外文翻译-汽车发动机活塞材质的选取及发展趋势

1、附录：英文技术资料及其翻译 1.中文翻译汽车发动机活塞材质的选取及发展趋势活塞被称为发动机的心脏。它是发动机中最重要的零件之一。其功用是承受气体压力，并通过活塞销传给连杆驱使曲轴旋转。在发动机工作时，活塞直接与瞬时温度2200摄氏度的高温气体接触，其顶部温度达3008，且温度分布不均匀;在做功行程时活寨顶部承受着很大的气体压力，汽油机达4MPa一5MPa，柴油机高达8MPa一9MPa ，甚至更高;此外，活塞在气缸内往复运动线速度可达，l1m/s一16m/s;在这种恶劣的条件下工作。活塞承受着高温、高压的热负荷和机械负荷。因此活塞作为汽车发动机中传递能量的一个非常重要的构件，对其材料具有特殊的要

2、求:密度小、质量轻、热传导性好、热膨胀系数小;并具有足够的高温强度、耐磨和耐蚀性能、尺寸稳定性好。另外还应具有容易制造、成本低廉的特点。伴随着汽车发动机的不断发展与进步，人们对活塞材料的研究与应用也取得了长足的发展。铝合金活塞材料的发展应用概况 世界上最旱的汽车发动机活塞是铸铁的。1911年，铝合金材料以其质轻、良好热传导性以及较低的热膨胀系数等特点的得到人们的关注并开始用于制造活塞。1920年一种Al-Cu-NI-Mg系合金正式成功地应用于汽车发动机活寨，从而证明了铸造铝合金作者简介:1、Al-Cu-NI-Mg系合金 该系合金于1920年开始就在英国得到应用。其典型合金代号有LMI4(英)、

3、SAE39美)、AC5A(日)。该类合金的优点是良好的高温强度、导热性、延伸率及耐磨性;但囚其线膨胀系数和密度较大，铸造性能差且含有较多贵重金属价格较贵而被淘汰。2、Al-Cu-Si系合金 这类合金的优点是:由于含有一定量的硅，铸造性能较好，切削加工性能一也有所改善;在常温和高温下均有较好的机械、物理性能。在70年代之前，该类合金曾是前苏联等国应用最广泛的一种材料，我国的解放牌CAIOA,CAIOB,CAIOC型汽车活塞一也采用此合金。其典型合金代号有SAE300(美)、A110B(俄)、AC2A(日)。该类合金的缺点是:线膨胀系数较大，因含有较多的Cu，所以体积稳定性不好，会产生永久性“长大

4、”现象引起活塞“咬缸”，所以国内现已停止使用这类材料。3、AI-Si合金 由于AI-Si合金线胀系数小、比熏小，耐磨性好，铸造性能好等一系列优点而成为应用于现代发动机活塞制造最广泛的材料。这类合金按含Si量的高低可分为共(业)晶型和过共晶型两大类。4、共晶(亚共晶)型AI-Si合金 国内外轻、巾型汽车汽、柴油发动机以及轿车发动机活塞大多采用了共晶(亚共晶)型AI-Si合金。具有代表性的共晶(亚共晶)型AI-Si合金活塞材料的牌号及化学成分见表1。该类合金含I量一般在8.5%一13%，为了提高合金的室温及高温性能在其中加入了Cu Mg Mn Ni等合金元素进行多元合金化。表2所列为共晶(亚共晶)

5、型Al一Si合金活塞材料常温和高温性能。 合金中的Cu可提高合金的常温及高温强度，改善合金切削加工性能及表面光洁度;但Cu量过多会使合金密度增大，热裂倾向增大，耐蚀性降低，铸造性能变坏，同时还使合金成本增加。囚而作为活塞用的AI-Si合金应在保证其强度的前提下尽川一能降低含铜量。 Mg也是AI-Si合金中提高合金强度的重要元素，特别是与CU配合使用时可进一步提高合金耐热性。但Mg加入量过多时易在晶界上形成脆性相，反而降低了合金强度。另外Mg还可能造成铸件夹渣，所以Mg的加入量一般控制在0.4%一1.5%。国内厂家多控制在0.7%一1.0%之间。 Mn可以提高合金的热稳定性、高温持久强度和使度，

