Complete ductility in NdFeB-type alloys using the Hydrogen Ductilisation Process (HyDP)

Research output: Contribution to journalArticlepeer-review


Colleges, School and Institutes

External organisations

  • SG Technologies Limited


The work out­lined in this pa­per demon­strates sig­nif­i­cant im­prove­ments in duc­til­ity dur­ing the Hy­dro­gen Duc­til­i­sa­tion Process (HyDP) [1] of a Neo­max-type al­loy and, for the first time, com­plete duc­til­ity of a sub-sto­i­chio­met­ric al­loy. In pre­vi­ous stud­ies, the uni­for­mity of the duc­til­i­sa­tion trans­for­ma­tion was lim­ited by the pres­ence of the NdFe4B4 phase not un­der­go­ing com­plete dis­pro­por­tion­a­tion, which left ex­tremely brit­tle, mi­cron-scale is­lands in a highly duc­tile dis­pro­por­tion­ated ma­trix. The pre­sent works in­ves­ti­gated the in­flu­ence of a sig­nif­i­cantly longer (18 h) hy­dro­gen treat­ment of the Neo­max-type al­loy to ob­serve whether the com­pletely dis­pro­por­tion­ated NdFe4B4 phase is as duc­tile as the dis­pro­por­tion­ated ma­trix. It has been ob­served that, when the NdFe4B4 phase is com­pletely dis­pro­por­tion­ated, it ex­hibits sim­i­lar duc­til­ity to that of the dis­pro­por­tion­ated ma­trix, show­ing no sign of crack­ing un­der a com­pres­sive load. How­ever, in­ho­mo­gene­ity in the book mould ma­te­r­ial leads to vary­ing quan­ti­ties of NdFe4B4 phase and thus, vary­ing lev­els of dis­pro­por­tion­a­tion. De­spite this, sig­nif­i­cant im­prove­ments were ob­served in the me­chan­i­cal be­hav­iour of the Neo­max-type al­loy. The longer dis­pro­por­tion­a­tion treat­ment also re­sults in larger grains and thus, a lower fi­nal co­er­civ­ity in the re­com­bined state than that of the pre­vi­ous 5 h treat­ment. For com­par­i­son, the me­chan­i­cal be­hav­iour of a sub-sto­i­chio­met­ric al­loy, which did not con­tain any NdFe4B4 phase, has also been stud­ied. The com­pres­sion be­hav­iour of this sub-sto­i­chio­met­ric al­loy in the dis­pro­por­tion­ated state was found to be com­pletely duc­tile. It is clear from this work that it is pos­si­ble to cre­ate a com­pletely duc­tile Nd­FeB ma­te­r­ial di­rectly from the solid cast al­loy which, in the fu­ture, could have sig­nif­i­cant im­pli­ca­tions for Nd­FeB mag­net pro­duc­tion.


Original languageEnglish
Pages (from-to)268-278
JournalActa Materialia
Early online date27 Apr 2018
Publication statusPublished - 15 Aug 2018


  • Hy­dro­gen duc­til­i­sa­tion, Hard magnet, Rare earth, Phase transformation, Deformation