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1.
Haitao Jiang Xiaoli Li Aiming Xiong Miaoquan Li 《Journal of Materials Engineering and Performance》2003,12(3):249-253
For semi-solid metal forming, it is essential to fabricate the semi-solid materials with spheroidal microstructure. Among
several fabrication techniques of the semi-solid materials, (strain-induced melt activation (SIMA) is an ideal candidate with
the advantages of simplicity and low equipment costs. In this paper, the microstructure evolution of LY11 alloy (approximately
corresponding to ASTM 2017) was investigated in the SIMA process, which had two essential stages: deformation and isothermal
heat treatment. The deformation stage was conducted using a CSS-1100C material testing machine and the isothermal heat treatment
stage was performed in a resistance furnace. Different levels of deformation temperatures, ram velocities, isothermal temperatures,
and holding times were used in this investigation. The microstructure of LY11 alloy was observed by a NEOPHOT-1 optical microscope.
The results indicated that the processing parameters must be selected properly to obtain the fine, uniform and spheroidal
microstructure by SIMA. The deformation-recrystallization mechanism for microstructure evolution in SIMA process was supported
by experimental evidence. 相似文献
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3.
Structure evolution of AZ61 magnesium alloy in SIMA process 总被引:1,自引:0,他引:1
The effect of prior compressive deformation, isothermal temperature and holding time on the structure of AZ61 magnesium alloy fabricated by strain-induced melt activation(SIMA) processing was investigated. The specimens were subjected under deformation ratios of 0%, 22% and 40% and various heat treatment time and temperature regions. The results indicate that the ideal technological parameters of semi-solid AZ61 alloy produced with non-dendrites are recommended as 22% (prior compressive deformation), 595℃ (heat treatment temperature) and 40 min(time). The as-cast AZ61 magnesium alloy isn‘t fit for semi-solid forming. 相似文献
4.
In the present article, the effect of Rare Earth elements on the microstructural development of as cast and semisolid Mg-4Al alloy produced by SIMA process is studied. Investigation conducted by metallographic observation, scanning electron microscope and quantitative metallographic methods. Results showed that alloy's dendrites turn into larger fully dendritic shape with sharp and narrow arms from equiaxed rosette type as the amount of RE elements increased from 0 through 4%. The effect of RE elements on the microstructure of the treated-alloys was detectable through elimination of vast number of intragranular liquid droplets as well as by decreasing kinetic of microstructural changes. It was shown that the trend of grain coarsening decreased drastically by addition of RE elements to the Mg-4Al alloy during partial remelting at 610 °C. Moreover, the effect of REs on the other parameters such as fraction of liquid, shape factor and particle size was studied. 相似文献
5.
1 INTORDUCTIONAlloyswithequiaxedmicrostructureexhibitsig nificantlylowerflowresistanceinthesemisolidstatethanalloyswithdendriticmicrostructure .Theirdual(thixotropic)behavior (solid likeintheunperturbedstateandliquid likeduringshearing)hasbeentheba sisfors… 相似文献
6.
研究了应变诱发熔化激活法 (SIMA)制备半固态LY11合金过程中的变形温度、变形速度、等温温度和保温时间等工艺参数对LY11合金组织演变的影响。研究结果表明 ,要获得均匀、细小的非枝晶组织 ,必须合理地匹配SIMA工艺参数 相似文献
7.
AZ91镁合金的SIMA法半固态组织特征 总被引:10,自引:0,他引:10
研究了挤压态AZ91镁合金的SIMA法半固态组织演变.结果表明:挤压合金为以α-Mg再结晶等轴晶为主相,与极少量细粒状成串分布于α-Mg基体上的Mg17Al12颗粒组成的两相组织,基体中存在大量的大角度亚晶及高密度的位错缠结.在二次加热过程中,原子扩散通道多,晶界液化及颗粒球化所需的加热温度低,等温时间短.565℃等温5min,即可获得固相率为57%,颗粒平均直径为58 μm、形状圆整、分布均匀的半固态组织.等温5 min后,半固态颗粒发生长大,其长大机制为Ostwald熟化. 相似文献
8.
The effects of compression ratios on the microstructure evolution of semisolid Al7075 alloy produced by the strain induced melt activation (SIMA) process were investigated. The samples were cold deformed by compression into the different heights up to 40% reduction. The isothermal holding treatments within mushy zone of the alloy were carried out at 610, 620 and 625 °C for predetermined time intervals.The results revealed that the average grain size gradually reduced with the increase in the compressive ratio. While the compressive ratio surpassed 30%, the descending trend above was not as evident as that of below 30% reduction. The optimum condition presenting the minimum grain size and the maximum shape factor with the highest uniformity is discussed. During the subsequent mushy zone heating, the recrystallization was induced in the deformed samples by the increasingly accumulated strain energy. 相似文献
9.
半固态坯的流动性能是获得优质、复杂制件的基础和关键。通过对两种状态合金在相同载荷作用下进行半固态压缩试验,结果表明:挤压态合金的流动性最差,挤压后冷变形态合金Ⅱ(压缩方向垂直于冷变形方向)的流动性最好。这主要有两方面的原因:一是晶粒形状上的差异;二是与半固态坯料的制备历史及其后续加工有关。 相似文献
10.
半固态坯的流动性能是获得优质、复杂制件的基础和关键。通过对两种状态合金在相同载荷作用下进行半固态压缩试验,结果表明:挤压态合金的流动性最差,挤压后冷变形态合金Ⅱ(压缩方向垂直于冷变形方向)的流动性最好。这主要有两方面的原因:一是晶粒形状上的差异;二是与半固态坯料的制备历史及其后续加工有关。 相似文献