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众所周知,Ni_3Si金属间化合物在硫酸中的耐蚀性很好,但由于组成范围狭窄,容易产生偏析,用冶炼法制成的Ni_3Si成形材存在很多脆性γ相(Ni_5Si_2),热加工性恶化,成形发生困难。为了使这种难加工性的材料成形,人们开发了利用MH法的粉末冶金法,即在保留很多易加工成分的α相(Si在Ni中固溶)状态下立即进行热成形加工,然后热处理使其β相(Ni_3Si)单相化(即含有少量α相的α相弥散β相组织)。利用这种方法得到机械性能和耐硫性能都良好的77.5mol％Ni—22.6mol％Si的
It is well known that the corrosion resistance of Ni_3Si intermetallic compound in sulfuric acid is very good, but due to the narrow composition range, it is easy to produce segregation. There are many brittle γ phase (Ni_5Si_2) in the Ni_3Si forming material prepared by the smelting method, the hot workability is deteriorated and the forming takes place difficult. In order to shape such a difficult-to-process material, the powder metallurgy method using the MH method has been developed that immediately undergoes thermoforming in an α phase (Si is dissolved in Ni) that retains many easily-worked components, and then heat-treated So that the β phase (Ni_3Si) single-phase (that contains a small amount of alpha phase α-phase dispersed β-phase organization). By this method, 77.5 mol% of Ni-22.6 mol% Si having good mechanical properties and sulfur resistance