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In a context where there is a continuous search for more environmentally friendly machining processes (for example, the implementation of the minimum quantity of lubrication-MQL-cooling-lubrication technique) and the constant concern with the high heat generation during the grinding process, there is still a lack of information about grinding of steel for molds and dies. Thus, the present work sought to evaluate the performance of tangential surface grinding of a steel for plastic injection molds, testing by two types of conventional abrasives (green silicon carbide and white aluminum oxide) under three different equivalent chip thicknesses. The performance of the MQL cooling-lubrication technique compared to the conventional one (flood coolant) was also evaluated. The output parameters to assess the surface integrity were the surface roughness (R a parameter), residual stresses and SEM images of the ground surfaces, as well as microhardness below the machined surface. The results shown that both conventional abrasives types have potential to be used in grinding of this steel, once low surface finish values (R a < 0.2 μm) and workpieces free of damages were fabricated. Silicon carbide (SiC) grinding wheel in general outperformed the aluminum oxide (Al 2 O 3) one in terms of surface roughness after machining under severest conditions (R a < 0.35 μm). Residual stresses were predominantly compressive irrespective of the cooling-lubrication technique and type of abrasive employed. Despite lower surface roughness and compressive residual stresses generated after grinding with the Al 2 O 3 grinding wheel, drop in hardness below the machined surface was observed, unlike when machining with SiC grinding wheel. MQL technique proved to be more effective than conventional coolant technique under the conditions investigated, irrespective of the grinding wheel used, and in some situations, it outperformed the conventional technique.

In this work, we have systematically investigated the face centered cubic (FCC) to body centered cubic (BCC) transition and its influence on hyperfine and magnetic properties of Al-substituted Fe2MnGa laminated metallic ribbons (non-annealed and annealed) prepared by arc-melting. X-ray diffraction results of non-annealed ribbons show the formation of the atomically disordered FCC (A1) phase in low Al-content (&lt;30 at. %), while a full atomically disordered BCC phase (A2) is found for high Al-content (≥50 at. %). An ordered cubic phase (L21-structure) is established in plastically deformed Al-substituted alloys annealed at 573 K for a few hours. In the L21 state, the Al content increase induces a linear reduction of the cubic cell volume, which influence s and d-electron charge and spin densities at Fe atoms. These changes are responsible for the modifications in hyperfine and magnetic properties of the studied alloys, as confirmed by first principles calculation. We have also demonstrated that the L21 state can be obtained when small percentages (5 at. %) of Al replace Ga atoms and the structural transition is basically explained by an enhancement of chemical pressure in the Al isoelectronically substituted Fe2MnGa system.

A martensitic Ni50Mn34.5In15.5 Heusler-type alloy doped with Ga was studied by x-ray diffractometry and magnetization measurements. Ga-doping does not affect the austenitic phase transition but shifts the martensitic phase transformation towards room temperature, producing an enhancement of the magnetic entropy change (ΔSM) in that temperature region. Large ΔSM-values in the Ga-doped samples are attained for an applied field of 30 kOe as opposed to the field of 50 kOe commonly found for the un-doped cases. These effects (enhancement of ΔSM-values, shift to temperatures close to 300 K, and large ΔSM-values at lower applied fields) make the Ga-doped Ni50Mn34.5In15.5 Heusler-type alloys good candidates for technological applications as a solid refrigerant.