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湘潭大學(xué)興湘學(xué)院
畢業(yè)論文（設(shè)計(jì)）任務(wù)書
論文（設(shè)計(jì)）題目：自行車用無級(jí)變速器結(jié)構(gòu)設(shè)計(jì)
學(xué)號(hào)： 2010963142 姓名： 朱楊華 專業(yè)： 機(jī)械設(shè)計(jì)制造及其自動(dòng)化
指導(dǎo)教師： 聶松輝 系主任：
一、主要內(nèi)容及基本要求
1、輸入功率P=0.15kw、最低轉(zhuǎn)速n=20rpm、調(diào)速范圍R=8；
2、裝配圖A0#1張、零部件圖總量不小于A0#1張；
3、設(shè)計(jì)說明書一份（含電子文檔）；
4、英文文獻(xiàn)翻譯資料一份，不少于3000Words。
二、重點(diǎn)研究的問題
1、機(jī)械式無級(jí)變速器的變速原理；
2、基于變速原理的傳動(dòng)結(jié)構(gòu)實(shí)現(xiàn)。
三、進(jìn)度安排
各階段完成的內(nèi)容
起止時(shí)間
1
熟悉課題與基礎(chǔ)資料
第1周
2
調(diào)研、收集資料
第2周
3
方案設(shè)計(jì)與論證
第3～4周
4
無級(jí)變速器各零件三維模型設(shè)計(jì)
第5～7周
5
無級(jí)變速器總裝配圖設(shè)計(jì)
第8周
6
無級(jí)變速器工程圖設(shè)計(jì)
第9周
7
無級(jí)變速器關(guān)鍵部件運(yùn)動(dòng)仿真
第10周
8
撰寫設(shè)計(jì)說明書
第11周
9
英文文獻(xiàn)翻譯\答辯
第12周
四、應(yīng)收集的資料及主要參考文獻(xiàn)
應(yīng)收集的資料：自行車無級(jí)變速器的類型和無級(jí)變速自行車的研究現(xiàn)狀，零件的設(shè)計(jì)與計(jì)算的方法，以及選型等。
主要參考文獻(xiàn)：
[1] 周有強(qiáng). 機(jī)械無級(jí)變速器[M]. 成都:機(jī)械工業(yè)出版社,2001.
[2] 阮忠唐.機(jī)械無級(jí)變速器設(shè)計(jì)與選用指南[M].北京:化學(xué)工業(yè)出版社，1999.
外文翻譯
半固態(tài)成型：
競(jìng)爭(zhēng)來自汽車復(fù)雜零件的鍛造機(jī)
Q. ZHU1, S. P. MIDSON2
1.英國(guó)康明斯渦輪增壓技術(shù)有限公司，圣安得烈路，哈德斯菲爾德，Hd1 6RA S；
2.美國(guó)鋁復(fù)雜組分公司，科羅拉多州丹佛賈森街道2211南，80223， 2010年5月13日收到; 2010年6月25日接受
摘 要
葉輪制造的最新技術(shù)被稱為半固態(tài)成型（SSM）。它是康明斯渦輪增壓技術(shù)有限公司與鋁復(fù)合元件公司一起開發(fā)，SSM壓縮機(jī)輪的一種方式。它能使鑄造和加工固體之間（MFS）鋁合金車輪，實(shí)現(xiàn)成本和耐久性的地方。實(shí)驗(yàn)結(jié)果表明，SSM材料具有優(yōu)良的顯微組織和力學(xué)性能，這些都高于MFS材料。測(cè)試包括耐久性的組分測(cè)試，使用加速的速度周期測(cè)試，證明SSM壓縮機(jī)輪子比鑄造的等值更耐用和接近MFS葉輪。為了使半固態(tài)處理進(jìn)一步挑戰(zhàn)of other complex components and other materials in automotive industry in terms of both cost and durability are also discussed.，對(duì)汽車行業(yè)中制造成本和其他成分復(fù)雜等材料的耐久性進(jìn)行了討論。
關(guān)鍵詞： 鋁合金; 半固體造型; 耐久性; 汽車復(fù)雜組分; 蒸氣增壓器壓縮機(jī)輪子
1引言
柴油和汽油發(fā)動(dòng)機(jī)是造成的排放和全球變暖的一個(gè)重要來源。為了提高燃油效率和減少排放，汽車輕量化是一種有效的方法.。半固態(tài)成型（SSM）已成功幫助，減輕汽車零部件的重量，明顯改善的機(jī)械性能。所以，可以用小或更薄的壁零件。汽車零部件已成功用SSM。達(dá)斯古普塔[ 1 ]總結(jié)了最普遍的應(yīng)用如下： 1) A357-T5,2)自動(dòng)傳輸使換中檔杠桿A357-T5， 3)發(fā)動(dòng)機(jī)裝配A357-T5， 4)引擎托架1 800 g A357-T5， 5)上部控制臂A356-T6， 6)懸浮A357-T5， 7)引擎托架720 g A357-T5， 8)引擎托架2400 g A357-T5和9)柴油引擎A356- T5泵體加油路軌。
發(fā)動(dòng)機(jī)技術(shù)發(fā)展的另一種有效的提高燃油效率和減少排放。增加氣壓比率到發(fā)動(dòng)機(jī)方式能夠進(jìn)一步提高燃油效率和減少排放的目的。增加氣壓可以通過在一個(gè)渦輪增壓器壓縮機(jī)輪來實(shí)現(xiàn)。壓縮機(jī)輪需要非常復(fù)雜的葉片，幾何實(shí)現(xiàn)高壓力比。應(yīng)付250 °C和重大溫度差時(shí)，壓縮機(jī)輪承受的旋轉(zhuǎn)速度高達(dá)200 000轉(zhuǎn)/分鐘。除機(jī)械力量和溫度能力的要求之外，由于在速度周期上的刀片的變化和振動(dòng)，疲勞是一種典型的失效模式。
這種組合的復(fù)雜的幾何形狀和堅(jiān)韌操作條件,意味著調(diào)制解調(diào)器壓縮機(jī)輪子要求最佳的物質(zhì)技術(shù)。幾十年來，壓縮機(jī)的車輪含有鋁，硅和銅的合金。要達(dá)到指定的耐久性目標(biāo)，然而，制約他們的發(fā)行速度，即是必要的。由于鑄造缺陷，在操作過程中減少了發(fā)動(dòng)機(jī)的效率。因此，固體(MFS)或鍛件壓縮機(jī)輪子的開發(fā)，克服鑄件瑕疵問題。在耐久性的改善也意味MFS輪子可能可靠地跑以更高的速度，增長(zhǎng)的燃料效率和減少排放。缺點(diǎn)是MFS鑄造比較昂貴。
因此，半固態(tài)成形加工（SSM）應(yīng)用開發(fā)的制造過程中，在鑄造和MFS鋁合金之間車輪，去實(shí)現(xiàn)成本和耐久性能。由于壓縮機(jī)輪幾何形狀復(fù)雜，精度控制的要求和嚴(yán)格的操作條件，制造壓縮機(jī)輪可能是SSM最困難的過程。在這項(xiàng)工作SSM應(yīng)用的開發(fā)和結(jié)果在制造業(yè)壓縮機(jī)輪子在復(fù)雜幾何學(xué)汽車組分制造被提出，為例SSM應(yīng)用。
2 渦輪增壓
