ABSTRACT

To improve the yield strength of powder metallurgy steel, this work investigated the effect of a Cu-rich networked phase. Mixtures of 0.7% graphite and Fe–3% Cu hybrid-alloyed steel powders, composed of pre-alloyed Fe–3 x % Cu particles with diffusion-bonded 3(1 − x) % Cu (0 ≤ x ≤ 1), were processed by high-density compaction and conventional sintering. The maximum values of 0.2% proof stress (YS) and ultimate tensile strength (UTS) were obtained at x = 0.68, where high-density compact with well-networked Cu-rich ferrite phase was developed without Cu growth. Moreover, nanosized ϵ-Cu precipitates were observed in the Cu-rich ferrite. These high YS and UTS were achieved not only by decreases in porosity but also by precipitation strengthening caused by the nanosized ϵ-Cu in the Cu-rich ferrite network.

摘要

为了提高粉末冶金钢的屈服强度，这项工作研究了富铜网络相的影响。0.7％的石墨和Fe-3％Cu的混合合金化钢粉的混合物，组成预合金化的Fe-3 X％的Cu粒子扩散结合的3（1 -  X）％的Cu（0≤  X  ≤1），分别为通过高密度压实和常规烧结加工而成。在x  = 0.68时获得了0.2％屈服极限（YS）和极限抗拉强度（UTS）的最大值，在这种情况下，形成了具有良好网络化的富Cu铁素体相的高密度压坯，而没有Cu的生长。而且，纳米sized在富含铜的铁素体中观察到-Cu沉淀。这些高的YS和UTS不仅是通过降低孔隙率来实现的，而且还可以通过富铜铁素体网络中纳米尺寸的ϵ -Cu引起的沉淀强化来实现。