Effect of several heat treatments on the microstructure and coercivity of SmCo5 magnets

Kinetical analysis of the heat treatment procedure in SmCo5 and other rare-earth transition-metal sintered magnets

“…It has been suggested that the removal of lattice defects can be the responsible for the large increase of coercivity between sintering and heat treatment temperatures [2,3]. Even with a detailed verification of microstructure, before and after the post-sintering heat treatment in SmCo 5 [3,4,23] and NdFeB [4] magnets, no significant difference was found in microstructure, supporting the idea that the elimination of defects in atomic level can be the reason of the beneficial effect of heat treatment.…”

“…Previous microstructural studies [3,4,23] indicated that a possible microstructural change-between sintering and heat-treatment temperatures-is the elimination of rare-earth atoms from a supersatured matrix. The calculation presented in this study will take into account the experimentally measured diffusion coefficients of Sm into SmCo 5 phase [24][25][26] and the Sm-Co phase diagram [27].…”

“…V V and S V of the second phase can be determined by standard quantitative metalography techniques [31]. A typical micrograph of a SmCo 5 magnet [3,4,23] is shown in Fig. 1.The value for λ matrix measured in the sample shown in Fig.…”

“…In the case of SmCo 5 , the lower limit temperature for heat treatment is 850 • C (because the drastic decrease of coercivity under 750-800 • C, effect attributed to the eutectoid decomposition of SmCo 5 phase [23,[33][34][35]). …”

On the nature of the disordered microstructure in Sm(Co,Cu)5 alloys with increasing Cu content

“…There is still discussion on the nature of the disorder in Cu substituted SmCo 5 compounds [13][14][15][16]. While it is believed that Cu enhances the Sm solubility in the alloy driving the compound towards the Sm 2 Co 7 phase, there is also indications that disordered SmCo 7 phase can also be present in the heat treated sample.…”