6、同时还闺一以减少杂质元素对铁的危害。但加入过多的Mn会形成粗大脆性化合物，反而降低合金强度。Mn的加入量多控制在1%以下。 国外资料认为。Ni可以提高合金的高温强度及合金热稳定性。如含有Ni的ZLI09比不合Ni的ZLI08体积稳定性好。这对活塞这种零件来说是非常有意义的。但近年来的一些试验研究又表明:加Ni对合金的高温性能并无显著提高 国内外汽车发动机活塞材料的发展及应用 由于铝硅合金中Si含量超过6%一8%时，组织中便会出现粗针状共晶硅组织，使合金的机械性能降低。因此，共晶(亚共晶)型AI-Si合金需进行变质处理。共晶硅常用的变质元素有Na Sr P Sb RE等，其中国内应用较多的是Na

7、盐变质，效果良好。但Na款变质有效时间较短。同时还会腐蚀增竭给生产带来不便。Sr有较强的变质作用和足够·长的变质有效期，但r较贵且变质时会增加合金吸气，故目前还不能取代Na。目前，对于共晶型I-i合金来说(如ZLID9更多地采用了磷变质剂以代替Na变质，且磷变质效果优于Na盐变质而被国内众多活塞制造厂推广使用。现在在汽车发动机上应用最广泛的AI-Si.活塞材料为ZLIQ9（GMahlel24,AC8A),国外著名发动机制造厂(如Cummins Renault等)和国内玉柴、锡柴等发动机制造厂均采用该材料制造的活塞。共晶型AI-Si合金 随着发动机对功率、扭矩、噪声、排放的要求越来越高

8、，共晶(亚共晶)型AI-Si合金已难以达到使用性能要求。因此，人们把目光投向另一种更为理想的活塞材料过共晶型AI-Si合金。这类合金含Si量高达17%一26%，而随着Si含量的增加，合金的线胀系数减小，耐磨性和体积稳定性相应提高，且合金密度也随之减小，用其制造发动机活塞，可在设计上缩小气缸筒内壁与活塞之问的问隙，从而提高发动机效率.因此受到世界各国研究者的重视3国外对过共晶型AI-Si合金的研究应用较早，使用范围已从摩托车活塞扩大到载货汽车的活塞上。国内近些年也对该类活塞材料进行了大量的研究，但实际应用的还较少。国内外具有代表性的过共晶AI-Si合金牌号及化学成分见表3。表4为过共晶型AI-S

9、i合金活寨材料常温和高温性能对比。过共晶型活塞合金按Si的含量分为三组:组一为17%一19%，组二为20%一23%，组三为24%一26%。一二组工艺性较好，在实际生产中应用较多;第三组由于si含量高，结晶范围大，铸造工艺性能很差，初晶Si的变质困难。为保证合金满足活塞性能要求。也在其中加入Cu、Mg、Mn Ni Ti RE等等.所起作用与共晶型合金中基本相同。 新型铝合金活塞材料的研究及应用 美国航空航天局(NASA)马歇尔空间飞行中心(MSFC)两位美籍华人科学家发明了一种名为MS-FC-388高强度铝合金，用于制造EvinrudeE一下TECTM外置发动机活塞，取得了十分令人满意效果与经济

10、效益。其特点是:发动机的噪声大幅度下降，排放的污染显著减少，燃料效率大为提高，使用寿命显著延·长，比普通的常规活塞铝合金的强度高1.5倍，生产材料成本比常规合金的低2.21美元/Kg，在260370仍有令人惊奇的强度。该新型铝合金不但满足汽车工业低排放污染物的要求，而且能满足航天器在高温下有很强的耐腐蚀性的要求。此外，国外许多发动机制造商采用锻造铝合金2618(LD7)用于制造各种高级轿车及赛车发动机活塞。图4所示为应用于Ford发动机上的锻造活塞，图5为Chrysler汽车发动机锻铝活塞。 国内外汽车发动机活塞材料的发展及应用 铝基复合材料的研究及应用 在满足内燃机轻量小型化、可靠

11、性和耐久性的情况下，发动机向着高速、大功率、大压缩比的方向发展，其燃烧室内温度和压力变得更高，以往使用的铝合金已达到或接近使用极限。为此，铝基复合材料活塞的开发近年来受到了高度重视4美、日及欧洲工业发达国家在这方面已取得了重要进展，并在车用柴油机上迅速得到了推广。1)碳化硅颗粒增强铸铝活塞 粒度为5um-10um，含量为5%一7%的SIC陶瓷颗粒，经过特殊处理后用流变铸造法加入到ZL I中然后挤压铸造成型，可用于活塞的整体或局部增强。该材料的热导率及热膨胀系数各为0. 32w/(m和18x10-6/C)。国内研制的碳化硅颗粒局部增强铝合金活。 塞经上海50型拖拉机田间试验证明，第一道环槽导热得