最近渦輪增壓技術(shù)廣泛用于柴油發(fā)動(dòng)機(jī)和汽油發(fā)動(dòng)機(jī)，直接噴射技術(shù)也一起發(fā)展。對(duì)于新汽車渦輪增壓器的應(yīng)用量（合適的）。如圖1所示，在過去10年1999年-2004年穩(wěn)定增長(zhǎng)約10%和2004年-2009年約5%，平均年增長(zhǎng)率約7%。在2004年-2009年較低的增長(zhǎng)率，主要是由經(jīng)濟(jì)衰退引起的。自2008年以來，未來10年預(yù)計(jì)年增長(zhǎng)率將有約8%。2007年蒸氣增壓器新車的世界總寬容量大約是20百萬個(gè)單位，相當(dāng)于6.8十億USD。
圖1 全球渦輪增壓發(fā)動(dòng)機(jī)市場(chǎng)（首次適應(yīng)卷）
渦輪增壓器可以通過壓縮機(jī)輪子有效地增加氣壓，這是由通過廢氣渦輪軸排氣。圖2顯示了一個(gè)典型的廢氣旁通增壓器。壓縮機(jī)輪子的轉(zhuǎn)動(dòng)速度可高達(dá)200 000 r/min。進(jìn)一步增加的速度是提高效率和燃油經(jīng)濟(jì)性。然而，轉(zhuǎn)動(dòng)速度由壓縮機(jī)和渦輪葉輪的材料物產(chǎn)生限制。渦輪增壓器故障主要是由壓縮機(jī)或渦輪機(jī)在高溫條件下引起疲勞。
圖2典型的廢氣旁通增壓器概述
3 SMM制造渦輪增壓器壓縮機(jī)輪的挑戰(zhàn)
渦輪增壓器壓氣機(jī)葉輪幾何的設(shè)計(jì)是非常復(fù)雜，為了滿足特定的效率和耐久性的要求。圖3給出了一個(gè)典型的壓縮機(jī)葉輪的設(shè)計(jì)。葉片長(zhǎng)度與葉片厚度比約為25，這使得它在SSM難填補(bǔ)的葉片和中央集線器刀片的質(zhì)量比可以達(dá)到80左右，同時(shí)這使得它很難獲得滿意的葉片和輪轂組織。此外，葉片的曲度在處理以后SSM模子難拆卸。因此，模具設(shè)計(jì)，澆注系統(tǒng)設(shè)計(jì)及模具溫度控制和流道系統(tǒng)是達(dá)到一個(gè)成功的結(jié)果的關(guān)鍵參量[2]。另外，材料也必須經(jīng)過仔細(xì)挑選，以滿足在嚴(yán)格操作條件下符合壓縮機(jī)輪子的耐久性的嚴(yán)密要求。
圖3概述（a）、剖面圖（b）典型的壓縮機(jī)w heel砂輪
4 材料的選擇
材料的選擇是決定開始的物理性能如熱導(dǎo)率，熱系數(shù)和合金密度保證當(dāng)前組分設(shè)計(jì)有效性。認(rèn)為3XX鑄造鋁合金可用于目前壓縮機(jī)輪的設(shè)計(jì)。可用所有[ 3-33 ] 數(shù)據(jù)的SSM的力學(xué)性能和鑄鋁合金比較后，319s合金被選擇制造壓縮機(jī)輪子。圖4顯示319s合金具有合理最好的和一致的拉伸強(qiáng)度和伸長(zhǎng)率。從純粹的拉伸性能的觀點(diǎn)，SSM A201也顯示了可喜的成果。因此，SSM A201試驗(yàn)，更好的實(shí)現(xiàn)了文學(xué)強(qiáng)度和延性比。然而，SSM A201沒有市售的。所以用于制造壓縮機(jī)輪仍然是SSM 319s合金。
圖4 SSM鋁合金的拉伸性能比較永久模鑄造的（PM）
5 結(jié)果
在表1中給出了SSM壓縮機(jī)輪選擇合金319s化學(xué)成分。圖5顯示SSM 319s壓縮機(jī)輪有優(yōu)越的抗拉伸強(qiáng)度和延展性。在2618鍛造熱處理T61的條件下用于壓縮機(jī)輪的c355和目前354接近。單軸疲勞試驗(yàn)結(jié)果表明，試樣從一個(gè)平行的方向鍛造2618合金的金屬流動(dòng)具有優(yōu)良的耐疲勞性，而在垂直方向有類似的疲勞性能抵抗熔鑄355（6）。金屬化流程樣品的取向之間這個(gè)區(qū)別主要出現(xiàn)從粗第二個(gè)階段微粒的對(duì)準(zhǔn)線。改善疲勞在圖6小應(yīng)變中可以看到SSM 319s在鑄造355的屬性。如圖7所示，已被證明組件的磁盤疲勞試驗(yàn)，是由單軸的壓縮應(yīng)力與R> O在從壓縮機(jī)輪子的后面面孔用機(jī)器制造的盤樣品進(jìn)行。在渦輪增壓器組件測(cè)試中，檢測(cè)的細(xì)胞受康明斯渦輪增壓技術(shù)的限制，結(jié)果列于圖8。圖8顯示了鑄造c355，2618和SSM 319s相比的耐久性。SSM 319s和偽造2618壓縮機(jī)輪之間，雖然他們都優(yōu)越鑄造c355的耐久性。SSM 319s和偽造的2618的這重大改善主要來自材料的改善和鑄件瑕疵的排除，例如氧化物。除對(duì)材料的完整性，鍛造和SSM的改進(jìn)清潔。鍛造2618和SSM 319s比鑄造的C355和354.0的晶粒結(jié)構(gòu)細(xì)化和顯微組織是對(duì)壓縮機(jī)輪子的耐久性改善的另一貢獻(xiàn)(圖9)。
圖5顯示了SSM 319s鑄造優(yōu)越的抗拉性能C355, 354.0 and 319 while comparable with forged 2618c355，354和319，與鍛造2618
圖6通過鑄造SSM 319s顯示出c355與鍛造2618優(yōu)越的耐疲勞性
圖7 SSM 319s顯示出在鑄造c355阻力優(yōu)越的單軸疲勞resistance over cast C355
圖8 SSM 319s壓縮機(jī)輪表現(xiàn)出在鑄造c355壓縮機(jī)輪與forged 2618鍛造2618優(yōu)越的耐久性
圖9晶粒結(jié)構(gòu)的鑄造c355（a），2618（b）和鍛造SSM 319s (c), indicating comparable grain size between forgedSSM 319s（c），表明類似的晶粒尺寸之間鍛造and SSM alloys, while both significant finer than cast alloy和SSM合金，而顯著小于鑄造合金。
5 執(zhí)行總結(jié)
1）渦輪增壓是實(shí)現(xiàn)大幅減排和燃油經(jīng)濟(jì)一個(gè)最成功的技術(shù)。渦輪增壓發(fā)動(dòng)機(jī)在過去10年已經(jīng)取得大約7%的體積增加，并且未來10年預(yù)測(cè)增長(zhǎng)8%。
2）SSM已被成功地應(yīng)用于生產(chǎn)極其復(fù)雜的幾何渦輪增壓器的壓縮機(jī)車輪。
3）SSM壓縮機(jī)輪取得了拉伸，疲勞性能和部件的耐久性。所以，它接近2618鍛造，優(yōu)于鑄造c355。
6 未來的挑戰(zhàn)
雖然制造業(yè)的SSM汽車零部件已取得重大進(jìn)展，研究人員努力開發(fā)新的合金和工藝，仍有需要更多的努力來滿足工業(yè)要求。這些措施包括：
1）更多選擇的合金
有汽車的工業(yè)應(yīng)用不同要求，一些需要高強(qiáng)度，而有些人可能需要高的熱性能，疲勞性，耐腐蝕性和耐磨性。這些都需要不同的合金系統(tǒng)滿足一個(gè)或多個(gè)工業(yè)應(yīng)用的要求。
