Compression of semi-solid dendritic Sn-Pb alloys at low strain rates
Compression of semi-solid dendritic Sn-Pb alloys at low strain rates
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低应变率下半固态枝晶 Sn-Pb 合金的压缩
DOI：
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发表时间：
1984
期刊：
影响因子：
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通讯作者：
M. Flemings
中科院分区：
文献类型：
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作者：
D. Pinsky;P. O. Charreyron;M. Flemings
研究了半固态枝晶Sn-Pb合金在共晶以上一度的行为。在平行板装置中以1.3 x 10−2 s−1的初始应变速率对小圆柱形样品进行变形。发现样品和板之间的摩擦强烈地影响材料的压缩强度和由此产生的液-固偏析。对于低摩擦，最大应力发生在约0.3的应变处。在此应变以上，观察到大裂纹。高摩擦导致比低摩擦观察到的更高程度的偏析。没有观察到最大应力和裂纹，即使对于高摩擦的应变大至1.2。圆柱形样品通过圆柱形模具以8.5 X 1075 ms-1至8.5 X 1074 ms-1的恒定活塞速度挤出，并且面积减小率为2：1至8：1。变形以两种不同的模式发生。第一种是“压实”模式，在此期间，在增加的应力下，液体被排出，固体被压实但不流过模具。第二种是“流动挤压”模式，在此模式下，压实的固体在恒定应力σrextr下流过模具，发现σrextr与面积减少的自然对数成正比。实验涉及压缩过滤器和压缩之间的平行板的合金的不同组成进行检查的馏分液体的半固态树枝状合金的流变性的影响。变形所需的应力被认为表现出相同的伪塑性应变率依赖平行板，活塞过滤器和在正向挤压实验。这种应变率依赖性可以用幂律表达式来概括：σ ε = 0.23。
The behavior of semi-solid dendritic Sn-Pb alloys was studied at one degree above the eutectic. Small cylindrical samples were deformed at an initial strain rate of 1.3 x 10−2 s−1 in a parallel-plate apparatus. The friction between the sample and the plates was found to affect strongly both the strength of the material in compression and the resultant liquid-solid segregation. For low friction a maximum stress occurred at strains of about 0.3. Above this strain large cracks were observed. High friction resulted in a much higher degree of segregation than observed for low friction. No maximum stress and no cracking was observed, even for strains as large as 1.2 for high friction. Cylindrical samples were extruded through cylindrical dies at constant piston velocities ranging from 8.5 x 10≓5 ms~’ to 8.5 X 10≓4 ms≓1, and with reduction of area ranging from 2:1 to 8:1. The deformation occurred in two distinct modes. First, a “compaction≓ mode, during which liquid was expelled and the solid compacted but did not flow through the die, under increasing stress. Second, a “flow≓ mode, during which compacted solid flowed through the die, under a constant stress, σrextr, which was found to be proportional to the natural logarithm of the area reduction. Experiments involving compression over a filter and compression between parallel plates of alloys of different compositions were performed to examine the effects of the fraction liquid on the rheology of semi-solid dendritic alloys. The stress required for deformation was seen to exhibit the same pseudo-plastic strain-rate dependence for parallel plate, piston-filter and in forward extrusion experiments. This strain-rate dependence can be summarized by the power-law expression: σ ∝ ɛ0.23.