12、到了较大改善，燃烧喉口得到加强，耐磨性比镶奥氏体铸铁圈的活塞要好，活塞质量也得到了加强。2)氧化铝、硅酸铝和硼酸铝短纤增强铝合金活塞(CFR) 该材料采用陶瓷纤维氧化铝或硅酸铝、硼酸铝短纤维增强基体材料(一般为共晶性或亚共晶性Al一Si合金)的活塞(CFR活塞)，与基体铝合金相比，在300时的抗拉强度极限提高20%以上，热膨胀系数降低15%，导热率降低25%，而密度基本不变，耐磨性能优异，热稳定性好、具有更好的高温综合性能6。采用挤压铸造工艺生产的局部增强复合材料活塞，界面结合牢固可靠，成品率高，工艺宽容好，特别适合于经增压、强化的工作条件苛刻的柴油发动机。目前，硼酸铝单晶纤维团粒化坯体，强化

13、活塞第一道环槽和顶部的二冲程汽油机用铝基复合材料活塞，已经在舷外机和摩托雪橇上得到了应用。国外日本丰田ART公司以年产C FR活塞达百万只ll:国内东南大学材料学院与跃进集团及南京金陵汽车配件厂合作的NJ433发动机采用增强基体材料的活塞，通过了1000小时台架试验;与玉柴机器公司、德国马勒(南京)公司合作的YC6112发动机活塞顶部燃烧室周边增强，现已通过一系列试验及技术鉴定并达到批量化生产，迄今已经生产复合材料活塞毛坯20万件。形成年产数千万元的复合材料活塞产业，使陶瓷纤维增强铝基复合材料在我国的汽车发动机行业进入了工业应用阶段。3)国内外其它活塞材料的研究应用 随着大马力汽车发动机快速发

14、展，尤其是重型柴油发动机涡轮增压、中冷技术的应用以及大缸径高压缩比、低排放要求的不断提高。传统铝合金活塞材料已无法满足其使用要求，因而国内外众多活塞材料研究机构和制造商推出了许多新型活塞材料。钢顶铝裙材料 与铸铝和比，铸钢的机械强度高、耐磨性能好，但加工麻烦，密度大，成本高，对缸套的磨损严重。因此很少全部用铸钢做活塞，而是在一些强化程度高的柴油机上用铸造合金钢(如40CrMn, 4CrlDSi2Mo)做活塞头部，用铸铝做活塞裙部，从而构成了所谓的钢顶铝裙的组合式活寨。该结构的活塞已经在超长冲程的L-G/GBE系列的低迷发动机上得到了应用。法国Renault公司制造的重型商用车用420马力dil

15、l发动机也采用了这种结构的活塞。图6所示为德国Mahel活塞有限公司制造的重型商用车用钢顶铝裙的组合式活塞。陶瓷材料 陶瓷是各种氧化物、氮化物、碳化物等无机非金属材料的通称。全陶瓷活塞目前还无成功的应用实例，但织合式陶瓷活塞已在特种发动机上得到了一定的应用。五十铃汽车公司所研制的绝热发动机已运行了3500h。据介绍，它的活塞是采用Si3N4活塞头部，用一钢卡环与铸铁裙部连接，头部与裙部之间设置空气隙，并安装一隔热衬垫。这种设计的活塞隔热效果较佳，头部最高温度为700，裙部却只有100200。但由于陶瓷的性能特点、复杂的制造技术和高成本，要使陶瓷活塞大规模地应用于内燃机，还需要做许多研究工作。树

16、脂基复合材料 树脂基复合材料作为一种新型的工程材料已广泛应用于国民经济的许多领域，如铸造用的玻璃纤维增强塑料模具和军工用的导弹头锥。美国西密歇根大学采用30%短切石墨纤维增强聚酞业胺树脂基复合材料(260下抗拉强度可达102MPa，延伸率仅为7.2%)制造活塞。囚此材料的耐热温度较低，故在活寨顶部等离子喷涂了一层Mg一A1203尖晶石热障涂层。尔后将该活塞装在了功率为3 .7kw转速为3800r/m的二冲程风冷小型发动机上进行了1500小时台架试验。尽管活塞顶部出现烧蚀，但该复合材料在制造小型活塞仍具有一定的生命力。碳及碳纤维增强碳基复合材料 石墨具有自润滑性好、导热率高、耐热性能优良、尺一寸