2）高熔點(diǎn)合金系統(tǒng)
發(fā)展SSM是最大的努力過程歷史上以相對(duì)較低的熔化點(diǎn)、合金如鋁和鎂合金。一些努力和成功取得了高熔點(diǎn)點(diǎn)合金如鋼[ 34 ]，但進(jìn)一步的研究需要發(fā)展的材料系統(tǒng)的鑄鐵，鋼鎳基合金。這些材料具有顯著的比鋁和鎂合金密度更高，所以有更大的潛在節(jié)省更多的重量汽車零部件，從而更多的燃油經(jīng)濟(jì)性，和提高質(zhì)量和性能，耐久性在SSM過程改進(jìn)的光比合金。
3）復(fù)雜的幾何部件
一些汽車零部件的復(fù)雜幾何，例如一個(gè)渦輪增壓器壓氣機(jī)輪和發(fā)動(dòng)機(jī)缸頭，使得它很難實(shí)現(xiàn)嚴(yán)格的性能要求，在鑄造鍛坯加工效率/成本。因此，SSM幾何組成有制造復(fù)雜的巨大潛力。非常低的剪切強(qiáng)度在半固態(tài)狀態(tài)合金使它實(shí)現(xiàn)制造復(fù)雜的幾何部件時(shí)澆注系統(tǒng)的合理設(shè)計(jì)與模具結(jié)構(gòu)在低剪切強(qiáng)度達(dá)到可容納相對(duì)較高的抗壓強(qiáng)度。
4）還原電流SSM元件成本
在使用SSM加工過程中減少零件的制造成本實(shí)現(xiàn)鍛坯。然而，由于成本高制造原料棒料，復(fù)雜性澆注系統(tǒng)和模具結(jié)構(gòu)以及相對(duì)高成本，SSM組件的成本仍然顯著高于鑄造。因此，應(yīng)作出努力，進(jìn)一步達(dá)到降低成本棒料的原材料，設(shè)計(jì)和制造澆注系統(tǒng)和模具結(jié)構(gòu)和工藝。
致謝
作者想表達(dá)他們的感謝，在康明斯渦輪增壓邁克爾鳳博士對(duì)批判性閱讀和科技有限公司本文的評(píng)論。多虧了安得烈.杰克遜的鋁成分復(fù)雜，開發(fā)工具和一般支持successfully manufacturing the SSM impelle成功地生產(chǎn)的SSM葉輪。
參考文獻(xiàn)
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Semi-solid moulding: Competition to cast and machine from forging in making automotive complex components Q. ZHU 1 , S. P. MIDSON 2 1. Cummins Turbo Technologies Limited, St. Andrews Road, Huddersfield, HD1 6RA, UK; 2. Aluminium Complex Components Inc, 2211 South Jason Street, Denver, Colorado 80223, USA Received 13 May 2010; accepted 25 June 2010 Abstract： The very latest technique for impeller manufacture is called semi-solid moulding (SSM). Cummins Turbo Technologies Limited, together with Aluminum Complex Components Inc, developed SSM compressor wheels as a way of achieving cost and durability performance somewhere between that of cast and machined from solid (MFS) aluminium alloy wheels. Experimental results show SSM material has a superior microstructure and mechanical properties over cast and comparable to MFS materials. Component testing including durability testing, using accelerated speed cycle tests, proves SSM compressor wheels emerge as being significantly more durable than cast equivalents and approaching that of MFS impellers. Further challenges for semi-solid processing in manufacture of other complex components and other materials in automotive industry in terms of both cost and durability are also discussed. Key words: aluminum alloys; semi-solid moulding; durability; automotive complex component; turbocharger compressor wheel 1 Introduction Diesel and gasoline engines are one of the most important sources to cause emission and global warming. To increase fuel efficiency and to reduce emission, vehicle weight reduction is one of the effective ways. Semi-solid moulding (SSM) has successfully helped to reduce weight of automotive components due to the significant improvement of mechanical properties over cast, so, smaller or thinner wall parts can be used. Automotive components have been successfully manufactured by SSM. DASGUPTA1 has summarized the most popular applications as: 1) fuel rail of A357-T5, 2) automatic transmission gear shift lever of A357-T5, 3) engine mount of A357-T5, 