Yu-po took the first game 21-17 but world number 12 Zhang fought back to rattle through the next two games 21-6, 21-9 in a total of 44 minutes at the Saarlandhalle in the German city of Saarbrücken.

She will now face second seed and world number 15 Nitchaon Jindapol of Thailand, who managed to see-off the challenge of China's fourth seed and world number 16 Chen Xiaoxin 21-14, 21-16 in 40 minutes.

In the men’s singles draw, Chinese Taipei’s Hsu Jen Hao, the fourth seed and world number 35, is through to the final after a bruising battle with The Netherlands' Mark Caljouw 21-15, 16-21, 21-14 in 64 minutes of see-saw action.

He will now face Denmark's unseeded Rasmus Gemke, the world number 60, who wasted little time in seeing off the challenge of Malaysia's 14th seed Lee Zii Jia.

Bulgarian top seeds Gabriella Stoeva and younger sister Stefani Stoeva were sent tumbling out of the women's doubles after losing 21-17, 21-11 to Japan's Akane Araki and Aoi Matsuda.

Second seeds Thailand's Jongkolphan Kititharakul and Rawinda Prajongjai came through against China's Du Yue and Xu Ya 21-15, 21-14 in 41 minutes.

Indonesian pair, the fourth seeds, Fajar Alfian and Muhammad Rian Ardianto, edged out Danish duo and fifth seeds Mathias Christiansen and David Daugaard 15-21, 21-16, 22-20 in 63 minutes.

The tournament concludes tomorrow.