17、稳定性好、热膨胀系数小、体积密度低等特点。但普通石墨的力学性能不高，使其在活塞材料上一直难于应用。随着等静压成型技术和细结构高强度石噩的发明，综合性能良好的高强度石墨材料在活塞上的应用才真正具有了可能性和现实性。碳纤维增强碳基复合材料除了石墨材料所具有的一切理化性能外具有最优异的高温性能在1700C的惰性环境下抗弯强度为571.9MPa。美国赛车公司在2 .4KW发动机32小时全负荷性能台架试验中发现碳纤维增强碳基复合材料的活塞明显优于铝合金活寨，且活塞顶面完好无损。其成本分析报告指出:按年产25万只碳基复合材料的活塞计算.每只活塞成本为14美元，如果将年产量扩至100万只则单只活塞成本可降到

18、9.1美元，而铝合金活塞的单只成本为6一12美元，由此一可见，碳基复合材料活塞有着广阔的应用前景。结束语 现代道路交通设施的完善以及物资流通速度的加快促使汽车工业制造出快速、高效的交通运输工具而对汽车发动机提出了更高的要求:提高发动机转速和功率一活塞工作速度达11m/s16m/s，功率达到450马力或更高。随着汽车发动机向高速化、大功率方向的发展，活塞材料除对常温强度、使度、延伸率、热膨胀系数等性能要求不断提高外，还对其高温性能(如高温拉伸强度、高温疲劳强度、导热率)及耐磨性能提出了更高的要求。因此合理选择活寒制造材料对于新型发动机的开发至关重要。 对于轻、中型汽车及轿车用发动机来说，共晶(亚

19、共晶)AI-Si合金以其良好的材料综合性能仍然是制造活塞的首选材料;对于重型大马力发动机而言，钢顶铝裙材料的活塞已经得到大量应用，而在众多活塞新材料中过共晶Al-Si合金、铝基复合材料以及碳纤维增强碳基复合材料均以其优良的材料综合性能以及关键技术的突破、逐步降低的制造成本等优点而最具发展前途。2.英文技术资料 Automobile engine piston material selection and development trend The piston is called the engine's heart. It is the most important parts in

20、 the engine of one. Its function is withstanding gas pressure, and driven by the piston pin to crankshaft connecting. When the engine work directly with transient temperature, the pistons 22 degrees Celsius temperature gas contact, the top temperatures reached 3008 and temperature distribution uneve

21、n; In power stroke ZhaiDing department live under a lot of gas pressure, 4MPa a gasoline engine 5MPa, diesel engine of 8MPa a 9MPa, as even higher; In addition, the piston cylinder reciprocating movement in linear can reach, l1m/s a dedicated 16m/s; In this harsh conditions work. The piston under hi

22、gh temperature and high pressure the heat load and mechanical load. Therefore the pistons as automobile engine transmission of energy a very important component of its material, has special requirements: density is small, light quality, thermal conductivity, good thermal expansion coefficient little

23、; And have enough of the high temperature strength, wear and corrosion resistance, dimension stability is good. Also should have easy to manufacture and cheap characteristics. With the continuous development of automobile engine with progress, people on the research and application of the piston mat

24、erial have also made considerable development. The development and application of aluminium alloy piston material profiles The world's most drought car engine piston is cast iron. In 1911, aluminum alloy material with its light, good low thermal conductivity and characteristics of thermal expans

25、ion coefficient of the focus of people's attention, and began to get used to manufacture the piston. 1920 a Cu Al - NI - Mg department alloy - officially applied successfully in the automobile engine village, so as to prove the live cast aluminium author introduction:1, Cu - NI Al - of Mg alloy.