4) engine bracket 1 800 g of A357-T5, 5) upper control arm of A356-T6, 6) suspension of A357-T5, 7) engine bracket 720 g of A357-T5, 8) engine bracket 2 400 g of A357-T5, and 9) diesel engine pump body of A356-T5. Engine technology development is another effective way increasing fuel efficiency and to reduce emission. Increasing the air pressure ratio to the engine is a way to achieve the objective of further improving fuel efficiency and reducing emission. One way to increase air pressure can be achieved by a compressor wheel in a turbocharger. The compressor wheel needs very complex blade geometry to achieve high pressure ratios. Compressor wheel withstands rotational speeds up to 200 000 r/min but must do so while coping with up to 250 C and a significant temperature gradient. In addition to the requirements of mechanical strength and temperature capability, fatigue is a typical failure mode of a compressor wheel in application due to changes in speed cycles and vibration of blades. This combination of sophisticated geometry and tough operating conditions means that the modern compressor wheels demand the best material technology. Compressor wheels for decades have been cast from alloys containing aluminum, silicon and copper. To achieve the specified durability targets, however, it is necessary to restrict their release speed, i.e. to reduce efficiency of an engine during operation due to cast defects. Therefore, the machined from solid (MFS) or forging compressor wheels have been developed to overcome the casting defect problem. The improvement in durability also means MFS wheel can run reliably at the higher speeds, increasing fuel efficiency and reducing emission. The downside is that MFS is significantly more expensive than casting. Therefore, semi-solid moulding (SSM) processing is applied to develop a manufacturing process that is a Corresponding author: Q. ZHU; +44-1484-832567; E-mail: Qiang.zhuC; Q Trans. Nonferrous Met. Soc. China 20(2010) s1042-s1047 Q. ZHU, et al/Trans. Nonferrous Met. Soc. China 20(2010) s1042-s1047 s1043 way of achieving cost and durability performance somewhere between that of cast and MFS aluminum alloy wheels. Due to the complex geometry, precision control requirement and severe operation condition of a compressor wheel, manufacturing compressor wheel may be one of the most difficult processes for SSM. In this work, development and results of SSM application in manufacturing compressor wheels are presented, as an example of SSM application in manufacture of complex geometric automotive components. 2 Turbocharging Turbocharging technology is widely used for diesel engine and recently also for gasoline engine together with direct injection technology development. The volume of turbocharger application for new vehicles (first fit) has steadily increased by about 10% between 1999 and 2004 and 5% between 2004 and 2009, leading to about 7% average annual increase rate in the past 10 years (Fig.1). The lower increase rate between 2004 and 2009 has been mainly caused