Effect of carbide formation on phase equilibria and compositional modulation of transformation properties in (Mn,Fe)2(P,Si) alloys
Effect of carbide formation on phase equilibria and compositional modulation of transformation properties in (Mn,Fe)2(P,Si) alloys
复制标题
DOI：
10.1016/j.jallcom.2020.154532
复制
发表时间：
2020-02
影响因子：
6.2
通讯作者：
T. Brown;D. Galvan;J. V. Buskirk;A. Mott;P. Shamberger
中科院分区：
文献类型：
--
作者：
T. Brown;D. Galvan;J. V. Buskirk;A. Mott;P. Shamberger
要实现高效的基于磁热效应的制冷和能量转换应用，需要设计整个合金系列，在转换性能上具有狭窄的公差，因此，组件合金的组成。在有前途的磁热（Mn,Fe）2（P,Si）合金中，由于观察到几种贫P杂质相的共存，例如，增加了主四相的P含量和相变滞后损失，使得成分调整的任务变得特别困难。本文研究了Mn - Fe - P - Si体系中杂质相形成的机制，并研究了碳化物的顺序形成对观察到的相组织的影响，以及对（Mn,Fe）2（P,Si）相组成和相变性能的影响。通过定量分析测量样品中主相和杂质相的组成，我们确定(1)重复的加工步骤增加了（Mn,Fe） 9si2碳化物相的含量，导致(2)磁热学（Mn,Fe）2（P,Si）相偏离大块名义成分高达4 at。%。最后，我们绘制了(3)转变临界温度、滞后和焓与感兴趣的（Mn,Fe）2（P,Si）相组成的关系。综上所述，这些结果表明，碳杂质对（Mn,Fe）2（P,Si）合金的磁热转变性能有关键影响，因为0.3 wt %的碳含量会导致临界温度和磁滞差偏离预期设计值超过95 K和8 K。
Practical implementation of efficient magnetocaloric effect-based refrigeration and energy conversion applications requires the design of whole alloy families with narrow tolerances on the transformation properties, and therefore composition, of the component alloys. In the promising class of magnetocaloric (Mn,Fe)2(P,Si) alloys, this task of compositional tuning is made especially difficult by the observed co-existence of several P-depleted impurity phases, which for example, increases both the P content and transformation hysteresis losses of the main quaternary phase. In this work, we study the mechanisms that induce impurity phase formation in the Mn–Fe–P–Si system, and investigate the impact of sequential carbide formation on observed phase microstructure along with its effect on the composition and transformation properties of the (Mn,Fe)2(P,Si) phase. Using quantitative analyses to measure the composition within main and impurity phases in samples throughout the bulk alloy space, we establish that (1) repeated processing steps increase the content of a (Mn,Fe)9Si2carbide phase, resulting in (2) deviations in the magnetocaloric (Mn,Fe)2(P,Si) phase from bulk nominal composition of up to ∼4 at. %. Finally, we map out (3) the dependence of transformation critical temperature, hysteresis, and enthalpy on the composition of the (Mn,Fe)2(P,Si) phase of interest. Together, these results suggest carbon impurities can have a critical impact on magnetocaloric transformation properties in (Mn,Fe)2(P,Si) alloys, since 0.3 wt % carbon content can cause critical temperatures and hystereses to deviate by more than 95 K and 8 K from desired design values.