引:12,自引:2,他引:12
采用应变诱发方法制备了AZ91D镁合金半固态材料。考察了变形率、温度、保温时间对固相体积分数、组织形态以及晶粒尺寸的影响。结果表明:在冷变形条件下.于570℃保温一定时间后。可制备出固相体积分数最小达55%的镁合金半固态材料。分析讨论了AZ91D镁合金半固态组织的形成机理。在热处理过程中,组织发生再结晶,而冷变形程度对再结晶的组织有显著影响。 相似文献