by the economic recession since 2008 and it is expected that annual increase rate in the next 10 years will be about 8%. The total world wide volume of turbochargers in 2007 was about 20 million units for new vehicles, which was equivalent to 6.8 billion USD. Fig.1 Global turbocharged engine market (first fit volume) Turbocharger can effectively increase air pressure ratio through a compressor wheel, which is driven by turbine wheel through a shaft by exhaust gas. Fig.2 shows a typical wastegated turbocharger. The speed of rotation of the compressor wheel can reach as high as 200 000 r/min. Further increasing speed is desirable for improved efficiency and fuel economy. However, the rotation speed is limited by materials properties of the compressor and turbine wheels. Failure of a turbocharger is mainly caused by fatigue of the compressor or turbine wheel operated at high temperatures. Fig.2 Overview of typical wastegated turbocharger 3 Challenges of manufacturing turbocharger compressor wheels by SSM The geometry of a turbocharger compressor wheel is designed to be very complex in order to meet specific efficiency and durability requirement. Fig.3 presents a typical design of a compressor wheel. The ratio of blade length to blade thickness is about 25, which makes it difficult to fill the blade during SSM process, and the ratio of mass at central hub to blade can be about 80, which makes it difficult to get satisfied microstructure for both blade and hub simultaneously. In addition, the curvature of the blades makes it difficult to disassemble the SSM die after processing. Therefore, die design, runner system design and temperature control of the die and runner system are the key parameters to achieve a successful result2. In addition, materials must be also selected very carefully to meet the stringent requirements of durability of a compressor wheel under the severe operation conditions. Fig.3 Overview (a) and section view (b) of typical compressor wheel Q. ZHU, et al/Trans. Nonferrous Met. Soc. China 20(2010) s1042-s1047 s1044 4 Materials selection Materials selection was started from determining the physical properties such as thermal conductivity, thermal coefficient and alloy density to ensure the validity of current component design. It was recognized that all 3XX cast aluminum alloys can be applied for currently designed compressor wheels. After comparison of all available data3-33 of mechanical properties for SSM and cast aluminum alloys, the 319s alloy was selected to manufacture compressor wheels. Fig.4 shows that SSM 319s alloy has reasonably the best and consistent tensile strength and elongation. From purely tensile property point of view, SSM A201 also shows promising results and therefore, trials were also conducted. Better strength and comparable ductility of SSM A201 than those in literature was achieved. However, SSM A201 was not commercially available so SSM 319s was still the alloy used to manufacture compressor wheels. Fig.4 Tensile properties of SSM aluminum alloys