Trends and Challenges in Lead-Free Brass Alloy Development for Machining Applications: A Systematic Literature Review

Lead (Pb) is widely used in brass alloys (Cu–Zn) to enhance machinability, as its deformation into needle-like particles promotes chip breakage by initiating cracks. However, growing awareness of Pb’s toxicity has led to strict environmental regulations and growing demand for sustainable, lead-free alternatives. This systematic review, conducted following the PRISMA 2020 framework, consolidates recent research on the development and performance of machinable lead-free brass alloys. A comprehensive search was performed in the Web of Science, ScienceDirect, and Scopus databases, identifying 93 studies for full-text analysis. Various strategies have been identified for the development of lead-free brass, including process optimization, heat treatments, direct Pb substitution, and novel alloy design. The review highlights significant progress in achieving acceptable mechanical and machining performance, although trade-offs in cost, corrosion resistance, and large-scale manufacturability remain. The consolidated key findings offer a structured basis for future alloy design and promote consistent evaluation of microstructural, mechanical, and machining properties.