26、 The department alloy in 1920 start applied in Britain. Its typical alloy code LMI4 (English), there SAE39 beauty), AC5A (date). This alloy is the advantage of good high strength, thermal conductivity, elongation and wear resistance; But its expansion coefficient and the density of the prisoner larg

27、er, casting performance is poor and contain more precious metal price is more expensive and be eliminated.2, Cu - Si Al - of alloys This kind of alloy advantage is: because it contains a certain amount of silicon, casting performance is better, machinability a also improved; In normal temperature an

28、d high temperatures are good mechanical and physical properties. In the 1970s, this alloy was before the former Soviet union and other countries the most widely used a kind of material, our XieFangPai CAIOA, CAIOB, CAIOC type automobile pistons also USES this alloy a. Its typical alloy code have SAE

29、300 (USA), A110B (Russia), AC2A (date). This alloy steels are defect is: larger, because contain more Cu, so volume stability is bad, will produce permanent "grow up" phenomenon caused by the piston "bite cylinder", therefore the domestic has stopped using this kind of material.3

30、, AI - Si alloys Because the AI - Si alloy linear expansion coefficient than fume small, small, good abrasion resistance, casting performance and so on a series of advantage and be used in modern engine pistons manufacturing the most extensive materials. This kind of alloy according to the discretio

31、n of containing Si quantity can be divided into altogether (industry) crystal and eutectic type two kinds big.4, eutectic (the eutectic) type AI - Si alloys Domestic and international light, towel type car gasoline and diesel engine and car engine piston is used mostly the eutectic (the eutectic) ty

32、pe AI - Si alloys. The typical eutectic (the eutectic) type AI - Si alloy piston material grades and the chemical constituents see table 1. These alloys containing I quantity in 8.5% a 13%, general to improve performance and high temperature alloy in which joined Cu Mg alloy elements such as Ni Mn m

33、ultivariate alloying. Table 2 listed eutectic (the eutectic) type piston material Al a Si alloy normal temperature and high temperature performance. The alloy can improve the Cu alloy is normal and high temperature strength, improve the alloy cutting processing properties and surface finish; But too

34、 Cu amount will make alloy density increases, hot tear tendency increases, corrosion resistance is reduced, casting performance becomes worse, also make alloy costs. And as a prison with AI - Si piston in guarantee its strength alloy should be under the premise of a can reduce as sichuan contain cop

35、per quantity. Mg is AI - Si alloy improve alloy strength of importance chemical element, especially when used together with CU alloy heat resistance may be further improved. But Mg addition amount in too easily formed on grain boundary brittle phase, the decline in alloy intensity. Another Mg may al

36、so cause casting slag, so Mg addition amount general control in 0.4% a 1.5%. Domestic manufacturer is much control in 0.7% a between 1.0%. Mn can improve the thermal stability, high temperature alloy lasting strength and make degrees, also 'maiden a to reduce the harm of iron impurity element. B

37、ut to join too many Mn can form bulky brittle compounds, but reduce alloy intensity. Mn's addition amount control under 1%. Foreign material think. Ni can improve alloy temperature strength and alloy thermal stability. If the ZLI09 containing Ni Ni than not ZLI08 volume stability of. The pistons

38、 for this part is very significant. But in recent years that some of the experimental research and to alloy: addition Ni high-temperature performance and no significant improvement Domestic and foreign automobile engine development and application of the piston material Because al-si alloy Si conten

39、t in a more than 6% of 8%, organization will appear thick needle eutectic silicon organizations, the mechanical properties of the reduced. Alloy Therefore, eutectic (the eutectic) type AI - Si alloy need to undertake modification. Eutectic silicon common metamorphic elements have making Sr P Sb RE e

40、tc, with domestic application more is deteriorating, making good results. Salt But making money metamorphic effective time is short. Also will increase to production safflowerfraie corrosion inconvenience. Sr has the strong metamorphism and enough, but the validity, long metamorphism is expensive an

41、d metamorphic when r increased, so is still alloy inspiratory making cannot replace. At present, for eutectic type I - I alloy ZLID9 it (such as more adopted in lieu of phosphorus metamorphic agent making metamorphism, and phosphorus metamorphic effect is better than by making salt metamorphic popul

42、arize the use of domestic numerous piston manufacturer. Now in the most widely used car engine on the AI - Si. ZLIQ9 (piston material GMahlel24, for AC8A), foreign famous Cummins engine manufacturer (such as Renault, etc.) and domestic yuchai, tin wood are used as engine manufacturer the material ma