compared with permanent mould (PM) cast ones 5 Results Chemical composition of the selected alloy 319s for SSM compressor wheel is given in Table 1. Fig.5 shows that the SSM 319s compressor wheel had superior tensile strength and ductility over cast C355 and 354.0 currently used on compressor wheels and approaching those of the forged 2618 under the condition of heat treatment T61. Uniaxial fatigue testing results showed that samples cut from forged 2618 alloy in a parallel direction to the metal flow had superior fatigue resistance whereas in the perpendicular direction it had similar fatigue resistance to cast 355 (Fig.6). This difference between orientations of sample to metal flow mainly arises from the alignment of coarse second phase particles. Improvement of fatigue property of SSM 319s over cast 355 can also be seen at Table 1 Chemical composition of 319s (mass fraction, %) Element Min. Max. Copper (Cu) 2.0 3.0 Magnesium (Mg) 0.25 0.35 Silicon (Si) 5.0 6.0 Iron (Fe) 0.15 Nickel (Ni) 0.03 Zinc (Zn) 0.05 Titanium (Ti) 0.20 Manganese (Mn) 0.03 Lead+Tin (Pb+Sn) 0.05 Strontium (Sr) 0.01 0.05 Others (Each) 0.03 Others (Total) 0.1 Aluminium (Al) Bal. Fig.5 SSM 319s showing superior tensile properties over cast C355, 354.0 and 319 while comparable with forged 2618 Fig.6 SSM 319s showing superior fatigue resistance over cast C355 while comparable with forged 2618 small strains in Fig.6. This has been proven by component disk fatigue test, where uniaxial compressive stress with R0 on the disk samples machined from back face of compressor wheel was performed, as shown in Fig.7. Component testing in a turbocharger was carried out on gas stand testing cells at Cummins Turbo Technologies Limited and the results are given in Fig.8. Q. ZHU, et al/Trans. Nonferrous Met. Soc. China 20(2010) s1042-s1047 s1045 Life comparison between cast C355, forged 2618 and SSM 319s in Fig.8 shows a comparable durability between SSM 319s and forged 2618 compressor wheels, while they both have superior durability over cast C355. This significant improvement of SSM 319s and forged 2618 arises mainly from improvement of material integrity and the elimination of casting defect such as oxides. In addition to the material integrity and cleanliness improvement by forging and SSM, refinement of grain structure and thus microstructure of forged 2618 and SSM 319s compared with cast C355 and 354.0 is another contribution to the durability improvement of compressor wheels (Fig.9). Fig.7 SSM 319s showing superior component uniaxial fatigue resistance over cast C355 Fig.8 SSM 319s compressor wheel showing superior durability over cast C355 compressor wheel while comparable with forged 2618 5 Executive summary 1) Turbocharging is one of the most successful technologies to achieve significant emission reduction and fuel economy. About 7% volume increase of turbocharged engines has been achieved in the past 10 years and 8% increase in the next 10 years is predicated. 