We assume that the ultrahigh hardness is mainly due to the ultrafine grains, high density dislocation and more content of carbon in martensite.

研究分析表明，晶粒细化、高的马氏体含量、马氏体高位错密度和固溶含碳量是获得超高硬度的主要原因。

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The results show that P/M valve seats using this technology has high density and high carbon content , and their microstructure are martensite , bainite and network carbide.

结果表明，采用该工艺可获得高密度、高碳含量、具有马氏体、贝氏体和网状碳化物组织的粉末冶金气门座。

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Observations showed that the micro-structure of the steel after forging or high temperature rolling was composed of low-carbon martensite, a little part of bainite and residual austenite.

微观组织观察表明，在锻造或高温轧制状态下获得了以低碳马氏体为主，含少量贝氏体和残余奥氏体的复合组织。

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