Microstructural stability and superplasticity in an electrodeposited nanocrystalline Ni-P alloy
Microstructural stability and superplasticity in an electrodeposited nanocrystalline Ni-P alloy
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DOI：
10.1016/j.actamat.2011.03.029
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发表时间：
2011-06
期刊：
影响因子：
9.4
通讯作者：
M. Prasad;A. Chokshi
中科院分区：
文献类型：
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作者：
M. Prasad;A. Chokshi
第二相颗粒对纳米晶晶粒尺寸的稳定有助于在高应变速率和/或低温下实现超塑性。电沉积制备的亚稳单相纳米Ni - p合金，晶粒尺寸为~ 6 nm，转变为纳米双相结构atT> 673 K，在三结处和Ni晶粒内具有~ 4 vol.%的Ni3P颗粒。在777k温度下，纳米双相结构相当稳定，Ni晶粒的生长与Ni3P晶粒的生长是耦合的，两者的平均尺寸之比(Z)基本恒定。当晶粒尺寸为290 nm时，在7 × 10−4s−1的应变速率和777k的较低温度下，合金的超塑性性能达到810%。超塑性变形促进了晶粒生长和晶粒率，表明晶界滑动对微观组织动力学有显著影响。变形过程分析表明，超塑性与位错克服晶内颗粒所控制的GBS有关，因此变形与晶粒尺寸无关。纳米ni - p合金由于高应力引起的同时空化，其延展性低于纳米ni合金。
Stabilization of nanocrystalline grain sizes by second phase particles can facilitate superplasticity at high strain rates and/or low temperatures. A metastable single phase nano-Ni–P alloy prepared by electrodeposition, with a grain size of ∼6 nm, transforms to a nanoduplex structure atT> 673 K, with ∼4 vol.% Ni3P particles at triple junctions and within Ni grains. The nanoduplex microstructure is reasonably stable up to 777 K, and the growth of Ni grains occurs in a coupled manner with the growth of Ni3P particles such that the ratio of the two mean sizes (Z) is essentially constant. High temperature tests for a grain size of 290 nm reveal superplastic behavior with an optimum elongation to failure of 810% at a strain rate of 7 × 10−4s−1and a relatively low temperature of 777 K. Superplastic deformation enhances both grain growth and the ratioZ, implying that grain boundary sliding (GBS) significantly influences the microstructural dynamics. Analysis of the deformation processes suggests that superplasticity is associated with GBS controlled by the overcoming of intragranular particles by dislocations, so that deformation is independent of the grain size. The nano-Ni–P alloy exhibits lower ductility than nano-Ni due to concurrent cavitation caused by higher stresses.