PDF《Trans. Nonferrous Met. Soc. China》

Nanoperm'

alloys in

1990 [10], '

Hitperm'

alloys in

1998 [11], iron core materials for transformer with super lower iron loss in Japan in

2000 [12], and bulk '

Liqualloy'

high performance soft magnetic sheet alloy in Japanese Alps Electrics Co., Ltd. Foundation item: Project (13961001D) supported by the Key Basic Research Project of Hebei Province, China;

Project (2013BAE08B01) supported by the National Key Technology R&

D Program of China Corresponding author: Qiang LI;

Tel: +86-335-8063946;

E-mail: [email protected] DOI: 10.1016/S1003-6326(14)63115-0 Xing-hua WANG, et al/Trans. Nonferrous Met. Soc. China 24(2014) 712?717

713 in

2011 [13]. However, the shapes of the above alloys prepared by rapid quenching techniques were primary ribbon and sheet so that they could not satisfy the demand for complicated shape in industrial application. So development of Fe-based bulk nanocrystalline composites by simple process, low cost, complicated shape and superior soft magnetic properties has a broad application prospect. In this work, bulk amorphous and nanocrystalline Fe75Zr3Si13B9 composites were fabricated by mechanical alloying and spark plasma sintering. The sintering characteristics and the influence of sintering temperature on microstructure, mechanical properties and magnetism were investigated.

2 Experimental Pure elemental powders of Fe (purity≥99.5%, 5?8 μm), Zr (purity≥99.9%,

38 μm), Si (purity≥99.99%,

48 μm) and B (purity≥99.99%,

48 μm) were mixed to the desired nominal composition of Fe75Zr3Si13B9, in stainless steel vessels with stainless steel balls, and the ball to powder mass ratio was 30:1. In order to avoid the oxidation of the mixed powders, the vessels were extracted and filled with high purity Ar gas (99.99%). Mechanical alloying was performed by a high-energy planetary ball mill (QM-3SP4) at a rotational speed of

450 r/min. The milling process was periodically interrupted every 0.5 h and each interruption was lasted 0.25 h to cool down the vessels. The as-milled powders were weighed

10 g and put into the WC hard metal mold, which had two WC hard metal punches with diameter of

20 mm. Then the powders were sintered with SPS equipment (SPS-3.20MK-IV) under a pressure of

500 MPa, at a heating rate of

30 K/min, with holding time of

10 min. The bulk amorphous and nanocrystalline Fe75Zr3Si13B9 magnetic alloys with a diameter of

20 mm and height of

7 mm were fabricated at different sintering temperatures, which were measured by the thermocouple. The structures of the as-milled powders and the sintered samples were examined by X-ray diffractometry (XRD) equipment of type D/max?2500 with Cu Kα radiation. Thermal behaviors of the as-milled powders were measured with a differential scanning calorimeter (DSC, NETZSCH STA449C) at a heating rate of

30 K/min under flowing Ar gas (99.99%), and the different sintering temperatures (Ts) were selected based on the DSC results. The microstructures of the samples sintered at different temperatures were observed with scanning electron microscope (SEM, HITACHI S?4800). The density was measured by Archimedes drainage method. The compressive strength was examined with a Gleeble?3500. The microhardness was tested with a microhardness tester (FM-ARS?9000) at a load of 2.94 N with

10 s dwell time. Magnetic properties including saturation magnetization (Bs) and coercive force (Hc) were measured with vibrating sample magnetometer (VSM, Lakeshore 7404) in a maximum applied magnetic field of