A Combined Powder Metallurgical Approach to Process Gamma-TiAl with Composite Structure
A Combined Powder Metallurgical Approach to Process Gamma-TiAl with Composite Structure
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DOI：
10.1007/s11661-022-06703-4
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发表时间：
2022-05
期刊：
影响因子：
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通讯作者：
R. Gao;H. Peng;H. Guo;B. Chen
中科院分区：
文献类型：
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作者：
R. Gao;H. Peng;H. Guo;B. Chen
采用复合结构设计的 Gamma-TiAl (> 99 pct) 样品是通过 SEBM 胶囊和 HIP 的组合粉末冶金方法制造的。采用选择性电子束熔化 (SEBM) 来制造预烧结粉末床、复合材料结构和胶囊，然后在 1250 °C 下进行热等静压 (HIP)。等离子旋转电极 (PREP) 和气体雾化 (AA) 处理的粉末的混合物，分别具有较高的 (49.66 at. pct) 和较低的 Al (47.61 at. pct) 浓度，成功地用于跟踪从粉末到块状样品的转变，为阐明微观结构形成机制提供了丰富的信息。选择性熔化产生的复合结构由细小的等轴γ晶粒组成，而粉末床的其余部分仅经过预热，然后进行热等静压，其特征在于三重微观结构。这种独特的微观结构（主要由粗γ晶粒和细γ晶粒以及先前的颗粒边界（PPB）组成）的形成机制与Al浓度相关。富铝粉末转变为粗大的 γ 晶粒，而贫铝粉末则形成了含有 PPB 的细小 γ 晶粒。这一发现表明，可以通过增加新生粉末中的铝浓度来消除有害的 PPB。在热处理后的条件下（1350°C），没有发现 PPB，这表明热处理有利于消除 PPB。对于设计的复合材料结构，有证据表明硬区域和软区域的理想分布，与复合结构相关的细γ晶粒负责高硬度区域。
Gamma-TiAl (> 99 pct) sample with composite structural design was fabricated by a combined powder metallurgical approach of the SEBM capsule and HIP. Selective electron beam melting (SEBM) was used to create the pre-sintered powder bed, composite structure and the capsule, followed by hot isostatic pressing (HIP) at 1250 °C. A mixture of plasma rotating electrode (PREP) and gas atomization (AA) processed powders, with the respective higher (49.66 at. pct) and lower Al (47.61 at. pct) concentrations, was employed successfully to track the transition from powder to bulk sample, providing enriched information to elucidate the microstructure formation mechanism. The selective melting created composite structure consisted of the fine equiaxedγ-grains, while the rest of the powder bed that had been subjected to preheat only and then HIP was characterized by the triple microstructure. Formation mechanisms of such unique microstructure, consisting of primarily the coarseγ-grains and fineγ-grains with the previous particle boundaries (PPBs), were correlated to the Al concentration. The Al-rich powder was transformed into the coarseγ-grains, while the Al-depleted powder was responsible for the fineγ-grains with the PPBs. This finding suggests that the detrimental PPBs can be eliminated by increasing the Al concentration in the nascent powder. In the post-heat treated condition (1350 °C), no PPBs was found, suggesting that heat treatment is beneficial by eliminating the PPBs. For the designed composite structures, there was evidence to suggest desired distribution of the hard and soft regions, with the fineγ-grains associated with the composite structure being responsible for the high hardness region.