2) SSM has been successfully applied to produce extremely complex geometric turbocharger compressor wheels. Fig.9 Grains structure of cast C355 (a), forged 2618 (b) and SSM 319s (c), indicating comparable grain size between forged and SSM alloys, while both significant finer than cast alloy 3) SSM compressor wheel has achieved tensile and fatigue properties, and so component durability, approaching forged 2618 and superior over cast C355. 6 Future challenges Although significant progress of manufacturing automotive components by SSM has been achieved and extensive efforts to develop new alloys and processes have been made by researchers, there are still needs for more efforts to satisfy requirements from the industry. These include: 1) More choices of alloys There are different requirements for automotive industrial applications, some need high strength, while some may need high thermal capability, fatigue resistance, corrosion resistance and/or wearing resistance. These need different alloy systems to meet one or more requirements for industrial applications. 2) High melting point alloy systems The greatest efforts of developing SSM processes historically are on alloys with relatively low melting Q. ZHU, et al/Trans. Nonferrous Met. Soc. China 20(2010) s1042-s1047 s1046 points such as aluminum and magnesium alloys. Some efforts and success have been achieved on high melting point alloys such as steels34, but further studies are desirable to develop material systems of cast iron, steels and nickel base alloys. These materials have significant higher density than aluminum and magnesium alloys, so there is greater potential to save more weight of automotive components, and thus more fuel economy, and to improve durability by quality and property improvement in terms of SSM processes than for light alloys. 3) Complex geometric components Complex geometry of some automotive components, such as compressor wheels of a turbocharger and cylinder head in an engine, makes it difficult to achieve the stringent property requirements in cast and efficiency/cost in machining from forged billets. SSM has, therefore, great potential to manufacture complex geometric components. The very low shear strength of alloys at semi-solid status makes it achievable to manufacture complex geometric components when a proper design of runner system and die configuration can be achieved in accommodating the low shear strength but relatively high compressive strength. 4) Cost reduction of current SSM components Cost reduction of manufacturing components has been achieved using SSM process over machining from forged billets. However, due to the high cost of manufacturing raw material bar stock, complexity of runner system and die configuration as well as relatively high process costs, the costs of SSM components are still significantly higher than those of casting. Therefore, efforts should be made to further achieve cost reduction of raw material bar stock, of design and manufacture of runner system and die configuration and of processes. 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