【正文】 (d) Point D4 Conclusions1) It is feasible to produce semisolid ADC12 partsusing the gas induced semisolid process.2) The porosity and shrinkage defects in the parts can be reduced by increasing the solid fraction of the slurry.3) Good casting parts of semisolid die casting need appropriate plunger speeds and solid fractions of the slurry.4) The microstructure of the produced s。 (b) Point B。 (b) SSM11。 (b) SSM11。 (c) 15 sdie casting process is shown in . The sample consists of three overflows, a runner, and a biscuit. Most samples had plete metal filling in the overflow and good surface finish. Only the samples produced with a higher solid fraction had the cold shut defect as shown in Table 3 and the representative samples with the cold shut defect is shown in . Representative picture of die casting part Surface defect of casting: (a) Misrun。C for 12h.3) Macro defectsAll the samples were cut at the center as shown in . Next, the samples were ground with the 320, 800, and 1200 grit papers to observe the macro defects.4) Microstructure uniformityThe microstructure at different positions of the samples was observed using an optical microscope. The samples were cut and obtained from positions A, B, C, and D as shown in . The samples were then prepared for metallographic analysis using standard grinding, polishing and etching procedures. Table 2 Summary of parameters used in this study Drawing of increased rheocasting time part3 Results and discussion Semisolid slurry From the obtained results, the slurries produced by the conditions of the rheocasting times of 5, 10 and 15 s have the solid fractions of %, %, and %, respectively. The representative microstructures of the quenched samples at different rheocasting times are shown in . The micrographs illustrate that amount of the primary α (Al) (white phase) increases with increased rheocasting time. The viscosity of the slurry should be increased when the solid fraction is increased. It can be concluded that the ADC12 aluminum alloy can be produced into a semisolid slurry at a desired solid fraction by varying the rheocasting time using the GISS process. Die casting processA representative sample produced by the semisolid Representative micrographs of samples at different rheocasting times: (a) 5 s。C. The schematic diagram of the GISS die casting process is illustrated in . In this study, the porosity, surface defect, surface blister, macro and microstructure of the samples were investigated. A summary of the parameters used in this study is illustrated in Table 2. Schematic diagram of gas induced semisolid (GISS) process Schematic diagram of GISS die casting process Die casting part analysisThe analysis methods are briefly described as follows.1) Porosity analysisThe density of the sample (DL) was measured using Eq.(1), and Eq.(2) was used to calculate the porosity (η):where DS is the standard density of an ADC12 aluminum alloy ( g/cm3)。C. The times to inject the gas were 5, 10 and 15 s. The schematic diagram of the GISS process is shown in . At the varied injection times, the solid fractions were analyzed using the rapid quenching method. The high coolingrates achieved by the copper mold allow the capture of the microstructure at a certain temperature[15?16].The microstructure of the samples from different rheocasting times was used to calculate the solid fraction. The Photoshop and Image Tool Software were used in the analysis[16]. Die casting processThe aluminum slurry prepared by the GISS process was transferred to the die casting machine. This machine has 80t capacity for the clamping system. The slurry was poured into the shot sleeve kept at the temperature of 250 176。C above the liquidus temperature (~680 176。C. The eutectic temperature of this alloy is 572176。 gas induced semisolid (GISS)。C, respectively. The results show that the samples produced by the GISS die casting give little porosity, no blister and uniform microstructure. From all the results, it can be concluded that the GISS process is feasible to apply in the ADC12 aluminum die casting process. In addition, the GISS process can give improved properties such as decreased porosity and increased microstructure uniformity. Key words: ADC12 aluminum alloys。 accepted 25 June 2010AbstractThe feasibility of semisolid die casting of ADC12 aluminum alloy was studied. The effects of plunger speed, gate thickness, and solid fraction of the slurry on the defects were determined. The defects investigated are gas and shrinkage porosity. In the experiments, semisolid slurry was prepared by the gasinduced semisolid (GISS) technique. Then, the slurry was transferred to the shot sleeve and injected into the die. The die and shot sleeve temperatures were kept at 180 176。2. Department of Industrial Engineering, Faculty of Engineering, Rajamangala University of Technology Srivijaya, Songkhla, 90000, Thailand。冶金材料交易一,2005年,36:2205 2210。材料加工技術(shù),2009年,209:4537。雜志的材料加工技術(shù),2002年,122:82。[12] WANNASIN J, JUNUDOM S, TATTANOCHAIKUL T, FLEMINGM C. 氣體引起的發(fā)展過(guò)程的半固態(tài)金屬鋁壓鑄應(yīng)用[J]。日本筑波,2002:701。1996年12 04。固態(tài)現(xiàn)象,2006年,116/117:44 53。材料科學(xué)與工程,2005,412,298。冶金交易,1991年,22:957 981。紐約:施普林格,2009。材料和設(shè)計(jì),2009年,30:1169 1173。材料加工技術(shù),2006年,179:190。先進(jìn)制造技術(shù),2009年,674年44:667。牛津:ButterwortHeinemann,1991:1 85。4) 鑄造零件制作樣品的微觀結(jié)構(gòu)是全國(guó)統(tǒng)一的。(d)d點(diǎn)4總結(jié)1) 使用氣體引起的半固態(tài)工藝 生產(chǎn)半固態(tài)ADC122) 增加固態(tài)粒度的泥漿和孔隙度的收縮可以減少零件缺陷。(b)b點(diǎn)。(b)SSM11。半固態(tài)壓鑄過(guò)程中樣本的微觀結(jié)構(gòu)包括原發(fā)性a相a相結(jié)構(gòu)z在生長(zhǎng)過(guò)程中使得模具的規(guī),微觀結(jié)構(gòu)在位置A,B,C,D是 相同的模越來(lái)越大，a相共晶轉(zhuǎn)變由于冷卻速度的增大而不斷增大?？傊?找到的缺陷的起泡在半固態(tài)壓鑄可以減少增加固態(tài)粒度的大小。這種缺陷主要存在于樣品所產(chǎn)生的液體壓鑄和半固態(tài)壓鑄用的澆道口。更大的開口可以幫助減少湍流和改善供料,這減少了縮松。此外,氣體樣本中發(fā)現(xiàn)的氣孔是壓鑄生產(chǎn)的液體所產(chǎn)生的,如表3所示。圖7的孔隙度在不同條件下的樣本總之在液態(tài)鑄造中渦流的存在導(dǎo)致樣品的氣孔缺陷的產(chǎn)生相比之下,所有的半固態(tài)壓鑄的樣品比液體壓鑄中由于渦流導(dǎo)致的孔隙度低。圖7樣品孔隙度產(chǎn)生過(guò)程比較。此外,由于高固體組分凝固時(shí)間較短導(dǎo)致了冷隔缺陷的產(chǎn)生表3總結(jié)壓鑄的結(jié)果M是澆不足，C是冷隔缺陷。(b)冷隔高固體分?jǐn)?shù)引起的粘度泥漿更高。只有樣品和較高的固態(tài)粒度有冷隔缺陷如表3所示,代表樣本與冷隔缺陷顯示在圖7。(c)15秒壓鑄過(guò)程如圖5所示示例包括三個(gè)溢流槽,澆道,和一個(gè)手柄。一個(gè)代表性樣本所產(chǎn)生的半固態(tài)圖4代表顯微組織