微波工程期中報告 論文 研討 : K. Saitou, “ Microwave sintering of iron, cobalt, nickel, copper and stainless steel powders ”, Scripta Materialia 54 (2006) 875–879 報告人 : 碩研電子一甲 MA 吳宗勳 Southern Taiwan University Department of Electronic Engineering

Abstract Metal powder compacts were sintered using single mode microwave radiation. The results of microwave sintering were compared with those of conventional sintering. Microwave sintering promoted greater shrinkage than conventional sintering. The sintering behavior of Fe compacts around the A3 transformation temperature was significantly affected by microwave radiation. 1 K. Saitou / Microwave sintering of iron, cobalt, nickel, copper and stainless steel powders Scripta Materialia 54 (2006) 875–879

Experimental procedure Powders were heated in an oven at 150°C in air to eliminate moisture. The powders were pressed into green compacts with dimensions of 12 mm diameter and 7.6–10 mm thick. The green compacts were sintered after the dimensions and weights were measured. Sintering was performed using two methods, MW and conventional electric furnace(EF) heating. 2 K. Saitou / Microwave sintering of iron, cobalt, nickel, copper and stainless steel powders Scripta Materialia 54 (2006) 875–879

Experimental procedure 3 Fig. 1 shows a schematic of the applicator. At first,the green compact was inserted into a boron nitride (BN) tube The MW sintering temperature was controlled manually using the calibrated pyrometer, and the heating rate was maintained at a constant 80 K/min throughout the entireMW sintering process. K. Saitou / Microwave sintering of iron, cobalt, nickel, copper and stainless steel powders Scripta Materialia 54 (2006) 875–879

4 Experimental procedure Table 1. After sintering, the density of the specimens was calculated by dimension and weight measurements, or by the Archimedesmethod. K. Saitou / Microwave sintering of iron, cobalt, nickel, copper and stainless steel powders Scripta Materialia 54 (2006) 875–879

Fig. 2 shows Arrhenius plots for the shrinkage parameters of Co, Ni, SUS 316L and Cu sintered powders. 5 Results and discussion K. Saitou / Microwave sintering of iron, cobalt, nickel, copper and stainless steel powders Scripta Materialia 54 (2006) 875–879

Fig. 3 shows an Arrhenius plot for the shrinkage of an Fe powder compact. It is widely known that Fe transforms from body-centered cubic (bcc) to face-centered cubic (fcc) at 910 °C (A3), and from fcc to bcc at 1390 °C (A 4 ), and these temperatures are indicated in Fig Results and discussion K. Saitou / Microwave sintering of iron, cobalt, nickel, copper and stainless steel powders Scripta Materialia 54 (2006) 875–879

7 Results and discussion Table. 2. shows the activation energy, Q a, calculated from Figs. 2 and 3. Activation energies for Fe are in the fccregion. Using Eq. K. Saitou / Microwave sintering of iron, cobalt, nickel, copper and stainless steel powders Scripta Materialia 54 (2006) 875–879

Except for Fe in the fcc region, MW radiation promoted the sintering of metal powders, but it did not affect the activation energy for sintering. MW radiation affected the sintering behavior of Fe around the A3 temperature. Below this temperature, MW radiation promoted sintering, but retarded sintering above this temperature. 8 Conclusion K. Saitou / Microwave sintering of iron, cobalt, nickel, copper and stainless steel powders Scripta Materialia 54 (2006) 875–879