In the manufacture of sintered steels by metal injection molding (MIM), typical microstructural defects, such as pores and pore agglomerates, phase structure heterogeneities, and boundaries between different phases, are hard to avoid. Such heterogeneities cause crack origination, growth, and propagation when sintered materials are subjected to mechanical loads. The crack propagation path and fracture resistance are associated with the complex heterogeneous structure including ferrites, cementites, martensites, pores, and weak interfaces. With increasing sintering times, metal grains grow rapidly, leading to brittle fracture of the samples. Subsequent heat treatment substantially decreases the grain size and changes brittle fracture to ductile one. Multicycle sintering of the Catamold 8740 low-alloy steel greatly increases the impact strength of V-notched samples (from 7.55 to 13.95 J/cm²). Greater density of the samples and fewer stress concentrators favorably influence the material’s capability to withstand impact loads. Thus when density of the billets following six sintering cycles increases by 2.5%, their impact strength becomes 1.8 times higher. With a greater number of sintering cycles, the ductile dimples become significantly larger, while the increase in shock impact and density of the sintered material gradually slows down. The grain size substantially increases (in turn, suppressing pore healing) and density of the samples becomes greater over the total sintering time. X-ray diffraction and spectral analysis revealed additional phases after sintering and heat treatment. Additional fine-crystalline carbide and oxide phases become more distinguished with further increase in the sintering temperature and heat treatment. Brittle inclusions, along with residual porosity, present in sintered steel decrease the dynamic properties of the material.

在通过金属注射成型（MIM）来制造烧结钢时，很难避免典型的微观结构缺陷，例如孔和孔的团聚体，相结构的异质性以及不同相之间的边界。当烧结材料承受机械载荷时，这种异质性会导致裂纹的产生，扩展和扩展。裂纹的扩展路径和抗断裂性与复杂的异质结构有关，包括铁素体，渗碳体，马氏体，孔隙和弱界面。随着烧结时间的增加，金属晶粒快速生长，导致样品脆性断裂。随后的热处理大大减小了晶粒尺寸，并将脆性断裂变为韧性断裂。^2个）。更高的样品密度和更少的应力集中器有利地影响了材料承受冲击载荷的能力。因此，当六个烧结周期后的钢坯密度增加2.5％时，其冲击强度将提高1.8倍。随着烧结次数的增加，韧性凹痕变得更大，而冲击冲击的增加和烧结材料的密度逐渐减慢。在整个烧结时间中，晶粒尺寸显着增加（进而抑制了孔的愈合），并且样品的密度变得更大。X射线衍射和光谱分析揭示了烧结和热处理后的其他相。随着烧结温度和热处理的进一步提高，额外的细晶碳化物和氧化物相变得更加明显。