43、de the pistons.Eutectic type AI - Si alloys With the engine to power, torque, noise, emission requirements more and more high, eutectic (the eutectic) type AI - has been difficult to achieve Si alloy using performance requirements. Therefore, people look to another kind of more ideal piston material

44、 - after eutectic type AI - Si alloys. This kind of alloy contain Si quantity as much as 17% a 26%, and with the increase of the content of Si coefficient of linear expansion, alloy decreases accordingly, wear resistance and volume stability improved and alloy decreases, use with density and the man

45、ufacturing engine piston, can design on the narrowing of the piston and cylinder tube wall, and ask asked gap. Therefore improve engine efficiency by world researchers' attention 3 foreign across eutectic type AI - Si alloy earlier, research and application of use scope has been expanded to bill

46、s from motorcycle Detroit auto piston. In recent years for this type of domestic piston material also done a lot of research, but less is of practical application. Domestic and foreign representative had eutectic AI - Si alloy nameplate and chemical composition table 3. Table 4 for eutectic type AI

47、- Si alloy live village materials normal temperature and high temperature performance comparison. After eutectic type piston alloy press Si content is divided into three groups: group one for 17% a 19%, 20% of a 23%, group redquin three 24% a 26%. 123 group good workmanship, applied in practical pro

48、duction more; The third group, due to high levels of si crystallization casting property range, very poorly, the metamorphic difficult wafer si early. To ensure the alloy meet piston performance requirements. Also in Cu, Mg, added Ti RE etc. Ni Mn role in the alloy crystal and basic and same.New alu

49、minum piston material research and application NASA (NASA) Marshall space flight center (MSFC) two chinese-american scientists invented a called MS - FC - 388 high-strength aluminum alloy, is used to make EvinrudeE once TECTM external engine piston, made very satisfactory effect and economic benefit

50、s. Its features are: engine noise dropped substantially, the pollution significantly reduce emissions and fuel efficiency greatly improved, the service life is long, and, significantly delayed than ordinary conventional piston alloy strength one-and-a-half times higher than the regular cost of mater

51、ials, production of low alloy in $2.21 / Kg, 37 260 are still surprising strength. This new aluminum not only meet the auto industry low emission pollutants requirement, and can satisfy the spacecraft at high temperatures have strong corrosion resistance requirements. In addition, many foreign engin

52、e manufacturers forged alloy 2618 (LD7) used in manufacturing various limousines and racing engine piston. Figure 4 shows is applied to the starting engines for forging the pistons, figure 5 Chrysler car engine forging aluminium piston. Domestic and foreign automobile engine development and applicat

53、ion of the piston materialAluminum matrix composites and application In meet internal combustion engine lightweight miniaturization, reliability and durability, engine under the condition of high speed, high power, big towards the direction of compression ratio, the combustion indoor temperature and

54、 pressure becomes higher, ever the aluminum alloy has used at or near use limit. Therefore, aluminum matrix composites developed in recent years of piston by attaches great importance to the 4 the us, Japan and Europe developed countries in this respect has made important progress, and vehicle diese

55、l engine in rapidly expanded.1) silicon carbide particles reinforced aluminum piston For 10um 5um - size, content to 5% a 7% of SIC ceramic particle, through special processing with rheological casting method after joining ZL I and squeeze casting forming, 'can be used for piston's overall o

56、r local enhancement. The material of thermal conductivity and thermal expansion coefficient for 0. Each 32w / (m and 18x10-6 / C). Domestic development of silicon carbide grain locally enhanced aluminum alloy live. Alessio via Shanghai 50 type tractor field experiment proof, a the ring groove is imp

57、roved greatly heat, burning throat Mouth strengthened, wear resistance than brigandine austenitic iron laps of the piston, piston, quality is enhanced.2) alumina, guisuanlu: and boric acid aluminum alloy piston (CFR staple enhance) This material adopt ceramic fiber alumina or guisuanlu:, short fiber

58、 reinforced aluminum borate substrate material (usually eutectic sex or the eutectic sex a Si alloy) Al piston (CFR piston), compared with matrix in 300 , aluminium alloy of tensile strength limit increased by 20% above 15% reduced thermal-expansion coefficient, thermal conductivity reduce 25%, and

59、density basically unchanged, wear-resisting performance is excellent, good thermal stability, has better high temperature comprehensive performance 6. The squeeze casting process production of local reinforced composites with sturdy and reliable piston, interface, high-yield, craft tolerance is good, particularly suitable f